Mobile home water heaters look identical to standard residential models from the outside — but the install requirements and certification matter. You can\'t just install any water heater in a manufactured (mobile) home — HUD code requires specific certified models. This page covers the requirements, the models that fit, and the installation rules unique to manufactured housing.
HUD code — the underlying rule
Manufactured homes (homes built to HUD Manufactured Home Construction and Safety Standards, aka HUD code) are regulated differently from site-built homes. For water heaters, HUD code requires:
- Mobile-home-certified model — the unit must be tested and labeled for manufactured housing use
- Sealed combustion for gas units — combustion air comes from outside, not from inside the home. Direct-vent two-pipe configuration
- Specific anchoring — water heater must be physically secured (strap or bracket) to prevent movement during transport
- External access in many configurations — for safe maintenance and to meet HUD ventilation requirements
- Specific venting termination clearances — different from site-built homes due to the lower roof profile
Why mobile homes are different
Three structural reasons:
- Tight envelope — manufactured homes have less air infiltration than site-built homes. Atmospheric (open-combustion) gas appliances can cause CO buildup or depressurization issues
- Limited roof clearance — vent runs are shorter; venting must work at lower stack heights
- Movement during transport — even if the home is permanently sited, original transport stresses require anchoring
Mobile home certified models
Most major brands offer mobile-home-certified variants of their standard tank water heaters. They typically have an "MH" or "Mobile Home" suffix in the model number, or are sold as a separate SKU line.
- Rheem Mobile Home Series — gas tank water heaters in 30, 40, 50 gallon, sealed combustion direct vent. See Rheem lineup
- AO Smith Mobile Home / State Mobile Home Series — similar product range from AO Smith and State (their subsidiary brand). See AO Smith lineup
- Bradford White Mobile Home — sealed combustion variants of their standard lineup, sold only through plumbing wholesale
- Tankless options — most tankless units (Rinnai V-series, Navien NPN) are already sealed-combustion direct-vent and require only the certification check, not a model change
When buying, look for the HUD certification label on the data plate. If it's not there, the unit isn't certified for mobile home installation.
Sizing for manufactured homes
Manufactured homes tend to be smaller than median site-built homes and have fewer bathrooms — sizing skews smaller:
| Home configuration | Recommended size |
|---|---|
| Single-wide, 1 bathroom, 1-2 people | 30 gallon gas or 40 gallon electric |
| Single-wide, 1-2 bathrooms, 2-3 people | 40 gallon gas or 50 gallon electric |
| Double-wide, 2 bathrooms, 3-4 people | 40-50 gallon gas or 50-66 gallon electric |
| Triple-wide or large double-wide, 3 bathrooms | 50 gallon gas or 66 gallon electric, or tankless |
Tankless is increasingly common in newer manufactured homes — V53DeN outdoor units (Rinnai) eliminate venting requirements entirely on warm-climate installs.
Install requirements specific to mobile homes
- Anchor bracket — required by HUD. Most installs use a metal strap or bracket securing the unit to a structural wall stud or floor plate
- Drain pan with overflow — required because most mobile home water heaters are installed in closets above living space
- Sealed-combustion venting — for gas units. The vent kit terminates at the side of the home, not through the roof
- Service clearances — typically tighter than site-built homes. Verify your closet meets minimum dimensions
- Combustion air — most installs use the sealed combustion intake; some require additional ventilation
Cost considerations
Mobile home certified units typically cost 10-20% more than equivalent standard models — the sealed-combustion configuration is more complex. Installation labor is similar or slightly higher due to the more complex venting.
| Type | Mobile home certified, installed |
|---|---|
| 30-gal gas tank, mobile home | $1,200-1,800 |
| 40-gal gas tank, mobile home | $1,400-2,200 |
| 50-gal gas tank, mobile home | $1,500-2,400 |
| 40-gal electric tank, mobile home | $1,000-1,500 |
| 50-gal electric tank, mobile home | $1,100-1,700 |
| Outdoor tankless (V53DeN warm climate) | $1,800-2,800 |
Permits and inspection
Mobile home water heater replacements still require permits in most jurisdictions. The inspector verifies:
- HUD certification of the unit
- Anchor bracket installed
- Venting routed correctly (sealed combustion two-pipe)
- Pressure relief valve discharge routed to exterior
- Drain pan installed if above living space
What you can\'t do
- Install a non-mobile-home unit in a manufactured home — voids insurance, violates HUD code, fire/CO risk
- Convert an atmospheric venting setup to sealed combustion DIY — gas-line work + venting work both require permits and licensed plumber in most jurisdictions
- Skip the anchor bracket — HUD requirement; insurance issue if you don\'t
Finding a mobile home water heater installer
Not every plumber is experienced with mobile home installs. Ask:
- "Do you do mobile home water heater installs?"
- "Are you familiar with HUD certification requirements?"
- "Do you have experience with sealed-combustion venting?"
Mobile home dealerships and parks often have a recommended local plumber who does volume mobile home work — usually faster and cheaper than a general plumber learning your specific install.
Related guides
Bottom line
For manufactured home water heater replacement: buy only a mobile-home-certified model (look for the HUD label), use a plumber experienced with manufactured housing, install the anchor bracket, and pull the permit. Don\'t install a standard residential unit in a mobile home — it\'s a code violation and an insurance problem. Most major brands offer certified variants; pricing is 10-20% over equivalent standard models.