Water heaters in mobile or manufactured homes are very similar to conventional water heaters used in site-built homes, but there are some critical differences between the two types. Most importantly, water heaters for mobile homes must be rated for mobile home use. All heater installations must include sufficient space and ventilation for the equipment, and the heater tanks must be secured to prevent movement.
The following how-to steps outline the basic procedure for replacing a standard (not sealed-combustion) water heater in an exterior compartment of a mobile home. Specific installation steps and requirements may vary by area and your particular water heater.
HUD and Code Approval
Mobile home water heaters must meet specific standards established by the U.S. Department of Housing and Urban Development (HUD). All heaters approved for use in manufactured homes carry a label indicating HUD compliance. Using a standard, non-compliant unit in a mobile home will likely run afoul of the local building code and can lead to other problems. Home insurers may not honor claims related to non-compliant water heaters, and non-compliant heaters can create roadblocks when selling a home.
Water heaters designed for manufactured homes typically have a few specific features:
- Side-mounted cold water inlet (sometimes the hot water outlet is also at the side of the tank)
- Meets HUD standards for insulation and energy efficiency
- Non-adjustable temperature-and-pressure relief (TPR) valve
- Smaller overall size than comparable standard units (in some cases)
- Gas heaters are sealed-combustion if installed indoors
Water Heater Fuel Types
In most cases, water heaters are replaced with new units that use the same fuel source as the original. The most common fuel types are electric and gas, but there are also some fuel-oil units. Gas heaters may use propane or natural gas, depending on the home's supply. It can be costly to convert to a different fuel type as part of a replacement project, but it is possible.
Electric units must have sufficient capacity in the home's electrical panel and typically require a dedicated 240-volt circuit, while gas heaters need a gas supply and special accommodations for combustion air and exhaust.
Installing new circuits or plumbing connections for a different fuel type usually requires a permit and may need to be performed by licensed professionals, significantly increasing the cost of replacing a water heater.
Water Heater Location
The location of a mobile home water heater is especially important if it is a gas unit. A water heater located inside a mobile home, such as in a closet or alcove with no outside access, must be a sealed-combustion unit so that there is no connection between the heater's intake and exhaust and the home's ambient air. A gas water heater that is located in an exterior compartment—with an access door only on the outside of the home—can be a standard gas water heater that is approved for mobile home use.
Before You Begin
Close the shutoff valve on the cold water supply line feeding the water heater. Turn off the gas valve on the water heater's gas control unit, then close the shutoff valve on the gas supply line feeding the heater. Let the water heater cool completely.
Equipment / Tools
- Garden hose
- Adjustable wrenches, pipe wrenches, or tongue-and-groove pliers
- Drill and attachments for driving screws or anchors
- Drip pan and drain (as needed)
- New water heater of appropriate size
- Fasteners for tank brackets or strapping (as needed)
- Sheet metal screw
- Discharge tube for TPR valve (as needed)
- Thread-seal tape for plumbing connections
- Gas-rated thread-seal tape for gas connections
- Gas-leak testing solution
Drain the Tank
Attach a garden hose to the drain valve on the water heater tank. Extend the hose to a suitable drainage point, such as a landscape drain or a planted area. Open the drain valve completely to drain the water from the tank. Also, open the temperature-and-pressure relief (TPR) valve on the water heater to allow air into the system and prevent suction. When the tank is empty, close the drain valve and disconnect the garden hose.
Remove the Old Water Heater
Disconnect the flexible gas line from the gas control valve. Disconnect the hot and cold water lines from the tank outlet and inlet, respectively. Then, disconnect the vent duct from the draft hood on the tank. Remove all strapping or bracket fasteners securing the tank to the home's structure. Remove the tank from the water heater compartment.
Install a Drip Pan
Install a corrosion-resistant drip pan and drain for the new water heater, if necessary. You can reuse an existing pan if it is in good condition and is appropriately sized for the new heater.
Add the TPR Valve
Install the new temperature-and-pressure relief (TPR) valve onto the new water heater, following the manufacturer's directions.
Place the New Water Heater
Fit the new water heater into place on the drip pan. Position the heater so it is properly aligned with the existing gas supply, water piping, and vent duct. Secure the heater tank to the wall and floor, as applicable, using the brackets or strapping provided by the heater manufacturer. Be sure to follow local code requirements.
Complete the Vent Connection
Install the provided draft hood onto the new heater tank, as directed by the manufacturer. Typically, the hood snaps into place with a few tabs and may include screws. Fit the vent duct over the outlet on the draft hood, and secure the vent to the draft hood with a sheet metal screw.
Add a TPR Discharge Tube
Install a copper or CPVC pipe onto the TPR valve so the pipe drains to the home's exterior. You can reuse the old discharge tube if it is a suitable material, in good condition, and an appropriate size for the new TRP valve.
Connect the Water Lines
Connect the cold water supply pipe to the cold water inlet on the heater tank, using an approved supply connector and thread-seal tape for plumbing connections. Connect the hot water outlet on the tank to the hot water piping with an approved connector.
Make and Test the Gas Connection
Connect the gas supply tube to the gas control valve on the water heater as directed by the manufacturer, using gas-rated thread-seal tape. Turn on the gas supply to the water heater, and test all gas connections with a gas-leak testing solution to confirm there is no leaking.
Fill the Tank
Confirm that the drain valve on the heater tank is closed. Turn on the cold water supply to begin filling the tank. Open the hot water tap at the nearest faucet in the house. Let the tank fill until water flows at full force out of the hot water tap (indicating the tank is full), then close the faucet tap.
Check the Installation and Start the Tank
Confirm that all connections are secure and there are no water or gas leaks. Start the pilot light on the heater following the manufacturer's directions.