InspectAPedia.com InspectAPedia®
Google
InspectAPedia
 

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

  • HOME
  • AIR CONDITIONING
  • DAMAGE ASSESSMENT
  • ELECTRICAL
  • EXTERIORS
  • HEATING
  • HOME INSPECTION
  • INTERIORS
  • PLUMBING
  • ROOFING
  • SEPTIC SYSTEMS
  • STRUCTURE
  • WATER SUPPLY
  • ENERGY SAVINGS
  • ENVIRONMENT
  • INDOOR AIR IAQ
  • INSULATION
  • MOLD INSPECT TEST REMOVE
  • NOISE
  • ODORS
  • SOLAR ENERGY
  • VENTILATION
  • EXPERTS DIRECTORY
  • CONTACT US



InspectAPedia ® Home

WATER HEATERS

AGE of WATER HEATERS
AIRBOUND HEAT SYSTEM REPAIRS
ALTERNATIVE HOT WATER SOURCES
  ELECTRIC SHOWER HEATERS
  High Efficiency Water Heaters
  Indirect-fired Water Heaters
  Instantaneous Water Heaters
  Multiple water heaters in parallel
  Multiple water heaters in series
  Range Boiler Water Heaters
  Side Arm Coil Water Heaters
  Solar Water Heaters
  Tankless Coil for Hot Water
  Tankless Water Heaters
ANODES & DIP TUBES on WATER HEATERS
ANTIFREEZE for BOILERS
ANTI SCALD VALVES
  Define Mixing Valves, Anti Scald Valves
  Table of Scalding Temperatures & Times
  Hot Water Anti-Scald Regulations
  How Anti Scald Valves Work
  Installing & Setting Anti-Scald Valves
  Which Way To Turn the Mixing Valve
  Using a Manual Hot Water Tempering Valve
  Built-in Fixture Anti-Scald Valves
  Mix Valve Improves Hot Water Quantity
  Inspect Anti-Scald Valves
ANTI SCALD VALVE PROTECTION, Best Practices
  Water Pressure-Balancing Valves
  Thermostatic Mixing Valves
  Retrofits to Avoid Scalding Burns
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
  Aquastat control HI LO settings
  Aquastat control DIFF settings
  L7224U Universal Aquastat
  Single Function Limit Switches
  Strap-On Limit Controls

BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER VALVE, HEATING SYS
BACKFLOW PREVENTER, HEATER WATER FEEDER
BACKUP HEAT for HEAT PUMPS
BLEVE EXPLOSIONS
BOILERS, HEATING

CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CHEMICAL CONTAMINANTS in WATER
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CLOGGED DRAIN DIAGNOSIS & REPAIR
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING

DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK

ELECTRIC WATER HEATERS
  Electric, Gas, Oil Water Heater Efficiency
  ELECTRIC SHOWER HEATERS
  Electric Water Heater Checklist
  Electric Water Heater Controls List
  Electric Water Heater Element Replacement
  Electric Water Heater Element Tests
  Electric Water Heater High Temp Cutoff Test
  Electric Water Heater Repair Guide
  Electric Water Heater Reset Switch
  Electric Water Heater Thermostats
  Electric Water Heater No Hot Water
  Electric Water Heater Parts Identification
  Electric Water Heater Reset & Temp Set
  Hot Water Temperature & Pressure Valve
  Timers for Electric Water Heaters
  Water Heater Anode & Dip Tube Check

FLOODED HEATING EQUIPMENT REPAIR
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
FROST HEAVES, FOUNDATION, SLAB

GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
  DRAFT HOODS - gas fired
  Gas BTUH & Cubic Feet
  Gas Conversion LP Natural Gas
  GAS PIPING, VALVES, CONTROLS
  SOOT on OIL FIRED HEATING EQUIPMENT
  SPILL SWITCHES - Flue Gas Detection
GAS PIPING, VALVES, CONTROLS

HEAT TAPES, Heat, Insulation prevent Freeze-Up
HEATING COST FUEL & BTU Cost Table
HEATING COST SAVINGS METHODS
HEATING SYSTEMS

HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
  Alternative Hot Water Sources & Methods
  Anti-Scald Valves & Hot Water Quantity
  CLOGGED PIPING & Hot Water Flow
  Extra Tanks to Increase Hot Water
  Insulate Hot Water Piping
  Insulate Hot Water Tank?
  Larger Diameter Water Supply Piping
  Water pipe clog diagnosis
  Water pipe clog repair guide
HYDROGEN SULFIDE GAS

INDIRECT FIRED WATER HEATERS

MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES

NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE / SOUND DIAGNOSIS & CURE
NOISE CONTROL for HEATING SYSTEMS
NOISE, PLUMBING CHECKLIST
NOISE, WATER HEATER

ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
OIL & GAS PIPING
OIL FIRED WATER HEATERS
  DRAFT MEASUREMENT, CHIMNEYS & FLUES
  DRAFT REGULATORS, DAMPERS, BOOSTERS
  OIL BURNERS
  OIL BURNER NOISE SMOKE ODORS
  OIL TANK PIPING & PIPING DEFECTS
  OIL TANKS

PIPING IN buildings, Clogs Leaks Types
PLASTIC HEATER VENT

RADIANT HEAT
RANGE BOILERS
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks

SAFETY, HEATING INSPECTION
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection

TANKLESS COILS
TANKLESS WATER HEATERS
Temperature Pressure Relief Valves - Water Heaters
THERMOSTATS, HEATING / COOLING
THERMOSTATS, WATER HEATER
  AQUASTAT CONTROL Functions
  Electric Water Heater Thermostats
TIMERS for ELECTRIC WATER HEATERS

VALVES, PLUMBING

WATER CONTAMINANT LEVELS
WATER HAMMER NOISE DIAGNOSE & CURE

WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISES
  Water Heater Flush Procedure
  WATER HEATER SCALE - De-Liming Procedure
  Water Heater Scale Prevention

WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER PROPERTIES
  Electric, Gas, Oil Water Heater Efficiency
  Water Heater Life Expectancy Comparisons
  Water Heater Operating Cost Comparisons
  Water Heater Purchase & Maintenance Costs
  Water Heater Water Quantity Comparisons
  Water Heater Recovery Speed Comparisons
  Water Heater Safety Comparisons
  WATER HEATER EFFICIENCY

WATER HEATER SCALE - De-Liming Procedure
WATER HEATER SCALE PREVENTION
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?

WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE & FLOW MEASUREMENT
  WATER PRESSURE VARIATION CAUSES
  WATER PRESSURE TOO HIGH: DANGERS
  Definition of Static Water Pressure
  Definition of Dynamic Water Pressure
  Measure Municipal Water Pressure
  Measure Pump & Well Water Pressure
  WATER FLOW RATE MEASUREMENT
  HOT WATER PRESSURE EXPANSION RATE
WATER PRESSURE GAUGE ACCURACY
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PRESSURE REDUCER / REGULATOR
WATER PRESSURE PUMP REPAIR GUIDE
WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER PUMP REPAIR GUIDE
WATER PURIFIERS
WATER QUALITY TESTS, CONTAMINANTS, TREATMENT
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING

More Information

Schematic of a sacrificial anode on a hot water tank (C) Carson DunlopHot Water Heater Selection, Inspection, Diagnosis, & Repair Guide
     

  • Water heaters: how to inspect, test, adjust, repair, and choose among types of hot water heaters
    • Guide to inspecting gas fired hot water heaters
    • Guide to inspecting oil fired hot water heaters
    • Guide to inspection of electric water heaters
    • Guide to tankless coils, indirect fired water heaters, range boilers
    • No Hot water? how to get more hot water flow, quantity, performance from your water heater
    • Water heater synonyms: geyser (non-potable water), calorifier (potable water)
    • Water heater tank synonyms: hot water tank, water heater tank, calorifier tank, geyser tank, water kettle, water cauldron, water pot, water copper, domestic hot water, or DHW.
  • ALTERNATIVE HOT WATER SOURCES - separate article
  • HOT WATER PROBLEM DIAGNOSIS - separate article
  • WATER HEATER DEFECTS LIST - separate article
  • Questions & Answers about diagnosing & repairing hot water heaters.
  • References

Click to Show or Hide Related Topics

  • WATER HEATERS - home
  • AGE of WATER HEATERS
  • ALTERNATIVE HOT WATER SOURCES
  • ANODES & DIP TUBES on WATER HEATERS
  • ANTI SCALD VALVES / MIXING VALVES
  • BLEVE EXPLOSIONS
  • DRAIN a WATER HEATER TANK
  • ELECTRIC WATER HEATERS
  • FLOODED WATER HEATER REPAIR
  • GAS FIRED WATER HEATERS & GAS HEATERS, HIGH EFFICIENCY
  • HOT WATER IMPROVEMENTS - home
  • HOT WATER DELIVERY SPEED UP
  • HOT WATER EFFICIENCY IMPROVEMENT
  • HOT WATER PRESSURE EXPANSION RATE
  • HOT WATER PRESSURE LOSS
  • HOT WATER PROBLEM DIAGNOSIS
  • HOT WATER QUANTITY IMPROVEMENT
  • HYDROGEN SULFIDE GAS
  • INDIRECT FIRED WATER HEATERS
  • NOISE, WATER HEATER
  • ODORS IN WATER
  • OIL FIRED WATER HEATERS
  • RANGE BOILERS
  • RELIEF VALVE LEAKS
  • RELIEF VALVES - Water Heaters
  • SCALE REMOVAL, WATER HEATERS & SCALE PREVENTION
  • SOLAR HOT WATER HEATERS
  • TANKLESS COILS
  • TANKLESS WATER HEATERS
  • THERMOSTATS, WATER HEATER
  • TIMERS for ELECTRIC WATER HEATERS
  • WATER HEATER AIR INLET
  • WATER HEATER DEBRIS FLUSH
  • WATER HEATER EFFICIENCY
  • WATER HEATER FLUSH PROCEDURE
  • WATER HEATER PROBLEM DIAGNOSIS
  • WATER HEATER PROPERTIES
  • WATER HEATER SAFETY
  • WATER HEATERS for HOME HEATING USE?
  • WINTERIZE A BUILDING
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Water heater inspection, diagnosis and repair home page. This page contains links to in-depth articles on inspecting, testing, and repairing problems residential hot water heaters of all types, including their parts, controls, and alternative sources for hot water as well as tips for improving hot water temperature, hot water pressure, and hot water quantity. Articles listed here will answer just about any question about domestic water heaters, water heater selection, installation, problem diagnosis, repair, operating cost, or performance. Page top sketch provided courtesy of Carson Dunlop Associates.

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

Water Heater Inspection, Diagnostic, & Repair Guide

Flue gas spillage at gas fired water heater (C) Daniel FriedmanWhile an electric, gas-fired, or oil-fired water heaters, along with tankless coils on heating boilers are among the most common methods for producing domestic or residential hot water for washing and bathing, there are plenty of other ways that people obtain hot water.

All hot water supply systems use some energy source (electricity, oil, gas, solar energy) to heat either a reservoir of hot water stored in a hot water tank, or to heat water as it is used (such as tankless coils and Thermar™ type instantaneous water heaters.)

An exception is geo-thermal hot water (such as is readily available in Iceland and in more localized areas in other countries). And the most common hot water complaint we hear is "how can I get more hot water quantity - I keep running out of hot water" or "how can I get better hot water pressure?"

Our photo shows clear evidence of flue gas spillage from a gas fired water heater. In articles linked from this page we discuss this and other water heater diagnosis and repair topics.

The articles listed below describe the inspection, operation, diagnosis, repair, and improvement of each type of water heater, and we include detailed advice about how to improve hot water supply in buildings as well as inspection and correction of leaks, high hot water costs, odors, noises, and safety problems.

Note that in some parts of the world, such as South Africa, folks use the term geyser for water heater or hot water maker.

Hot water problems and diagnostic guides for all kinds of hot water troubles are summarized at our Hot Water Troubleshooting Diagnostic Guide. You might want to check there to be sure you're fixing the right problem.

Water Heater Basics: Types, Properties, & Inspection Topics for Home Water Heaters

Please see the articles listed at page top or at Related Topics under HOT WATER HEATERS for our complete list of water heater articles.

Have you already checked our Hot Water Trouble Diagnostic Guide?

Before you start fixing or buying stuff to fix a hot water problem hot water problems and diagnostic guides for all kinds of hot water troubles are summarized at WATER HEATER PROBLEM DIAGNOSIS. You might want to check there to be sure you're fixing the right problem. Those questions & suggestions can help point you to the shortest route to troubleshooting hot water complaints like "no hot water" or "not enough hot water".

The following information about residential water heaters is adapted, illustrated, and expanded from the Carson Dunlop Home Reference Book, with generous permission of Carson Dunlop Associates.

Domestic water heaters provide hot water to the faucets and appliances. Most water heaters are conventional storage-type heaters, where heated water is stored in a large tank. There are also tankless systems, where water is heated on demand, either by a boiler, or a dedicated water heater. Indirect water heaters are a third type. They typically have a large tank, with the heat being provided by the boiler that heats the house.

Water may be heated by gas, propane, oil or electricity. Solar water heaters are also available.

Water heaters may be used to heat all, or part of a house, through the use of fan-coil units, or radiant heating. This is called a combination heating system because the water heater provides domestic hot water and it heats the home.

The text below discusses residential electric, gas, and oil fired water heaters and tankless water heaters. Also see
ALTERNATIVE HOT WATER SOURCES.

What Are the Properties of Conventional Water Heaters? Gas, Oil, Electric Water Heaters

Whether heated by gas, propane, oil or electricity, all conventional water heaters work the same way. Cold water enters the tank, and heated water leaves the tank. The heated water temperature is typically 120 to 140° F. When a fixture runs hot water, the heated water leaves the tank and cold water enters, triggering the thermostat and turning on the burner or element. If heated water flows out faster than the incoming cool water can be heated, we will run out of hot water. The larger the tank, the longer it takes to run out of hot water.

Water Heater Details (C) Carson Dunlop Associates Water Heater Details (C) Carson Dunlop Associates

- Courtesy Carson Dunlop Associates, used with permission

How Big Should My Water Heater Be - What Size?

Water heater details (C) Carson Dunlop Associates

Water heaters should be big enough to satisfy the needs of the house. A family of four will often find a 30-gallon gas or oil system or a 40-gallon electric system satisfactory.

Electric water heater drawing (left) courtesy Carson Dunlop Associates, used with permission

Details about water heater properties, recovery rates, sizes, are in articles listed beginning at WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER PROPERTIES
 

If you do not have enough hot water quantity, that is if you run out of hot water, or the hot water is not hot enough, see these diagnosis and repair articles:

HOT WATER IMPROVEMENTS - how to get more or hotter hot water in buildings
HOT WATER DELIVERY SPEED UP
- how to get hot water faster
HOT WATER PRESSURE EXPANSION RATE
- how much does water expand when heated, what are the safety concerns with hot water expansion?
HOT WATER PRESSURE LOSS
- how to diagnose and cure reduced or too weak hot water pressure or flow rate
HOT WATER QUANTITY IMPROVEMENT
- not enough hot water quantity? Read these articles

What is Water Heater Recovery Rate?

Water heater details (C) Carson Dunlop Associates

When the hot water is depleted, that is, when you are running hot water long enough that you run out of hot water, the recovery rate becomes important.

Water heater recovery rate drawing (left) courtesy Carson Dunlop Associates, used with permission

Generally speaking, oil fired hot water heating has the fastest rate of recovery, with gas fired water heaters and electric water heaters third. If water is drawn off slowly, the recovery rate may be such that the tank can be kept filled with hot water.

Faster water heater recovery rates allow more water to be drawn off without running out of hot water.

Should I Insulate My Water Heater?

Modern water heater tanks are insulated to slow the heat loss from the tank. Energy-efficient tanks have better insulation. Some people also insulate their hot water piping. But you should not add water heater insulation yourself without first reading the installation manual for your water heater. You may make the water heater unsafe and/or you may void the water heater warranty.

See Insulate Hot Water Piping and Insulate Hot Water Tank? for details

Water Heater Temperature Settings

Thermostats control the water temperature inside the water heater. There are some conflicting issues around appropriate water temperature. We don’t want the water so hot that it scalds people, but we want it hot enough to prevent bacteria like Legionnaires disease from growing in the water heater.

Also, dishwasher manufacturers often recommend that the water be 140° F, since some dishwashing detergents will not dissolve completely at lower temperatures. Many dishwashers have internal heaters to bring cooler water up to appropriate temperatures for washing dishes.

See WATER HEATER SAFETY for details.

Anti-Scald Valves and Mixing Valves at Water Heaters

Some jurisdictions require tempering valves on water heaters, so water in the tank is at 140°, but as it leaves the tank, cold water is mixed in to deliver 115° to 120° water. These tempering valves may be installed at the water heater, or at individual fixtures.

Details are at ANTI SCALD VALVES

List of Common Water Heater Problems

Not Enough Hot Water, or Water Not Hot Enough - what to do about it

This is the most frequent question people ask about hot water heating systems. See these detailed hot water diagnosis and repair or improvement articles:

HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER PRESSURE LOSS
HOT WATER QUANTITY IMPROVEMENT

Water Heater Fuel Problems: Oil, Gas, Electric

Malfunctioning burners, electric elements, sensors or controls will cause poor operation or may result in the system not working at all, meaning no hot water. See our separate articles on electric water heaters, gas water heaters, and oil fired water heaters for details. Also see the Home Reference Book Heating chapter for more information about fuel systems, burners and electric elements.

Water Heater Exhaust Venting Problems for gas or oil fired hot water heating systems

[Illustration: Vent Connector Length for a Water Heater]

To be safe and to work properly, most gas and oil water heaters have to be vented into a chimney with adequate draft. [An exception are electric water heaters and direct-vent water heaters.] Poorly arranged or disconnected vents are safety hazards, which should be corrected promptly.

Aluminum vents are not permitted. Vent sections should be as short as possible, screwed together, and should slope up 1/4 inch per foot, minimum. Vents should extend two feet above the roof and should be two feet above anything within ten feet horizontally. Vents should extend at least five feet above the draft hood. Exhaust gases spilling out at the draft hood or burner may present a life-threatening situation.

This problem requires immediate action. Some modern gas water heaters employ induced draft fans and high-temperature plastic venting that discharges out through the house wall. The vent materials were originally PVC, CPVC or ABS. In some areas these are replaced with special plastic vent pipes rated for the high exhaust gas temperatures.

Details are at GAS FIRED WATER HEATERS and at OIL FIRED WATER HEATERS

Water Heater Location

Gas or oil water heaters should not be in sleeping areas. This is a safety issue. Gas-fired heaters in garages should be 18 inches above floor level to reduce the risk of the heater igniting gasoline fumes, and should be protected from mechanical damage. Some jurisdictions call for electric heaters in garages to be similarly elevated.

Water Heater Noises

A snapping, hissing, crackling, or popping sound coming from the water heater tank when the heater is "on" may indicate a scale problem that is reducing hot water temperature, quantity, and water heater life. See WATER HEATER NOISES for details.

Why Bad Electric Water Heater Elements Mean Tepid Hot Water or Not Enough Hot Water or No Hot Water

It is not unusual to find one of the two elements in electric water heaters burned out. Replacing an element is not expensive. Most heaters are arranged so that both elements cannot be on at the same time – the elements operate in a sequence. Depending on which element fails, there may be some hot water, or none.

Details are at Electric Water Heater Element Tests and at Electric Water Heater Element Replacement Also see our complete article on electric water heater properites, inspection and diagnostic checklists, maintnance and repair procedures beginning at ELECTRIC WATER HEATERS

Water Heater Leaks & Leak damage

Water heaters can, of course, leak, and the tanks can be mechanically damaged.

Sludge in the Water Heater

Where sludge has accumulated in the bottom of the tank, water pressure from the hot water system may be limited. When water pressure problems are experienced on the hot water system only, it makes sense to drain the water heater to ensure that sludge accumulation is not the problem. Some experts recommend draining one or two gallons out of the bottom of the tank monthly to prevent sludge build-up.

Water Heater Relief Valve Safety Warnings

[Illustrations - TP Relief Valve and Gas Shutoff Valve]

The temperature/pressure relief (TP or TPR) valve lets water escape if the temperature or pressure is too high. This valve should be connected to a tube that discharges no more than six inches above floor level so hot water is not sprayed on to anyone nearby. Some areas require that the tube discharge outside the building.

The tube should be as large as the tank fitting and the tube end should never be threaded, capped or plugged. The tube diameter should be at least as large as the TPR valve fitting. The tube should be able to withstand 250°F temperatures, should have no shut-off valve, and should be as short and as straight as possible. An alternative to the high temperature function of the relief valve is a high temperature shutoff in the tank.

See RELIEF VALVES - Water Heaters for details.

Water Heater Age: When is the Water Heater Near End of Life?

Typical water heater life expectancy is 10-12 years, though there are exceptions with heaters that last a shorter period and others that we sometimes find last much longer. The life that your water heater manufacturer expects for the unit is reflected in the water heater warranty period.

Details are at Water Heater Life Expectancy Comparisons

Water Heater Maintenance Procedures

Proper water heater maintenance - such as draining sludge out of the tank or removing lime and scale can significantly increase water heater life. See these water heater maintenance articles:

  • To drain your water heater tank, for example to replace a part, see WATER HEATER DRAIN PROCEDURE.
  • To flush accumulated crud or debris from a water heater (yearly maintenance) see WATER HEATER FLUSH PROCEDURE
  • To de-scale or de-lime your hot water heater, see WATER HEATER SCALE - De-Liming Procedure
  • To diagnose and repair a bad water heater dip tube or anode, see WATER HEATER ANODES, DIP TUBES
  • To diagnose particulate debris in the building water supply, faucet strainers, etc. that comes from the hot water tank, and how to fix that problem, see WATER HEATER DEBRIS FLUSH

Tankless Water Heaters: Properties of, Common Problems With

As the name suggests, tankless water heaters have no storage capacity. Tankless heaters are typically gas or propane fired and have a burner, heat exchanger, venting system, and controls.

When the faucets and fixtures in the home are idle, the water heater is dormant. When there is a call for hot water, the heater detects the water flow and ignites the burners.

These powerful burners quickly heat the water inside the small heat exchanger. As hot water leaves, fresh cold water is drawn in and heated as it passes through. An advantage of this system is that you can’t empty all of the hot water out of the tank because there is no tank – just continuous hot water.

Details about tankless water heaters are found at TANKLESS WATER HEATERS. Tankless water heater basics are given just below.

Tankless Water Heaters do not "Store Hot Water"

The other major advantage over conventional water heaters is energy savings. Tankless water Water heaters have no reservoir of hot water sitting idle. It takes energy to keep the tank of water hot all the time for when it’s needed.

Small Size of Tankless Heaters

Tankless water heaters are much smaller than conventional heaters with storage tanks, and are usually wall-mounted. They do not take up much space.

Tankless water hater fuel and combustion gas venting

Most tankless water heaters are fuelled by natural gas or propane and are vented through a side wall of the house.

Efficiency of Tankless Water Heaters

Tankless water heaters are often more efficient than conventional water heaters, using modulating burners, direct venting and/or condensing combustion systems.

Mixing Valves on Tankless Water Heaters - Anti Scald Devices

Most systems include a mixing (tempering) valve and a means of setting a maximum water temperature to avoid scalding. This tempering valve mixes some cold water with the hot water leaving the unit to reduce the temperature.

Remote Controls on Tankless Water Heaters

Some tankless systems include a remote control, which can be used to monitor the performance of the system, display error codes or change the desired water temperature.

Other Uses of Tankless Water Heaters

Tankless water heaters may also be used to heat the home, either as part of a forced air combination system, or a radiant hot water system.

Watch out: The duty cycle of a conventional water heater or even a tankless water heater may not support home heating applications. See WATER HEATERS for HOME HEATING USE? for some warnings about using water heaters for conventional heating.

Common Tankless Water Heater Problems

Fuel Supply Troubles

The water heater must have a continuous fuel supply. Malfunctioning burners, sensors or controls will cause poor operation or may result in the system not working at all, meaning no hot water.

Scale Build-up

The small diameter of the heat exchangers means that these units are susceptible to clogging with scale, especially in areas with hard water. In hard water areas, annual de-scaling is recommended.

Longer Wait Times

When a hot water faucet is turned on, it may take longer to get hot water with a tankless heater than a conventional system. The delay between opening the faucet and getting hot water can be longer with tankless heaters than conventional tank heaters. Better tank locations and multiple tanks can help with issue.

Maximum Flow Rate for Tankless Water Heaters

The hot water flow rate is not only dependent on the heating capacity of the water heater and the output water temperature, but also on the inlet water temperature. Homes in northern climates draw water from colder sources, and since it takes longer to heat up colder water, tankless water heaters installed in these homes have lower hot water flow rates.

Minimum Flow Rate for Tankless Water Heaters

The burners are triggered by sensors that detect the flow of water. If the flow rate is less than 1/2 gallon per minute, the burners may not turn on and no hot water will be delivered. Water-saving shower heads, for example, may not flow enough to turn the water heater on, especially if the water heater needs a high flow rate before it will come on.

Tankless Water Heater Temperature & Pressure Safety Relief Valves

The temperature/pressure relief (TPR) valve lets water escape if the temperature or pressure is too high. This valve should be connected to a tube that discharges no more than six inches above floor level so hot water won’t scald anyone nearby. Some codes require that the tube discharge outside the building. The tube should be as large as the tank fitting and the tube end should never be threaded, capped or plugged. The tube should be able to withstand 250°F temperatures, should have no shut-off valve, and should be as short and as straight as possible.

High Cost for Tankless Water Heaters

Tankless water heaters are considerably more expensive than conventional tank-type heaters, and although tankless units are more energy efficient, it may take a long time to recover the extra investment.

High Maintenance for Tankless Water Heaters

Conventional water heaters are relatively inexpensive due to their simplicity. Tankless water heaters are more expensive and more complex. Their complexity also means that maintenance and repairs can be more expensive. Isolating valves help simplify draining and other regular maintenance.

Dirty Water Filter on Tankless Water Heaters

If the heater is equipped with a water filter, this should be checked and cleaned monthly, or performance will suffer.

Details about Tankless Water Heaters

See our article series on tankless water heaters or instant water heaters, point of use water heaters, and demand water heaters beginning at TANKLESS WATER HEATERS

- Adapted from the Home Reference Book, Carson Dunlop Associates.


Frequently Asked Questions (FAQs) about hot water heaters: how to buy, install, troubleshoot & repair water heaters

Question: is it more efficient to turn on the electric water heater just when needed?

I have been arguing with a landlord who believes it is more efficient to turn on the electric hot water heater to get the water to temperature then shut it off until it is necessary to heat it up again. It is possible with this small apartment water tank to have a few showers and wash dishes without the water getting too cold but l argue it is more efficient to leave it on and use less electricity to MAINTAIN the water temperature that to shut it off and have to reheat the whole water tank from cold to hot.
Who is correct? - Thanks - Dave 5/20/11

Reply: it depends ...

I'm afraid that the answer to the efficiency of turning off a water heater is ... it depends. Indeed it is common practice to install a timer on electric water heater systems to turn off the heater during long periods when it is not needed - a step that is reported to cut water heater operating costs

In my OPINION, for a building where hot water is in use at normal frequencies, people run hot water periodically during the day: morning bathing, dishwashing, hand washing, and evening bathing. In those cases it is certainly more convenient and functional to leave the water heater on. And the standby losses from a water heater that is in frequent use are low with modern insulated units.

For a building where hot water use is intermittent, with days or longer between use, there will usually be a savings from turning the water heater off, though there is the inconvenience of waiting for it to re-heat when occupants re-enter the building.

A common approach to economizing on electric water heater operating costs is the installation of a timer that turns the heater on and off at times to assure that hot water will be available when the occupants need it (and in order to comply with common rental agreement contracts that require the landlord to provide functional utilities).

Other Steps to Save on Electric Water Heater Operating Costs

Besides installing a timer on the electric water heater you can

- install heat traps on the plumbing lines atop the water heater to stop hot water from rising out of the water heater by convection when no one is actually running hot water in the building

- lower the water heater set temperature so that water is not heated more than needed and also so that there is no scalding risk

- install mixing valves at the heater or fixtures

Watch out: we do NOT recommend adding insulation to the water heater tank to try to safe energy even though some other websites make that suggestion. Modern water heaters are insulated by the manufacturer. Adding insulation can void a heater warranty and worse, if improperly installed (such as covering or blocking a pressure/temperature relief valve) it can be dangerous. Do not add insulation to a water heater without first checking with its manufacturer.

Question: smelly foamy hot water coming from Triangle Tube Indirect Water Heater: antifreeze leaks into the system?

I woke up one morning to foamy and smelly hot water. I called my heating and a/c guy and he told me my TT TR45 was releasing antifreeze into my hot water. The HWH was only 9 yrs old and still under warranty but the company wanted the unit back to check what happened (they would not admit their product was faulty). My plumber was sure the HWH was the problem and we replaced with a new Triangle Tube model (they no longer make TR45....wonder why...) since we were sure it would be covered under warranty. Now, Triangle Tube said the chamber had collapsed and it was not their product's fault but ours!! They said the outside pressure (from the boiler) made the chamber collapse. I'm so mad at them!! We did NOTHING new or different to make the pressure change! I wouldn't even know what to do to make the pressure change!

I was wondering if anyone here knows what could have made this happen that Triangle Tube is trying to cover up. Please help!
Thank you in advance! - Annette 3/9/12

Reply:

Annette,

You're describing a Triangle Tube brand indirect water heater. In these systems water from a heating boiler circulates in a heat-exchanging coil placed in the water heater tank.

I'd like to see more details about what the manufacturer has said and diagnosed about your warranty claim. A residential heating boiler normally operates at pressures under 30 psi; if pressures from the boiler, say in the zone heating your water heater, were higher than that, the pressure/temperature relief valve on the boiler should have opened to relieve the unsafe pressure, and you ought to have seen evidence of that discharge from the relief valve on your heating boiler.

There are things that can cause abnormally high heating boiler pressure. You should check the pressure readings on your heating boiler gauge, or have a service tech do so with an accurate independent gauge, just to be sure we don't have a double fault - an overpressure in the boiler and a relief valve that is not opening - that would be a very dangerous situation.

If you rule out abnormal boiler pressure, and if I understand that by "collapse" you mean that the water heater manufacturer says boiler pressure blew out their coil inside the heater, then at least so-far, things just are not adding up.

Perhaps you can ask the heater company to give a clear explanation of what they believe happened - in writing - so that we can understand the situation better. After all, as you'd point out to them, if there is something in the rest of your heating system that is improper it needs to be properly understood so that it can be properly repaired.

Reader follow-up:

Thank you so much for your reply. Here's a little more info....and, yes, it is a TT indirect water heater.
TT was saying that the inner chamber collapsed due to external high pressure. We had fully working pressure valves on both the boiler and the HWH. When the HWH was removed, it was full. There was no water on the floor and nothing had collapsed. Upon removal and the "abuse" of moving the heavy thing outside, my contractor said that the HWH released water in the driveway (he believes that was when it collapsed).
I asked the TT company to give me a full explanation and I even suggested they send a rep here to check out the boiler room. So far, I have not heard from them.
In your opinion, what could have caused the HWH to malfunction?
Thanks again!

Question: un-vented electric water heater leaks

I have an unvented electric water heater(EWH) which is supplied by a flow pump. A few minutes after it starts to heat up the water, the relief valve starts leaking. The EWH and valve are newly installed. How do I solve the problem. I suspect that the valve is cheap version set to low pressure. - Dave 8/13/2012

Reply:

Dave,

Indeed an electric water heater does not need a flue, vent, nor chimney.

Watch out: But a leaky relief valve is dangerous either because the system is at too-high a pressure (see BLEVE EXPLOSIONS) or because a valve that is leaking for its own reasons (bad washer, dirt on the valve seat) can become clogged by mineral deposits and then fail to operate when it should in an emergency.

Most water heater pressure/temperature relief valves are not adjustable and are factory-set at a prescribed relief pressure (such as 150 psi), though we've seen some older TP valves on electric heaters that indeed could be adjusted.

Details on how to diagnose and fix this problem are at RELIEF VALVE LEAKS.

Question: hot water is not evenly distributed in my house since a new water heater was installed

Hi,

The water heater was installed professionally and running smoothly since yesterday. After installation was done, it seems that the hot water is not enough distributed to all other areas of my house such as powder room and kitchen (1st level), master bath (in sinks only – 2nd level), except for in the shower stall where the hot water is not the problem. Also, just to let you know that before the installation, the old heater (Bradford White 50 gal, since 2000was leaking and that’s why was replaced) never had this kind of an issue. So, what do you thing is the problem now?

Thank you for your understanding,
Val 11/7/12

Reply:

Val,

Since your water heater is basically just that, a tank and heater, it should not directly have an effect on how water is distributed in the building - hot water leaves the water heater without knowing where it's headed.

But other things might explain your hot water distribution complaint.

A new, lower water temperature setting might make more distant fixtures run cooler at first use

A valve left partly closed would reduce flow rate downstream from the valve, as can some more subtle problems like a supply line partly blocked by debris or a solder blob, or by mineral deposits from hard water.

Question: cement water tank and hot water taps give off a fishy odor

We have recently moved to a house with a cement water tank all hot water taps give off a strong fishy odour the cold does not - Carolyn 11/24/12

Reply:

Carolyn

I'm not sure what the cement water tank is or what it has to do with your hot water supply.

See HYDROGEN SULFIDE GAS. The odor source in a water heater is often found to be a contaminated hot water tank (bacteria) or a bad water heater tank anode (ANODES & DIP TUBES on WATER HEATERS).

...

Ask a Question or Search InspectApedia

Questions & answers or comments about diagnosing & repairing hot water heaters.

Ask a Question or Enter Search Terms in the InspectApedia search box just below.

Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

  • Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
  • John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
  • Carson, Dunlop &
Associates Ltd., TorontoCarson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
    • Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
    • Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
    • Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
      Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
    • The Home Reference Book, a reference & inspection report product for building owners & inspectors.
      Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
    • The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
      Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
    • The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
      Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
    • The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
  • Thanks to Scott C. LeMarr, for sharing his file of keys to decode Furnace and Water Heater Age from the data provided on the manufacturer's equipment labels. Mr. LeMarr is a professional home inspector, Certified Professional Inspector/President, MASTER Indoor Environmental Specialist (MIES). Vice President of Wisconsin NACHI. He and his company, Honest Home Inspections, LLC. can be reached at 262-424-5587 or by email to scott@honesthomeinspections.com
  • "Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
    • "Heat Exchangers for Solar Water Heating Systems", U.S. DOE describes the types of solar water heater heat exchange methods between the sun and the building's hot water supply
    • "Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
    • "Solar Water Heating System Maintenance and Repair", U.S. DOE
    • "Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
    • "Scaling and Corrosion in Solar Water Heating Systems", U.S. DOE
    • www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these article
  • "Building Owner Water Heater Safety Notice", Building Department, City of Colleyville TX, web search 09/24/2010, original source: http://www.colleyville.com/dmdocuments/Building%20
    Owner%20Water%20Heater%20Safety%20Notice%203-6-102.pdf
    Quoting:
    Water heater safety is imperative to the occupants of a building or structure. If improperly installed, water heaters can be detrimental to the structure, as well as being potentially fatal to its occupants. The proper installation of a water heater is so important that according to Texas State Law all water heater installations must be inspected by a state licensed plumbing inspector.
  • "Scale formation in water heaters and methods of prevention", Krappe, Justus Maximilian, Engineering experiment station. Gas engineering bulletin; no. 6; Research series; no. 74; On cover: Engineering bulletin, Purdue university. Vol. xxiv, no. 3a. June, 1940 (Layfayette Indiana) commonly referred to in some references as "Purdue University Bulletin No. 74" - thanks to researcher Robyn Goldstein for the full citation. LCCN: 40028844 & OCLC: 1038544 - Water analysis, water softening, hot-water supply. 27pages. You can obtain this document through your local library. (full copy file at InspectAPedia 3/31/2010) Purdue B074 can be hard to locate online.
    Also Bradford White Corporation (a manufacturer of water heaters) has published excerpts from that document, available at Purdue_B074_BradfordW.pdf

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
  • Home Reference Book - Carson DunlopThe Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

    Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
  • Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
    Special Offer
    : Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.

  • Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
  • National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
  • "Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
  • ...

HOME ABOUT CONTACT COPYING DESCRIPTION POLICIES PRINTING PRIVACY © 2013 Copyright InspectAPedia.com