Water Heater Installation, Seismic Bracing, Thermal Expansion and Defects

Installing a water heater in a garage

Ignition source elevation

The ignition source of a water heater or other appliance in a garage should be 18 inches or more above the floor. Furnaces, heat pumps, and similar appliances are covered too, whether they use gas, oil, or electricity. The 18 inches is measured to the ignition source, so the bottom of the appliance counts only if the ignition source is located there.

An FVIR listed water heater is not required to be elevated. Depending on the jurisdiction, elevation may be required for a clothes dryer.

Impact protection

In a garage, a water heater or other appliance should have protection from vehicle impact damage. It is usually provided by a tire stop, by a bollard, which is a steel post, or by framing that encloses the appliance, such as an alcove. Framing that protects the appliance can still block access, as shelves built across the front of a water heater do.

Seismic bracing

In seismic risk areas, a water heater should be anchored or strapped so that it resists movement during an earthquake, and the common guidelines for this vary by jurisdiction.

Anchors or straps should be in the upper third and the lower third of the water heater, and they should not interfere with service access openings. The anchoring of each strap to framing should be adequate. A strap should be at least 4 inches from the controls, measured from each strap down to the control below it. In these areas, a gas water heater is often required to connect to the gas supply with a flexible gas connector.

Thermal expansion

Closed systems

Thermal expansion is the increase in the volume of water as it is heated. When water is heated in a typical 50 gallon tank, it can expand by 1/2 gallon or more. In most cases, it flows back into the cold water supply.

Devices such as a pressure reducing valve, a check valve, or a water meter check valve sometimes block that return. A cold water supply system blocked by one of them is a closed system, and newer houses more commonly have closed systems.

In a closed system, the hot water may expand into the house water distribution system. The increased pressure can break hoses and tubes, such as ice maker tubes and the hoses on clothes washing machines and dishwashers. It can also make fixtures and toilet fill valves leak. The hot water may instead remain in the water heater, where it can make the TPR valve leak. In extreme cases, it may even damage the water heater itself.

Thermal expansion devices

Where the cold water supply is closed, the recommendation is a thermal expansion device. Three available devices let the water expand without damage to the water distribution system:

1. a thermal expansion tank
2. a thermal expansion valve that drains outdoors or to an internal receptor
3. a toilet fill valve with an integrated thermal expansion valve

Each device should be installed according to the manufacturer's instructions. The tank and the drained valve should be on the cold water supply pipe, close to the water heater, with the other valves and devices upstream. The toilet fill valve device is the exception to this location.

Thermal expansion tank

In a house, a thermal expansion tank is usually about 2 gallons. A bladder inside it keeps the water apart from pressurized air. Water enters the tank as needed, and the air pushes it back out when the expansion pressure subsides.

The tank may go in any orientation, and support may be appropriate where it connects to a vertical pipe. Testing the tank is outside the scope of a home inspection. A home inspector who chooses to test one may use a tire pressure gauge to check the tank's air pressure at its air valve.

The reading usually falls between 20 and 40 psi, depending on the tank and the incoming water pressure. A reading under 20 psi usually means the tank needs air added. If water flows from the air valve, the tank should be replaced because it has failed.

Thermal expansion valve at the cold water shutoff

A thermal expansion valve may be combined with the cold water shutoff of a water heater. A drain tube running from the device outdoors, or to a receptor, for example a floor drain, may identify this combination. The valve opens at a set pressure and lets the water drain. There is no test method a home inspector may use for this valve.

Thermal expansion valve in a toilet fill valve

A thermal expansion valve may also be built into a toilet fill valve. If the label on the vertical tube of the fill valve is intact, it may identify this combination. At a set pressure, the valve opens and drains into the toilet tank and the overflow tube. The device should go in the toilet nearest to the water heater. Manufacturers recommend annual testing, but there is no test method a home inspector may use for this valve. The Watts Governor 80 is a common version.

Mixing valves

A mixing valve, also called a tempering valve, limits the water flowing through it to a temperature of not more than 120 degrees F to prevent scalding injuries. Bathtubs and showers require a mixing valve, and newer single handle faucets usually have one built in. Occasionally a mixing valve is installed as a separate device near a water faucet, or near the water heater.

A mixing valve is adjustable, and it may be identified by its hot water outlet and its hot and cold water inlets. Testing a mixing valve is outside the scope of a home inspection. A home inspector may attempt an inspection by measuring the water temperature at the fixture.

Typical defects, all water heaters

Home inspectors should report these typical defects in all water heaters:

1. Cold water shutoff valve absent, leaking, or significantly corroded
2. Flexible water connectors crimped or damaged
3. Dielectric fitting absent between dissimilar metals
4. Appliance in a garage without vehicle impact protection
5. Cabinet physically damaged
6. Water temperature too high
7. Foul odor in the hot water

Typical defects, storage tank water heaters, all types

Home inspectors should report these typical defects in storage tank water heaters of all types:

1. Visible leaks or leak evidence on or around the cabinet
2. Visible leaks or leak evidence behind access openings
3. Visible leaks or leak evidence at the drain valve
4. Drain valve capped, often because it is leaking
5. Drain valve absent
6. Access or clearance inadequate for operating, service, or replacement
7. Clearance to combustibles inadequate
8. Tank or tank support unstable
9. Ignition source not raised in a garage
10. Tank not strapped where strapping is required
11. Drain pan and pipe absent or incorrectly installed
12. Access covers absent
13. Thermal expansion device not installed where recommended

Typical defects, gas and oil storage tank water heaters

Home inspectors should report these typical defects in gas or oil storage tank water heaters:

1. Significant rust or debris in the combustion chamber
2. Visible leaks or leak evidence inside or around the combustion chamber
3. Visible scorching or soot around the combustion chamber opening
4. Draft hood or vent system loose, disconnected, or improperly installed
5. Flue baffle collapsed into the combustion chamber
6. Water heater noisy while operating
7. Combustion air inadequate
8. Plastic pipe connected directly to the water heater (check the pipe manufacturer's instructions)
9. Damaged gas control valve, or temperature control not working properly

Typical defects, electric storage tank water heaters

Home inspectors should report these typical defects in electric storage tank water heaters:

1. Visible leaks or leak evidence around heating elements and behind access covers
2. Heating elements not operating; the lower element is usually the one
3. Thermostats not operating properly
4. Element wattage not as specified on the water heater label
5. Visible scorching at the access covers or the power supply connections
6. Grounding wire not connected to the cabinet
7. Electricity supply wiring method improperly installed

Typical defects, relief valves and discharge pipes

Home inspectors should report these typical defects in relief valves and discharge pipes:

1. Relief valve absent
2. Relief valve more than 6 inches below the tank top
3. Relief valve leaking
4. Discharge pipe absent or improperly installed

Standards: (1) IRC 2018: P2903.4 (thermal expansion), M2005 (water heaters), Table E4101.5 (electrical disconnecting devices), and Chapter 28 (water heaters); (2) manufacturer's instructions.

Numbers and Rules to Memorize