At IM Home Inspections, we find a large number of water heaters we come across have one or more problems due to poor installation. And we often find people believing myths about how a water heater should be installed.
Let’s look at the Top 10 Myths of Water Heater Installations.
Note: this article only applies to California.
Myth 1: An expansion tank is just to hold extra water in case I run out.
Truth: An expansion tank is partially filled with air and is designed to absorb excess water pressure caused by thermal expansion. Remember, when water is heated, it expands. That expanding water needs to go somewhere. In an open plumbing system, the expanding water can push back down the pipe to the city water supply. However, in most Los Angeles area homes, we have a pressure-reducing valve to regulate the water pressure inside a home. Once a pressure valve is installed, the expanding hot water can not simply travel backward into the city line. The valve creates what is known as a closed system.
California plumbing code says
608.3 Expansion Tanks, and Combination Temperature and Pressure-Relief Valves
“A water system provided with a check valve, backflow preventer, or other normally closed device that prevents dissipation of building pressure back into the water main, independent of the type of water heater used, shall be provided with an approved, listed, and adequately sized expansion tank or other approved device having a similar function to control thermal expansion. Such expansion tank or other approved device shall be installed on the building side of the check valve, backflow preventer, or other device and shall be sized and installed in accordance with the manufacturer’s installation instructions.”
Myth 2: A tankless water heater does NOT need an expansion tank
Truth: California plumbing code says 608.3
“A water system provided with a check valve, backflow preventer, or other normally closed device that prevents dissipation of building pressure back into the water main, independent of the type of water heater used, shall be provided with an approved, listed, and adequately sized expansion tank “
The code specifically does not exempt tankless water heaters.
In addition, every tankless water heater installation manual I have read so far has said an expansion tank is required on closed plumbing systems.
Further, many manufacturers make expansion tanks specifically for tankless water heaters, such as the ZEP-1 Stainless Steel Thermal Expansion Tank, among others.
Myth 3: A bonding wire has nothing to do with my water heater
Truth: A bonding wire, connecting the hot water, cold water, and gas pipes serves two purposes. One, in a water heater, you have the copper that meets the steel fittings on the water heater which are subject to a slight electrical potential, called electrolysis, that can lead to corrosion. A bonding wire allows this faint current between the water pipes to bypass the copper-to-steel fittings and reduce corrosion.
Secondly, the home’s electric grounding system is usually connected to the cold water inlet pipe to the home. Both gas and water metal pipes should be grounded. A water heater creates a break between the cold water pipes and the hot water pipes in the home. By bonding the cold water pipe to the hot water pipe and to the gas pipe at the water heater to the gas pipe, helps to ensure that the entire water and gas plumbing system will be electrically grounded.
This is covered in the California electrical code 250.104
Myth 4: A TPR Valve can discharge to the floor
A temperature relief valve, commonly called a TPR or TPRV, is a device that prevents water heaters from exploding. If a water heater overheats, it can become damaged or explode and cause significant damage to both property and people. A TPR valve is a special valve that opens and releases hot water from the water heater should the water heater overheat. They are required by California Plumbing Code 505.2.
TPR valves must be connected to a discharge pipe. The old code simply said the pipe must terminate not less than 6 inches from the floor. The problem is all that hot water would ruin the areas around the water heater. So in 2010, the code was modified, and now says
608.5(3) Discharge Piping
“Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or outside of the building with the end of the pipe not exceeding 2 feet (610 mm) and not less than 6 inches (152 mm) above the ground and pointing downwards.”
By running the discharge pipe outside the home, the chances of property damage are reduced.
Myth 5: A TPR Valve can discharge into the drip pan
Truth: If a TPR valve were to open and shoot out hot water, a drip pan would not be able to catch and drain the water quickly. Rather, the hot water would just splash out and damage the area around the water heater, making the entire point of a discharge pipe null.
Code puts is plainly
608.5(7) “Discharge from a relief valve into a water heater pan shall be prohibited.”
Myth 6: Small Water heaters do not need to be strapped
507.2 Seismic Provisions
“Water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion. Strapping shall be at points within the upper one third (1/3) and lower one-third (1/3) of its vertical dimensions. At the lower point, a minimum distance of four (4) inches (102 mm) shall be maintained above the controls with the strapping.”
No provision or exception is made for smaller water heaters.
Myth 7: Large Water Heaters need 3 or 4 straps
Truth, California Plumbing Code 507.2 Seismic Provisions makes no reference to size. It’s common to hear people say that 75-gallon water heaters need 3 straps or 100-gallon water heaters need 4 straps, but there is no provision in California Plumbing Code that backs up these claims.
Myth 8: A water heater drip pan is only a suggestion, but not required
Truth: Drip plans are required in the California Plumbing Code
507.5 Drainage Pan
“Where a water heater is located in an attic. in or on an attic-ceiling assembly, floor-ceiling assembly, or floor-subfloor assembly where damage results from a leaking water heater, a watertight pan of corrosion-resistant materials shall be installed beneath the water heater with not less than 3/4 of an inch (20 mm) diameter drain to an approved location.”
This means unless the water heater is located outside, or somehow installed in a manner that a drip won’t cause water damage to the surrounding area, a drip pan is required. And the drainpipe should go somewhere that also will not cause damage to the surrounding area.
Myth 9: A water heater must be 18″ above the garage floor
Truth: At one point in time, this was indeed true. The reason was water heaters used to have an open flame, and fumes from gasoline, paint thinner and other flammables found in a garage could potentially come in contact with the open flame. 18 inches was thought to be enough to prevent such fumes that linger near the ground from coming in contact with the open flame. But starting in mid-2003, 50 gallon and smaller water heaters started being made with flammable vapor ignition resistant (FVIR) construction, which eliminated this problem. Water heaters larger than 50 gallons followed soon after. Now it is impossible to buy a water heater that is not FVIR.
Code now says,
507.13 Installation in Garages:
“In garages and in adjacent spaces that open to the garage and are not part of the living space of a dwelling unit shall be installed so that burners and burner-ignition devices are located not less than 18 inches (457 mm) above the floor unless listed as flammable vapor ignition resistant.”
So unless a home had a very old water heater, the 18-inch rule no longer applies. And if you have a pre-FVIR water heater, chances are it is due to be replaced.
Myth 10: My water heater will last for years to come
Truth: The average water heater will last 6 to 12 years. Most water heaters require regular maintenance, even tankless, and the truth is few people ever maintain a water heater, and there is no visible way to tell if a water heater has had regular maintenance. As such, a perfectly good working water heater today may not work tomorrow. At IM Home Inspections, we visually check the water heater, and then we check for hot water at every faucet. But even that can not guarantee a water heater will remain functional.
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