Water heater safety - hot water cylinder safety:

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 33 water heater safety checklist items.

We include water heater clearance distances or spacing as well as other inspection points.

How to Inspect the Safety of Domestic Hot Water Heaters - 34 inspection points

Authorities recommend a periodic safety inspection of all water heating equipment, including all types of water heaters.

[Click to enlarge any image]

Our photo shows the results of a fire at an LP gas fired water heater installed outdoors in Gogorron, San Luis Potosi, Mexico.

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 - temperature controls:
   
   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 the temperature controls for each type of water heater, found in:
   
   ANTI_SCALD VALVES & HOT WATER QUANTITY
   
   ELECTRIC HOT WATER TEMPERATURE CONTROL
   
   ELECTRIC SHOWER HEATER TEMPERATURE CONTROL
   
   GAS HOT WATER TEMPERATURE CONTROL
   
   INDIRECT WATER HEATER TEMPERATURE CONTROLS
   
   OIL HOT WATER HEATER TEMPERATURE CONTROL
   
   SCALDING TEMPERATURES & TIMES
   
   TANKLESS HOT WATER HEATER TEMPERATURE CONTROL
   


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 VALVE, WATER HEATER where we also discuss procedures for testing water heater pressure/temperature relief vales.
   
   
   Proper relief valve location: In Carson Dunlop Associates' sketch at left the pressure relief valve is improperly installed on the far side of the pressure reducing valve at the water heater.
   
   Watch out: This is an example of a very dangerous installation. Thanks to Carson Dunlop Associates, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.
   
   In some locations where hard water is found or where water supply piping materials cannot withstand higher pressures, a thermal expansion control valve is also used to drain excess hot water tank pressure. These separate water system expansion control valves, discussed below.
   
   Proper TPR discharge or drain piping: improperly installed, routed, sized, connected drain piping at a water heater risks scalding a bystander or a catastrophic BLEVE explosion.
   
   See RELIEF VALVE DISCHARGE TUBE
   
   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).
   
   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.
   
   More about temperature/pressure relief valves or TPRs is
   
   at RELIEF VALVES - TP VALVES
3. Automatic gas shutoff valves for gas fired water heaters,
   
   temperature-controlled, will turn off the fuel supply to the heater if its temperture becomes unsafe.
   
   Details are at GAS WATER HEATER AUTOMATIC SHUTOFF
4. Gas line fire safety valves will shut off the fuel supply to a gas-fired water heater in the event of a nearby fire.
   
   Details are at GAS LINE FIRE SAFETY VALVES
5. Water heater or cylinder 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
   
   FLUE GAS SPILL SWITCH TRIPPING & RESET
   
   PLASTIC PLEXVENT ULTRAVENT RECALL.
6. Water heater or cylinder 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.
7. Water heater or cylinder clearance distance & 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, METAL CHIMNEYS
   • FIRE CLEARANCES, SINGLE-WALL METAL FLUES
     
     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]. - Information from Village of Mt. Prospect
     
     Gas Water Heater Clearance Distances & Working Space - Calorifier or geyser clearances
     
   • Water heaters require clearance space at least at the heater front for service.
   • At back or sides clearance specifications vary by manufacturer and can be quite small. Here is an example of water heater clearance distances from an A.O. Smith water heater installation manual:
   • Minimum clearances between the water heater and combustible and noncombustible construction are:
   • 0 in. (0mm) from sides of the gas fired water heater
   • 0 in. (0mm) from back of the gas fired water heater
   • 4 in. (102mm) from front of jacket to closet door of the gas fired water heater
   • 20 in. (508mm) from top of jacket of the gas fired water heater to combustible and noncombustible material.
   • Minimum vent clearance:
   • 1 in. (25mm)* for the gas fired water heater
   • Provide 3 ft. (915mm) front of the gas fired water heater - clearance for servicing and adequate clearance between the jacket top & ceiling for servicing the flue area

   Source: A.O. Smith, INSTRUCTION MANUAL, GAS WATER HEATERS MODEL GDV GDVT [PDF] A.O. Smith Water Heaters, 500 Tennessee Waltz Parkway, Ashland City, TN 37015 USA, Tel: 1-800-433-2545 Website: www.aosmithwaterheaters.com Email: parts@hotwater.comretrieved 2018/05/04, original source: www.hotwater.com/lit/im/res_gas/186589-000.pdf

   Watch Out: The safe clearance distances for water heaters will vary by all of those features. So you'll want to find the brand and model of your water heater, and then find its service manual and check the specific distances given for your particular heater.
   
   
   Oil Fired Water Heater Clearance Distances & Working Space
   

   • Provide ample clearance for the oil fired water heater on all sides for installation, adjustment, and replacement of burner, control components and other serviceable parts, such as the relief valve, power burner, thermostat, and/or drain valve.
   • Minimum clearance from oil fired water heater to combustible construction is: Sides, 6”, Back, 6”, Front, 24”.
   • If a chimney connector is used, the minimum clearance from the top of the oil fired water heater to the connector is 18”.
     
     Source: HTP OIL FIRED WATER HEATER INSTALLATION MANUAL [PDF] retrieved 2018/05/04, HTP Products, 120 Braley Rd. P.O. Box 429 East Freetown, MA 02717-0429 USA, Website: www.htproducts.com, original source: http://www.htproducts.com/literature/lp-340.pdf

   See WATER HEATER AGE & MANUALS
   
   Tankless Water Heater Clearance Distances & Working Space
   
   Using a Reliance Tankless Water Heater manual as an example, you need to maintain working space distances and fire clearances around the heater including at least:

• 12 - 36" from the tankless water heater top, depending on model
• 12" from the tankless water heater bottom
• 4"to 24" from the tankless water heater front, depending on model
• 1" from the tankless water heater back
• 3" from the tankless water heater sides
  
  Source: RELIANCE TANKLESS WATER HEATER MANUAL INDOOR Model TS-110-GI [PDF] Indoor Tankless watre heater, non-condensing 140K BTU Natural Gas
8. Water heater or cylinder 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.
9. 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
   
   See details
   
   at PROTECTION BOLLARDS for MECHANICAL EQUIPMENT
10. Earthquake Strapping for water heaters: 
    
    is required in earthquake zones.
    
    Water heaters must be secured against independent movement to reduce the chance of fire in the event of an earthquake
11. 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.

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12. 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"

    Appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in garages.

    For the purpose of this section, rooms or spaces that are not part of the living space of a dwelling unit and that communicate with a private garage through openings shall be considered to be part of the garage.
    
    See details at ELEVATE OIL or GAS BURNER 18" ABOVE GARAGE FLOOR - IRC Requirement
    
    Also,

    Appliances shall not be installed in a location subject to vehicle damage except where protected by approved barriers.
    
    See details at PROTECTION BOLLARDS for MECHANICAL EQUIPMENT

    Original source of the text and illustration above:

    • Stevens WA, COMMONLY USED RESIDENTIAL BUILDING CODES, IRC 2009, [PDF] retrieved 2019/05/08 original source: co.stevens.wa.us/landservices/documents/MECHANICALSECTION.pdf
    • Other sections of this mechnaical code are given
      
13. 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).
14. 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.

15. Thermal Expansion Tanks & Thermal Expansion Control Valves 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.
    
    Amtrol Inc. provides the THERM-X-TROL® line of thermal expansion shock absorbers - expansion tanks for domestic hot water systems. Quoting from the company's product literature:
    
    Thermal expansion occurs as domestic water is heated. Left unchecked, the resulting pressure increase can cause relief valve discharge and other potentially unsafe conditions. Therm-X-Trol® expansion tanks absorb this expanded water, keeping water pressure at a safe level.
    
    Water heater manufacturers and plumbing codes require the installation of an expansion control device if a backflow preventor, pressure reducing valve or check valve is installed in the domestic supply line. Therm-X-Trol satisfies all manufacturers' requirements. - Amtrol (2014)
    
    An expansion tank or additional pressure/temperature relief valves can prevent these problems and may also extend the life of the water heater. Details are
    
    at HOT WATER EXPANSION TANKS
    
    and
    at HOT WATER EXPANSION VALVES
16. Flame shield on gas or oil fired water heaters or cylinders:
    
    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.
17. Gas shutoff valves for water heaters:
    
    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, LP or NATURAL.
18. Gas piping and gas piping drip leg on gas fired water cylinders / heaters:
    
    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 CLEARANCES, CODES & DEFECTS.
    
    Also see GAS LEAK DETECTION, LP / NG.
    
    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.
19. Home heating using a water heater:
    
    may be taxing the equipment beyond its intended use. See
    
    WATER HEATERS for HOME HEATING USE?
20. 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
21. Insulation on water cylinders / water heaters:
    
    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?.
22. Leak pan and drain beneath water heaters:
    
    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.
23. 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.
    
    
24. Location of gas fueled water heaters, LPG:
    
    prohibited or restricted locations for LPG appliances: storage closets, bedrooms, bathrooms
    
    

    
    IRC Mechanical Code 70. LPG APPLIANCES. Section M2005 IRC 2009
    
    M2005.2 Prohibited locations.
    
    Fuel-fired water heaters shall not be installed in a room used as a storage closet.
    
    Water heaters located in a bedroom or bathroom shall be installed in a sealed enclosure so that combustion air will not be taken from the living space.
    
    Direct-vent water heaters are not required to be installed within an enclosure.
    
    M2005.2.1 Water heater access.
    
    Access to water heaters that are located in an attic or under floor crawl space is permitted to be through a closet located in a sleeping room or bathroom where ventilation of those spaces is in accordance with this code.

    Original source:

    • Stevens WA, COMMONLY USED RESIDENTIAL BUILDING CODES, IRC 2009, [PDF] retrieved 2019/05/08 original source: http://www.co.stevens.wa.us/landservices/documents/MECHANICALSECTION.pdf
    • Other sections of this mechnaical code are given at CHIMNEY HEIGHT & CLEARANCE CODE
25. Mobile home water heater safety:
    
    see MOBILE HOME WATER HEATER DEFECTS
26. Noises at the water heater:
    
    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.
27. Odors at the water heater::
    
    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
    
    See 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
28. 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.
29. 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 SUPPLY LINE SAFETY VALVES, OSVs.
30. PEX plumbing errors at water heaters:
    
    PEX should not be connected directly to a water heater but should first be separated by at least 18" of copper to reduce the risk of temperature damage to the PEX piping and subsequent leaks.
    
    Where PEX is used for a water heater TPRV or "relief valve" discharge tube, check the relief valve and water heater manufacturer's instructions to be sure that the relief valve discharge tube diameter reduction and thus flow construction caused by noraml PEX connectors is acceptable.
    
    See details at PEX CONNECTIONS to WATER HEATERS
    
    
31. Spill switch on gas flues for water heating appliances:
    
    Gas fired water heaters should have a flue gas spillage switch that shuts off the gas valve if needed. See details
    
    at FLUE GAS SPILL SWITCH TRIPPING & RESET.
32. Tankless coils used for producing domestic hot water can present a special scalding risk.
    
    See ANTI SCALD VALVES
    and
    
    see TANKLESS COILS.
33. A Water Heater 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.
34. Water pressure reducing valves / water pressure regulators for water heaters:
    
    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.
    
    WATER PRESSURE REGULATOR ADJUSTMENT discusses how to adjust a water pressure regulator to the proper setting.  
35. Working space around the water heater:
    
    Water heaters require safe working space around the device regardless of the heater type.
    
    Examples of water heater working space are found at
    
    WATER HEATER or HOT WATER CYLINDER CLEARANCE DISTANCES & cleareance to combustibles
    
    Specific clearances for working space at the water heater are given in the individual heater's installation manual.

Building Codes & 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 INSPECDTION, 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
• WATER HEATER INSTALLATION INFORMATION, Bulletin 293 [PDF] (2020) City of San Jose, Planning, Building & Code Enforcement, Development Services Permit Center San José City Hall 200 E. Santa Clara St. San José, CA 95113 408-535-3555 www.sanjoseca.gov/permitcenter

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

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 RELIEF VALVE, WATER HEATER
2. Hot water expansion tanks: handle the pressure increase from normal water heating and prevent dangerous dripping at the TPR valve on the heater
   
   See HOT WATER EXPANSION TANKS
3. Spill switch on gas flues: Gas fired water heaters should have a flue gas spillage switch that shuts off the gas valve if needed
4. Gas shutoff valves: Gas fired water heaters in some jurisdictions require an automatic gas shutoff valve that responds to high water heater temperature.
   
   See GAS WATER HEATER AUTOMATIC SHUTOFF
   
   and
   GAS LINE FIRE SAFETY VALVES
5. 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 OIL LINE SAFETY VALVES, OSV
6. 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.
7. 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.
8. 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.
9. 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:
   
   see  MIXING / ANTI-SCALD VALVES 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.
10. Working space:
    
    Water heaters require safe working space around the device regardless of the heater type
11. Damage protection:
    
    Water heaters in garages should be protected from mechanical damage such as being struck by an auto
12. 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.
13. 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.

We list and compare different types of water heating systems

at WATER HEATER COMPARISONS, PROPERTIES

...

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: should this water heater be "red-tagged"

I am a tenant who found this the other day on a 35 year old water heater: (see pics) Then this and another pressure relief valve on a furnace boiler were overlooked for code violations in an official inspection--which I arranged-- which took all of five minutes...there are other things I might mention.

I wish the water heater were red-tagged, but you know I'm only a tenant.

Who, besides a willing contractor/plumber (which tenants aren't supposed to hire in this state) can (red tag)? From what I understand, if it's still functioning, an ordinary inspector will give an appliance a passing grade and therefore the official "okay" (happened already).

They don't seem to care to look as closely at things like temperature and pressure relief valves as your inspection website does--but I wish... Where could I have found such care and expertise in an inspector the first time? - Anonymous by private email 2021/05/05

Moderator reply: who does equipment red-tagging on an unsafe Rheem electric water heater like this one?

A water heater with a pressure relief valve discharge tube that is down-sized from the manufacturer's original outlet or the relief valve outlet is unsafe, risking a BLEVE explosion.

See details at

RELIEF VALVE DISCHARGE TUBE

Any home inspector or building code compliance inspector would be expected to cite this as an unsafe condition.

Watch out: even an incomplete inspection of your water heater from just your photos one can see multiple water heater safety questions at this installations.

"Red tagging" is typically done by a service technician.

Other inspectors (building code inspector or home inspector) are expected to identify visually-detectable unsafe conditions and to write up the issue, and because it's a life-safety concern, for conditions that in the inspector's opinion are urgent, the inspectorought to notify all parties concerned, including owners and occupants of the building - in writing and orally.

The cost to cure for an improper TPR dischagre tube is trivial: a few dollars in plumbing parts and, of course, the plumbers labor charge. Your landlord might want to compare that cost to the potentially enormous cost should the water heater suffer a BLEVE explosion.

Details on relief valves are

at RELIEF VALVE, WATER HEATER

You are very welcome to post additional photos and comments (one photo per comment, as many comments as you need) - on any of these pages: sometimes by exposing an unsafe condition to the sunshine of public view a building manager or owner will be prompted to act.

Obvious safety concerns at this water heater include the following:

1. Temperature-pressure relief valve (TPRV) discharge tube down-sized from 3/4" to 1/2" risking a BLEVE explosion
   
   See BLEVE EXPLOSIONS
2. TPRV discharge tube too short: if the valve opens someone nearby could be scalded
3. TPRV discharge tube partly covered - its condition cannot be visually determined
4. TPRV leaks: there appears to be a water droplet at the outlet of the discharge tube, possibly indicating a TPR valve leak and risking an ultimate TPRV blockage and BLEVE explosion
5. PEX water piping is connected directly to the water heater top, omtting the required 18" copper stub between heater top and first PEX piping connection - risking a plumbing leak or burst hot water pipe
6. Questionable duct-taped access cover to 240VAC electrical connections and heater controls - possible shock hazard to occupants if the cover is not secure
7. Questionable use of an insulating blanket (generally unnecessary) on the heater - could cover other defects, leaks, hazards

Details about PEX connections to water heaters are discussed below.

Reader follow-up:

Something I didn't mention, but which shows on the picture of the water heater which I sent earlier, are the two hot and cold PEX lines leading directly to the top of the tank.

If the T&P valve is still functional, I understand it won't open before it gets hotter or up to a higher pressure than is good for PEX ...so with this configuration is a failure at the top of the tank before the water can vent through its proper channel (the T&P valve) unheard of? - Anonymous by private email 2021/07/01

Moderator reply:

Please see your question and our reply now

at PEX CONNECTIONS to WATER HEATERS

On 2019-12-13 - by (mod) - do water heater inspections provide a report of findings?

I'm not sure, Gloria.

When a water heater is leaking and is replaced, depending on the country and city where you live, a code-compliance inspection is often required after the new heater is installed.

The code inspector will "pass" or "fail" the installation.

If she finds reason to "fail" the installation then the reason or the corrective measures the inspector requires will of course have to be provided to you or to the installer directly.

If you're hoping to have future recourse should something go wrong later-on, in my OPINION that's not likely to be successful.

If you already see something that makes you worry, tell me what that is, and give your installer or your building inspector a call and ask them about it; let me know what you're told.

On 2019-12-13 by Gloria

I actually just asked a question about inspections and permits. Could I get a response about whether or not I should get a report from the inspector. I never saw the inspector and I need to be assured that the new water heater is up to code and will not cause a hazard in my home.

I had a company come to my home to replace my leaking gas water heater. Should I have seen the permit and an inspector report?

The installer claims the inspector came by and inspected the heater. However, I was at home during the installation and never saw anyone come to inspect. I called and asked the company about an inspection report and they said they would get back with me tomorrow (12-13-2019.

On 2017-03-27 - by (mod) -

Re-posting without link

Ken said:
Thanks for the great info. Really in depth. Great stuff. Thank you for sharing. Plumber Columbia SC

Thanks Ken.
While our security doesn't permit comments to include posted links nor ads, you can certainly be linked-to from InspectApedia pages by using our page top or bottom CONTACT link to suggest any technical content additions or corrections. We welcome input and help from professionals and experts and are glad to cite and refer our readers to them.

Daniel

On 2017-03-22 1 - by (mod) -

Teresa:

If the heater is an ELECTRIC unit I think that's ok. Naturally you wouldn't do that on a gas or oil fired hot water cylinder as that'd be a fire risk.

Also I'd like to know more about your cylinder: modern water heaters are already insulated and don't need an extra external insulating jacket, and if the jacket covers the temperature/pressure relief valve, the system is unsafe.

You can use the page top or bottom CONTACT link to send me some photos of the heater and any data tags that identify it and give model number and I can research further.

Daniel

On 2017-03-22 by Teresa Lander

We have a hot water cylinder with a padded insulating jacket. The cat is tearing at the jacket, either for fun or to get to sleep on top of the warm cylinder. Would it be a fire hazard to keep her out by packing the space on top of the cylinder with cardboard boxes as a temporary measure? And any suggestions for a more permanent solution? Thank you!

On 2015-07-09 - by (mod) -

Abbas

You don't give the country and location; in general as long as the electric geyser installation meets your local codes you should be fine. Be sure to pay attention to electrical wiring codes as well as temperature and pressure relief valve and discharge tube codes.

On 2015-07-09 by Abbas

Please advise if it is safe to install an automatic electric geyser inside a washroom?

...

Continue reading  at WATER HEATER TEMPERATURE TOO COLD or TOO HOT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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Suggested citation for this web page

WATER HEATER SAFETY at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER HEATERS

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