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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
ANTI SCALD VALVES
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions

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

ENERGY SAVINGS in buildings

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 FIRED WATER HEATERS

PIPING IN buildings, Clogs Leaks Types
PLASTIC HEATER VENT

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

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

TANKLESS COILS
  AQUASTAT CONTROL Functions
  Clogged Pipes / Tankless Coil De-Scale
  MIXING / ANTI-SCALD VALVES
  Tankless Coil Conversions
  Tankless Coil Leaks
  Tankless Coil Hot Water Increase

TANKLESS WATER HEATERS
  Electric Shower Heaters
  Guide to Tankless Water Heaters
  Operation & Characteristics
  Problems & Defects
  Hot Water Delivery Speedup
  Installation Requirements & Costs
  Should I Convert to a Tankless Heater?
  Calculate Water Heater Requirements
  Capacities of Tankless Water Heaters
  Life Expectancy & Applications

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 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 REPAIR GUIDE - WELLS
WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER PUMPS & WELLS
WATER PURIFIERS
WATER QUALITY TESTS, CONTAMINANTS, TREATMENT
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING

More Information

Warning about improper relief valve installation at a water heater (C) Carson Dunlop Guide to Hot Water Heater Safety Features & Water Heater Safety Inspections
InspectAPedia®  -      

  • Checklist of water heater safety inspection points
  • Authorities recommending water heater safety inspections
  • How to compare various safety features of hot water heating methods: electric, gas, high efficiency gas, oil, high efficiency oil, solar, tankless coils, etc.
  • Questions & answers about safety inspections for water heaters

This article discusses the need and procedure for regular safety inspections of water heating equipment. We list authoritative citations supporting the need for water heater safety checks. Included are 31 water heater safety checklist items.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Domestic Hot Water Heater Safety Inspection Recommendations

Authorities recommend a periodic safety inspection of all water heating equipment, including all types of water heaters. (We list and compare different types of water heating systems at WATER HEATER PROPERTIES.) Thanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article. CONTACT us to suggest additional codes, authorities, or water heater safety inspection procedures.

Potential Water Heater Safety Hazards and Other Water Heater Inspection Points That Should be Inspected or Checked

Except for our having placed two very common water heater safety concerns - scalding and relief valve problems - at the top of this list, the rest of our water heater safety inspection list is arranged alphabetically and includes links to more details about each item.

  1. Hot Water Scalding Burn Hazards: water heater temperatures may be set too high, risking serious or even fatal scalding hot water burns to building occupants. Details are at ANTI SCALD VALVES.

    Watch out for hot water scalding hazards and unsafe water tank or calorifier pressures: By the way, typical safe temperatures in water heaters or calorifiers used for washing and bathing are around 104 degF up to a max (and risk of scalding) of 120 degF, or from at about 40-49 °C.

    Temperature settings: on the water heater
    , setting the temperature very high in an attempt to obtain more hot water can be dangerous and lead to serious scalding burns for the building's occupants unless water tempering or mixing valves or other temperature safety controls are provided and properly set at the plumbing fixtures.

    At a temperature setting of 100 degF or below most water heaters are unlikely to scald an occupant; more than 5 minutes exposure at 120 degF are required to produce 2nd & 3rd degree burns on adult skin.

    Hot Water Scalding Burn Warning: MIXING / ANTI-SCALD VALVES contains a table of hot water temperatures which are safe and which explains the risk of second and third degree scalding burns that occur at different water temperatures and exposure times. Also see Anti-Scald Valves & Hot Water Quantity.

  2. Unsafe Water Heater Pressure/Temperature Relief Valves: Water heaters [and any pressurized tank] require a pressure [and on heaters, temperature] safety relief valve or TP valve as well as an extension or discharge tube. Missing, modified, improper version, improper discharge tube piping. See details at Relief Valves - Water Heaters where we also discuss procedures for testing water heater pressure/temperature relief vales. Additional information about pressure and temperature relief valves is found at RELIEF VALVES - TP Valves on Boilers.
    Warning about improper relief valve installation at a water heater (C) Carson Dunlop
    Proper relief valve location: In Carson Dunlop's sketch at left the pressure relief valve is improperly installed on the far side of the pressure reducing valve at the water heater. This is a very dangerous installation.

    In some locations where hard water is found, an expansion control valve is also used to drain excess hot water tank pressure. But these separate water system expansion control valves, discussed below and also at RELIEF VALVES - Water Heaters, may indeed be located away from the water heater.

    BLEVE explosions
    or boiling liquid vapor explosions
    can occur at both domestic water heaters (calorifiers or geysers) and at hot water heating boilers (hydronic heating systems). We discuss the role of pressure/temperature relief valves in protecting against these hazards at RELIEF VALVES - TP Valves on Boilers and at RELIEF VALVES - Water Heaters.

    Information from the Colleyville Building Dept.
    Improperly installed safety devices: If the temperature and pressure relief valve (T&P-valve) and similar safety devices (e.g. expansion tank) are not properly installed the result can be deadly. The T&P-valve is designed to prevent a water heater tank from exploding if temperatures and/or pressures exceed their safe operating limits. There are many documented cases where water heaters have malfunctioned with catastrophic results leading not only to property damage but to loss of life as well. Exploding water heaters have been described as bombs exploding.
  3. Chimneys, vents, and flues to avoid fire or flue gas spillage: for gas or oil fired water heaters the flue vent connector, draft hood or barometric damper, and chimney must be safe to avoid fire and potentially dangerous carbon monoxide hazards. See CHIMNEY INSPECTION DIAGNOSIS REPAIR.
    Also note this information from the Colleyville Building Dept.
    Improperly installed venting system: If improperly installed, the water heater venting system may fail to function properly. The result of that failure can be deadly. If the venting system is installed incorrectly it could disconnect and leak carbon monoxide into your home. Carbon monoxide (CO) is a colorless, odorless, extremely poisonous gas formed by incomplete combustion of carbon or carbonaceous material; also referred to as the silent killer.
    Also see PLASTIC HEATER VENT.
  4. Combustion gas venting for water heaters: any fossil fuel fired water heater (oil or gas fired) requires safe venting of the combustion products, through a chimney or in the case of high efficiency heaters, through a plastic vent line. Watch out: venting a small gas fired water heater through a large old masonry chimney may be unsafe. See CHIMNEYS for details. The presence of soot around gas fired flues or vents is an indication of a dangerous condition. See CARBON MONOXIDE - CO. Also see SOOT on OIL FIRED HEATING EQUIPMENT.
    Information from the Colleyville Building Dept. is below:

    Water heater installed in a closet or confined space: If your water heater is installed in a closet or confined space it is required to have the appropriately sized upper and lower combustion air openings. If a gas appliance such as a water heater is not provided with the appropriate amount of combustion air it will malfunction. Typically what will happen is the gas burner will be starved for oxygen and the burner flame will go from a short blue flame to a large yellow flame causing the flame to escape the combustion chamber possibly (most likely) causing a fire.
  5. Clearance to combustibles: fire safe clearance between flue vent connectors or chimneys and combustibles is required, typically 1" for "zero clearance" metal flues, up to 18" for flue vent connectors serving oil fired heating equipment. See
    FIRE CLEARANCES INDOORS
    Fire Clearances for Masonry Chimneys
    Fire Clearances for Metal Chimneys
    FIRE CLEARANCES, Single-Wall Metal Flues
    Fire Clearance Wood & Coal Stove Flues
      Chimney Height & Clearance
      Reduction in Fire Clearance - Heat Shields
      Single Wall Metal Flues - Oil fired heaters
      Single Wall Metal Pipe Flues - Gas heaters
      Wood & Coal Stove Flues
      Fire Clearance Safety Hazards, other

    Information from Village of Mt. Prospect,
    Proper clearances to storage must be provided around fuel burning appliances. See manufacturers instruction for exact clearance (typically a minimum of 18 inches). [refers to oil fired heating equipment].
  6. Combustion air: any fossil fuel fired water heater (oil or gas fired) requires combustion air. The volume of air intake to the utility room where the heater is installed depends on the BTUs of the device and the type of fuel. Watch out: installing a gas or oil fired heater in a small confined space whose door is shut and which lacks adequate combustion air is unsafe. See details at COMBUSTION AIR DEFECTS, and at COMBUSTION AIR for TIGHT buildings. More information is at COMBUSTION GASES & PARTICLE HAZARDS and at COMBUSTION PRODUCTS & IAQ.
  7. Damage protection for water heaters: Also referred to in some communities as "bollard or barrier" to protect the water heater, water heaters in garages should be protected from mechanical damage such as being struck by an auto
  8. Earthquake Strapping for water heaters: required in earthquake zones, water heaters must be secured against independent movement to reduce the chance of fire in the event of an earthquake
  9. Electric wiring and overcurrent protection for electric water heaters: proper wiring size, connections, overcurrent protection and grounding are important for electrical safety. Also a visual inspection of the electric water heater's thermostats can often detect signs of failure or overheating at those components.
    Information from the Colleyville Building Dept.
    Improperly installed electrical wiring: If your water heater is powered by electricity the electrical circuit may not be correctly sized to accommodate the minimum required amperage draw to the water heater replacement. This can lead to electrical inefficiencies and may cause a fire or damage electrical equipment.
  10. Elevating stand for water heater: required by some building codes that specify that the water heater must be elevated above floor level, for example for water heaters installed in a garage. Note that many new water heaters are FVIR rated or "flammable vapor ignition resistant"
  11. Electric Water heater bottom insulating board: for electric water heaters in unheated spaces, the tank is placed on a non-compressible insulated surface with at least an R-10 insulation rating to reduce heat loss out of the bottom of the water heater tank (saving on operating cost).
  12. An Expansion Control Valve is used on water heaters in south and Western Australia where hard water is found, and in some other countries or other jurisdictions. The Expansion Control Valve discharges water into a drain to relieve excess pressure in the hot water tank. The purpose of this valve is to release pressure through a separate control so that the safety provided by the Temperature and Pressure Relief valve is not compromised by clogging from minerals should that valve frequently open.

    The expansion control valve should be tested every six months, following the same procedure as for temperature and pressure relief valves as we described above.

  13. Expansion Tanks for water heater systems: Expansion tanks are required in some areas when the customer is on a “closed” water system: when water is heated in a closed water system, thermal expansion can cause rapid increases and decreases in system pressure which can in turn cause spillage at pressure/temperature relief valves (and related building water, flood, or mold damage), or damage to other plumbing components. An expansion tank or additional pressure/temperature relief valves can prevent these problems and may also extend the life of the water heater.

    Question: should I adjust the pressure in my water heater expansion tank?

    The InspectAPedia site has plenty of information on setting pressures for well systems with a bladder, but I can't find anything relating to recommendations on how the small (1 and 2 gallon) water heater-type expansion safety tanks should be pressurized. The manufacturer typically ships these with 40 psi--is that good for all conditions, or should the tank be pressurized to average line pressure on a municipal system? For example, average pressure delivered to my residence by the city is 70 psi. So I'm wondering what normal practice is--leave the tank at the pressure as the manufacturer shipped it, or pressurize to average incoming water line pressure when one is on a municipal system? - W.F.

    Reply: select the correct water heater expansion tank size, then leave the factory expansion tank set where found at 40 psi under normal circumstances, and never exceed 80 psi.

    Watch out: We agree that it's important to get the size and pre-charge pressure of a water heater expansion tank right, as while the tank is preventing inappropriate relief valve overpressure spillage under normal water heating conditions, the expansion tank also needs to allow the relief valve to spill if an unsafe temperature or pressure occurs at the water heater. (See BLEVE EXPLOSIONS) .

    The correct size (and pressure) for an expansion tank used on a domestic water heater (potable water or hot water tank) is determined based on the incoming water supply pressure, the water heater tank size, and the spill pressure set on the water heater tank's pressure/temperature relief valve.

    Watts® offers some guidance at http://www.watts.com/pages/learnAbout/thermalExpansion.asp?catId=64 and at
    http://www.watts.com/pages/support/sizing_DET.asp Watts® offers an expansion tank size calculator. Or you can check the product specifications for water heater expansion tanks such as at http://media.wattswater.com/ES-PLT.pdf.

    There you'll see a table that matches water heater size and water supply pressure to expansion tank SIZE. If you pick the proper expansion tank size, using it at the factory pre-charged pressure should be exactly correct.

    For your example and using the sizing table, a Watts® expansion tank type "A" (PLT-5 or 2.1 gallons) would work for a supply pressure up to 70 PSI IF your water heater tank is no larger than 50 gallons. If your water heater tank is 80 or 100 gallons you'd need a PLT-12 (4.5 gallons), and a 120 gallon tank would need a PLT-20 (8.5 gallons) - all at 70 psi incoming water pressure and all with the factory pre-charge expansion tank pressure of 40 psi.

    Older Watts "DET" expansion tanks are obsolete but may still be in use on some water heaters. Currently the company sells hot water expansion tanks in models PLT-5 (2.1 gallons), PLT-12 (4.5 gallons), PLT-20 (8.5 gallons), and PLT-35 (14-gallons) sizes. Other manufacturers offer similar sizes and models. Quoting from Watts: [http://www.watts.com/pages/_products_details.asp?pid=852]

    Series PLT Potable Water Expansion Tanks are designed to absorb the increased volume of water created by thermal expansion and to maintain balanced pressure throughout the potable water supply system. Series PLT tanks feature a pre-pressurized steel tank with an expansion membrane that prevents contact of the water with the air in the tank. This prevents loss of air to the water and ensures long and trouble-free life for the system. These tanks may be used with all types of Direct Fired Hot Water Heaters (gas, oil or electric) and hot water storage tanks. IAPMO listed and ANSI/NSF 61 certified. Maximum Pressure: 150psi (10 bar).

    Series PLT Potable Water Expansion Tanks are designed to absorb the increased volume of water created by thermal expansion and to maintain balanced pressure throughout the potable water supply system. Heated water expands, and in a domestic hot water system, the system may be closed when the potable water system is isolated from the public water supply by a one-way valve such as pressure reducing valve, backflow preventer or check valve. Provisions must be made for this expansion. Series PLT expansion tanks absorb the increased volume of water created when the hot water storage tank is heated and keeps the system pressure below the relief setting of the T&P relief valve. It is a pre-pressurized steel tank with an expansion membrane that prevents contact of the water with the air in the tank. This prevents loss of air to the water and insures long and trouble free life for the system. These tanks may be used with all types of Direct Fired Hot Water Heaters (gas, oil or electric) and hot water storage tanks.


    Details on how much water expands when it is heated are found at HOT WATER PRESSURE EXPANSION RATE.
  14. Flame shields: Gas or oil fired water heaters include a flame shield around the port used to inspect the burner - it must remain in place and be undamaged. Look for signs of flame spillage or roll-out at gas fired water heaters.
  15. Gas shutoff valves: Gas fired water heaters in some jurisdictions require an automatic gas shutoff valve that responds to high water heater temperature. See details at Gas Shutoff Valves.
  16. Gas piping and gas piping drip leg: Gas piping must be correctly installed, using the proper piping materials, connections, shutoff valves, and must not be leaking. The drip leg also referred to as a "dirt leg", the drip leg is required by some water manufacturers to collect moisture (rare in modern fuel gases) or dirt to keep these harmful materials out of the water heater gas burner. See details at Gas Piping Defects. Also see Gas Leak Detection.
    From the Colleyville Building Dept.
    Improperly installed gas piping: If the gas-supply piping connected to your water heater is incorrectly sized the gas system’s ability to properly supply the necessary gas demand to your water heater may be compromised. This could potentially create energy inefficiencies and lead to a gas burner malfunction or incomplete combustion of the fuel gas which could ultimately cause a fire or a carbon monoxide leak.
  17. Home heating using a water heater: may be taxing the equipment beyond its intended use. See
    WATER HEATERS for HOME HEATING USE?
  18. Indirect fired water heaters: use heat from an independent source such as a separate gas or oil fired heating boiler or solar heating system to heat water in the hot water tank. But these tanks also require temperature/pressure relief valve, safe plumbing, and scald protection. See INDIRECT FIRED WATER HEATERS
  19. Insulation: as an add-on extra water heater tank insulation is not generally recommended by water heater manufacturers. If insulation is improperly installed on a water heater it may make the system very unsafe, including blocking the draft hood on a gas fired water heater (a carbon monoxide hazard) or blocking a relief valve preventing safe pressure/temperature relief valve operation. See Insulate Hot Water Tank?.
  20. Leak pan and drain: for water heaters installed on a wood floor without a drain, in an attic or ceiling where water damage from a leaking tank can damage the building, possibly causing a costly mold contamination, insect attack, or structural rot.
  21. Leaks in water heaters: leaks in the water heater tank body mean the heater needs to be replaced, and also that it may be unsafe.
  22. Mobile home water heater safety: see MOBILE HOME WATER HEATER DEFECTS
  23. Noises: noises in the water heater may indicate that an excessive lime or scale buildup has occurred, possibly increasing water heating costs, reducing the quantity of hot water available, and in some circumstances, it may affect the safety and life of the water heater tank. Details are at NOISES COMING FROM WATER HEATER.
  24. Odors: such as a "rotten egg" smell or sewer gas smells may be due to a bacterial contamination in the heater tank or due to a deteriorated sacrificial anode (ANODES & DIP TUBES on WATER HEATERS), or it may be due to contaminants in the water supply. See ODORS IN WATER and see SEWER GAS ODORS
  25. Oil burner noises, smoke, odors and on occasion soot on and around an oil fired water heater indicate improper operation of the equipment and risk a puffback or other potential safety hazards. See OIL BURNER NOISE SMOKE ODORS.
  26. Oil shutoff valves: oil fired water heaters should always have their own oil safety valve: a special valve installed on the oil line near the water heater and which will automatically close and stop the flow of oil to the water heater should a fire occur. Watch out: often in a building where there is an oil fired heating system as well as an oil fired water heater, the installer may have installed the safety valve only at the oil tank or only at the heating boiler or furnace. See details at OIL LINE SAFETY VALVES.
  27. Spill switch on gas flues: Gas fired water heaters should have a flue gas spillage switch that shuts off the gas valve if needed. See details at Spill Switches.
  28. Tankless coils used for producing domestic hot water can present a special scalding risk. See ANTI SCALD VALVES and see TANKLESS COILS.
  29. A Temperature Limiting Valve that limits the outgoing water temperature to 50 degC in order to prevent scalding is installed on water heaters in some locations. This valve should be checked annually by measuring water temperature at a nearby water taps, making sure that the water delivered closest to the water heater is not hotter than 50 degC. See ANTI SCALD VALVES.
  30. Water pressure reducing valves / water pressure regulators: if the building water pressure gauge reading is ever found at 80 psi or higher, you will want to install a water pressure regulator at the point where water supply enters the building. If your building already has a water pressure gauge installed, it may be defective or it may be set too high. The articles listed just below discuss how to adjust a water pressure regulator:

    WATER PRESSURE REDUCER / REGULATOR
      What's a Water Pressure Regulator?
      WATER PRESSURE VARIATION CAUSES
      Diagnose Poor Municipal Water Pressure
      WATER PRESSURE REGULATOR ADJUSTMENT

  31. Working space: Water heaters require safe working space around the device regardless of the heater type

Building Authorities & Other Sources Recommending Water Heater Safety Inspections

  • Air-Conditioning, Heating, and Refrigeration Institute, http://www.ahrinet.org/Content/GAMAnetRedirect_920.aspx
  • "ANSI Z21.10.1-2009 CSA 4.1-2009 - Gas Water Heaters Volume I, Storage Water Heaters With Input Ratings Of 75,000 Btu Per Hour Or Less" American National Standards Institute, ANSI, web search 09/24/2010 original source: http://webstore.ansi.org/RecordDetail.aspx?sku=ANSI+Z21.10.1-2009+CSA+4.1-2009- Quoting:

    Applies to newly produced, automatic storage water heaters having input ratings of 75,000 Btu/hr (21 980 W) or less (see Part IV, Definitions), hereinafter referred to as water heaters or appliances, constructed entirely of new, unused parts and materials: For use with natural gas; for use with manufactured gas; for use with mixed gas; for use with liquefied petroleum gases; for use with LP gas-air mixtures; for recreational vehicle installation for use with liquefied petroleum gases only (see 1.2.25); for manufactured home (mobile home) installation convertible for use with natural gas and liquefied petroleum gases when provision is made for the simple conversion from one gas to the other (see 1.2.24); for recreational vehicle installation convertible for use with natural gas and liquefied petroleum gases when provision is made for the simple conversion from one gas to the other (see 1.2.25); and for use with combination potable water/space heating applications.
  • Building Owner Water Heater Safety Notice provided by the Colleyville TX building department. Quoting from that document:

    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.
  • Common Water Heater Codes, Fast Water Heater Company, web search 09/24/2010 original source: http://www.fastwaterheater.com/waterheatercodes.asp
    This source lists several water heater safety checkpoints, and asserts: Quoting:

    Due to various injuries and accidents related to water heaters over the last ten years, most cities and counties have adopted either the 2001, 2003 or 2006 Uniform Plumbing Code (or in the case of California, the California Plumbing Code).
  • Guide to Rental Property Maintenance Inspection, Village of Mount Prospect, 50 S. Emerson St., Mount Prospect, IL 847-818-5328, www.mountprospect.org, web search 09/25/2010, requires Annual, routine inspections of apartment buildings that are licensed by the Village, original source: http://www.mountprospect.org/services/community_
    development/envhealth/housing/prop_maint_insp_1209.pdf

Thanks to reader D.B. for discussing the need for water heater safety inspections, suggesting some of the water heater inspection requirement code sources above, and for suggesting the need for documenting sources of authority, building codes, water heater manufacturers, water heater operating and installation manuals, and other sources recommending inspection and safety practices involving water heaters (as well as other tanks and pressurized containers in buildings).

A Comparison of the Relative Safety of Different Types of Water heaters

Gas water heater with draft hood removed (C) Daniel Friedman

In the LP gas fired water heater shown in our photo, the installer had trouble fitting the draft hood atop the heater since there was then not enough overhead clearance to route the flue out of the building. The installer has thoughtfully left the draft hood he removed, an important safety device, sitting atop the water heater as a reminder that this is an improper installation.

There is just too much subjectivity to make a sensible answer to this question. Some people are frightened by the prospect of a natural or LP gas explosion in a building.

But while it's difficult to set heating oil on fire and so explosions based on the fuel character may be less likely than with an LP or natural gas system, an oil-fired water heater runs at much higher burner and exhaust flue temperatures and so can prevent other types of fire risk.

Most critical with any water heater are that the heater is properly installed and includes the required safety controls such as those responsible for limiting temperature and pressure. Any water heater should include a temperature and pressure relief valve installed of the proper type and at the correct location. Gas-fired devices also should include flue-gas spillage detectors. Oil-fired devices should also include a fire-safety valve that shuts off fuel to the appliance in case of fire.

We guess that proper installation, inspection, and maintenance make more difference in the safety of a water heater than the innate differences among heater types, fuels, etc.

List of Hot Water Heater Safety Devices and Features

  1. Pressure/Temperature Relief Valves: Water heaters (and any pressurized tank) require a pressure and temperature safety relief valve or TP valve as well as an extension or discharge tube. In Carson Dunlop's sketch at page top the pressure relief valve is improperly installed on the far side of the pressure reducing valve at the water heater. This is a very dangerous installation. See our Guide to Heating System Boiler Temperature and Pressure Relief Valves.
  2. Spill switch on gas flues: Gas fired water heaters should have a flue gas spillage switch that shuts off the gas valve if needed
  3. Gas shutoff valves: Gas fired water heaters in some jurisdictions require an automatic gas shutoff valve that responds to high water heater temperature.
  4. Oil shutoff valves: oil fired water heaters should always have their own oil safety valve: a special valve installed on the oil line near the water heater and which will automatically close and stop the flow of oil to the water heater should a fire occur. Watch out: often in a building where there is an oil fired heating system as well as an oil fired water heater, the installer may have installed the safety valve only at the oil tank or only at the heating boiler or furnace.
  5. Flame shields: Gas or oil fired water heaters include a flame shield around the port used to inspect the burner - it must remain in place.
  6. Combustion air: any fossil fuel fired water heater (oil or gas fired) requires combustion air. The volume of air intake to the utility room where the heater is installed depends on the BTUs of the device and the type of fuel. Watch out: installing a gas or oil fired heater in a small confined space whose door is shut and which lacks adequate combustion air is unsafe.
  7. Combustion gas venting by a chimney: any fossil fuel fired water heater (oil or gas fired) requires safe venting of the combustion products, through a chimney or in the case of high efficiency heaters, through a plastic vent line. Watch out: venting a small gas fired water heater through a large old masonry chimney may be unsafe. See CHIMNEYS for details.
  8. Temperature settings: on the water heater, setting the temperature very high in an attempt to obtain more hot water can be dangerous and lead to serious scalding burns for the building's occupants unless water tempering or mixing valves or other temperature safety controls are provided and properly set at the plumbing fixtures.

    At a temperature setting of 100 degF or below most water heaters are unlikely to scald an occupant; more than 5 minutes exposure at 120 degF are required to produce 2nd & 3rd degree burns on adult skin.

    Hot Water Scalding Burn Warning: MIXING / ANTI-SCALD VALVES contains a table of hot water temperatures which are safe and which explains the risk of second and third degree scalding burns that occur at different water temperatures and exposure times.
  9. Working space: Water heaters require safe working space around the device regardless of the heater type
  10. Damage protection: Water heaters in garages should be protected from mechanical damage such as being struck by an auto
  11. Water Heater Expansion Tanks: Expansion tanks are required in some areas when the customer is on what is called a “closed” water system. See our discussion of how and why, above.
  12. Regular safety inspections: Water heaters should be periodically inspected for safety and evidence of damage or leaks. An example of an unsafe water heater is one whose relief valve has been leaking, modified, or blocked, or a heater whose exhaust flue lacks proper fire clearance distances.

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BACKDRAFTING HEATING EQUIPMENT
BLEVE EXPLOSIONS

CARBON MONOXIDE - CO
CHIMNEY INSPECTION DIAGNOSIS REPAIR
DEBRIS in WATER SUPPLY, Water Heater

WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
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
MIXING / ANTI-SCALD VALVES

NOISE, WATER HEATER

ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
OIL FIRED WATER HEATERS

PLASTIC HEATER VENT

RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks

SAFETY, HEATING INSPECTION
SCALE REMOVAL, WATER HEATERS

  • Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
  • Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
  • A.O. Smith water heater safety sticker: 182734-000 Rev.00 observed on the gas fired water heater shown at High Efficiency Gas Water Heaters
  • "Building Owner Water Heater Safety Notice", Colleyville Building Inspection Department, 100 Main Street, Colleyville, Texas 76034. Tel: 817-503-1030 Website: www.colleyville.com, 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.
  • Thanks to reader Donald Bagley for discussing the need for water heater safety inspections, September 2010. Mr. Bagley performs facility inspections and works with the Maricopa County, AZ  Risk Management/Safety Division.  

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 Dunlop The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book 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. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
  • Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
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