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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
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 HeatersPlease 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 What Are the Properties of Conventional Water Heaters? Gas, Oil, Electric Water HeatersWhether 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.
- Courtesy Carson Dunlop Associates, used with permission How Big Should My Water Heater Be - What Size?
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 What is Water Heater Recovery Rate?
Water Heater Temperature SettingsThermostats 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 HeatersSome 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 ProblemsNot Enough Hot Water, or Water Not Hot Enough - what to do about itThis 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 Water Heater Fuel Problems: Oil, Gas, ElectricMalfunctioning 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 LocationGas 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 NoisesA 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 WaterIt 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 damageWater heaters can, of course, leak, and the tanks can be mechanically damaged. Sludge in the Water HeaterWhere 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 ProceduresProper 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:
Tankless Water Heaters: Properties of, Common Problems WithAs 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 HeatersTankless 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 ventingMost tankless water heaters are fuelled by natural gas or propane and are vented through a side wall of the house. Efficiency of Tankless Water HeatersTankless 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 DevicesMost 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 HeatersSome 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 HeatersTankless 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 ProblemsFuel Supply TroublesThe 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-upThe 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 TimesWhen 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 HeatersThe 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 HeatersThe 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 ValvesThe 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 HeatersTankless 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 HeatersConventional 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 HeatersIf the heater is equipped with a water filter, this should be checked and cleaned monthly, or performance will suffer. Details about Tankless Water HeatersSee 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 heatersQuestion: 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. 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 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! Reply:Annette, 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. Question: un-vented electric water heater leaksI 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 installedHi, Reply:Val, A new, lower water temperature setting might make more distant fixtures run cooler at first use Question: cement water tank and hot water taps give off a fishy odorWe 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. ... Ask a Question or Search InspectApediaQuestions & 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 & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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Carson, Dunlop & Associates Ltd.,
The Home Reference Book - the Encyclopedia of Homes