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.
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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.
How to Inspect the Safety of Domestic Hot Water Heaters - 31 inspection points
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. Our photo (left) 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.
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.
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. 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 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. 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.
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.
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.
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
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
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.
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
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
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.
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"
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).
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.
Expansion Tanks & Thermal Expanson 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. 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.
Question: should I replace the water heater thermal expansion valve on the cold water inlet side of my water heater with a water heater thermal expansion tank?
I have a thermal expansion valve that is installed on my inlet line (cold water line going into my hot water tank) that is leaking, now the question that I have is, is it required to be on the inlet line . Talking to a few friends that do plumbing and they are saying that it is not required, but they recommend that I install a expansion tank. So, another question is if the system was installed without a expansion tank is it a good idea to install one are just replace the thermal expansion valve that was installed when the hot water tank was installed, are just remove the old system and install a new hot water tank system per new system directions ? So many questions, but can't find all the answers! - C.D. 12/23/12
Reply: what's the difference between an expansion control valve and a water heater thermal expansion tank & how are they installed & used?
A thermal expansion control valve is essentially a pressure relief valve installed at a water heater to prevent forming excessive pressures in the closed loop of water supply piping and water pressure tank when water is heated at the water heater. A thermal expansion valve is then in essence a safety device that will open and spill water and pressure to prevent plumbing equipment or piping damage or worse, unsafe conditions.
(See BLEVE EXPLOSIONS) . Expansion control valves are produced by a variety of companies including Watts & Wilkins-Zurn who produce a variety of thermal expansion control products including valves and pressure tanks.
We see thermal expansion control valves installed as an "extra" pressure relief valve in buildings installed on the water piping itself where the water suppy piping is not rated as capable of withstanding the normal pressures that may otherwise develop in a hot water system.
The thermal expansion control valve installed on water piping at the water heater is typically rated to open at 100 psi.
Watch out: As Carson Dunlop Associates point out in our text earlier in this article, a thermal expansion control valve can be located on building water supply piping apart from mounting on the water heater itself. However, the thermal expansion control valve cannot be located where it is separated from the water heater by a stop valve nor by a pressure reducing valve, as doing so can prevent the thermal expansion control valve from safely sensing increased water pressure created by the water heater.
Watch out: where you see an "extra" 100-psi-rated thermal expansion control valve at a water heater, you should understand its presence to also mean that the water supply piping in the building might be a plastic product that is less strong (and potentially less reliable against leaks and breakages) than copper water supply piping. An example of piping where a thermal expansion control valve is often found is Flow-Guard Gold® CPVC water supply piping produced by Charlette pipe, rated for 100 psi at 180 degF. Note that the rated working pressure and temperature ratings of different pipe products from different manufacturers varies. For example, quoting from Georg Fischer GF Harvel CPVC pipe
CPVC pressure pipe has an upper working temperature limit of 200°F (93°C), or approximately 60°F (15°C) above that of Type I Grade I PVC. As with all thermoplastic piping systems, CPVC’s ability to withstand pressure varies with pipe diameter, wall thickness, and temperature. For pressure piping applications it is recommended for temperatures as high as 200°F (93°C) when appropriate temperature de-rating factors are applied. As the pipe diameter and temperature increases, the pressure rating of the product decreases. For example, 1/2" Schedule 80 CPVC pipe is engineered for continuous service of 850 psi @ 73°F (23°C). The same pipe in service @ 180°F (82°C) carries a maximum working pressure rating of 210 psi at this temperature. 6" Schedule 80 CPVC pipe is designed for 270 psi @ 73°F, and 54 psi @ 200°F. [1]
Normal pressures in a hot water heater and piping can reach levels a bit below 150 psi. Above that 150 psi level, water will spill from the standard pressure & temperature relief valve (RELIEF VALVES - Water Heaters) installed on the water heater itself.
You should not normally see water spilling from the thermal expansion control valve - if you do, the system is not operating properly and inspection/adjustments/corrections are needed.
We are researching water expansion control valves further, as we noted in 2011 that Zurn had discontinued production of the type of thermal expansion control valve found installed directly on water supply piping at the water heater.[3]
Water heater expansion tanks, in contrast, are intended to absorb water piping system and water tank pressure increases without causing inappropriate spillage from pressure/temperature relief valves attached to the system, so long as water pressure and temperature at the water heater remain in the safe range specified by the manufacturer.
We recommend water heater expansion tanks in many installations, as you can read above. But these are not an "either-or" solution. If your water piping is plastic CPVC it may require the added protection of a secondary lower-pressure pressure relief valve.
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.
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.
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, 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.
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
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?.
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.
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.
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.
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
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.
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.
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.
Tankless coils used for producing domestic hot water can present a special scalding risk. See ANTI SCALD VALVES and see TANKLESS COILS.
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.
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. WATER PRESSURE REGULATOR ADJUSTMENTdiscusses how to adjust a water pressure regulator to the proper setting.
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.
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
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
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.
Spill switch on gas flues: Gas fired water heaters should have a flue gas spillage switch that shuts off the gas valve if needed
Gas shutoff valves: Gas fired water heaters in some jurisdictions require an automatic gas shutoff valve that responds to high water heater temperature.
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.
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.
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.
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.
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.
Working space: Water heaters require safe working space around the device regardless of the heater type
Damage protection: Water heaters in garages should be protected from mechanical damage such as being struck by an auto
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.
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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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
[1] Georg Fischer Piping Systems, "CPVC Pipe", retrieved 12/23/12, GF Piping, Pennsylvania
300 Kuebler Road
Easton, PA 18040
phone (610) 252-7355, original source http://www.harvel.com/piping-systems/gf-harvel-cpvc-industrial-pipe, copy on file as GF_CPVC Industrial Pipe _ CPVC Pipe.pdf.
[2] Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
home inspection educator.
[3] Zurn Engineered Water Solutions, retrieved 12/23/12, original source: http://www.zurn.com/Pages/ProductsList.aspx?NodeKey=398872
(Model BR4EC - Water Pressure Reducing Valve With Thermal Expansion Relief Valve … Discontinued Products,Pressure Reducing Valves,Wilkins Water Control,,R4EC,4EC)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program. Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Home Reference Book, a reference & inspection report product for building owners & inspectors. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
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.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
Carson, Dunlop & Associates Ltd.,
The Home Reference Book - the Encyclopedia of Homes