HUD Approved Water Heaters for Mobile Homes, and How to Check One
The short version
- HUD runs no approval list for appliances. The maker certifies, and A. O. Smith and State print the line HUD compliant, approved for mobile homes/manufactured housing.
- The binding sentence is 24 CFR 3280.709(a): every appliance must be installed to the terms of its own listing, which a site built tank has none for.
- Thirty gallon nominal gas bodies hold 29 by the spec table and measure 18 inches across, so the compartment, not the label, caps any upsize.
- Direct vent burns 30,000 BTU at that size, atmospheric 35,500, propane 29,000. One box, converted in the field.
- HomeGuide's 2026 pricing puts a 30 gallon swap at $500-$1,900 installed, plus $125-$300 per labor hour where access is cramped.
No tank carries a HUD approval stamp. A HUD approved mobile home water heater is one the maker certifies for manufactured housing, and the proof is printed on its spec sheet: A. O. Smith and State use the line "HUD compliant, approved for mobile homes/manufactured housing".
Rheem pairs NAECA with HUD certification for manufactured housing; Richmond covers manufactured (HUD) and modular construction. Three wordings, one claim.
Haverlane is a publication, not a contractor. Dialing (800) 555-0176 puts a licensed plumbing partner on the line, and work that follows can pay Haverlane a referral fee that never touches your quote.
The code says listed, and never says approved
Search the code for a heater HUD has approved and nothing turns up. The duty sits on the fixtures instead: a dwelling unit with a kitchen sink and a tub or shower must be supplied with hot water, from a heater that carries a listing (24 CFR 3280.609(a)(2)). Listed is the operative word. No brand, no capacity, no model number.
Enforcement waits one subpart over. Under 24 CFR 3280.709(a) an appliance may go in only the way its own listing and its manufacturer's instructions set out, and nothing outside those two documents is a compliant installation. Apply that to a tank listed for site built houses: its listing says nothing of a manufactured dwelling, so there are no terms to install it by. That absence is what owners call approval, and it drives every physical difference between the two appliances.
Four checks before you pay for a tank
Partner plumbers run these four before a HUD approved mobile home water heater goes on the truck.
- Read the printed claim. Manufactured housing wording belongs on the product page, the spec sheet and the manual. A. O. Smith's direct vent manual, part no. 315795-000, puts FOR USE ONLY IN MANUFACTURED HOMES on its cover.
- Match the vent to the compartment. Two routes satisfy 3280.709(d) and there is no third: the appliance is sealed combustion, or its enclosure is closed to the living space, with no door, no removable access panel, no unsealed opening.
- Measure first. That same manual draws the box the tank must fit: nothing at the sides or back, 4 inches from the jacket front to the closet door, 27 inches of clear air above the jacket to combustible material. Its gas bodies run 18 inches across at 30 gallons, 20 at 40 and 22 at 50.
- Check the safety fittings. The corrosion resistant drip pan under the tank is federal, at 3280.709(h). So is the relief valve's route out: full size pipe to the exterior, never terminating under the home, ending 6 to 24 inches above finished grade, untrapped, its end left visible for inspection.
Reading and measuring are yours. Hanging the unit is the licensed half: vent, fuel line and relief piping are all inspectable work.
Why the 30 gallon mobile home water heater is the default size
Thirty is the capacity these closets were framed around, and where the marketing number and the spec table part company. Every 30 gallon nominal gas body from A. O. Smith, State and Reliance lists rated storage of 29 gallons, and the electric lowboys hold less again.
| Model | Fuel | Nominal / rated gal | Input | First hour, gal | Diameter |
|---|---|---|---|---|---|
| ProLine FMDV-30 250 | Gas, direct vent | 30 / 29 | 30,000 BTU | 60 | 18 in. |
| ProLine FMHR-30 400 | Gas, atmospheric | 30 / 29 | 35,500 BTU | 63 | 18 in. |
| Reliance 6-30-DHMTK | Electric | 30 / 27 | 120 V, 3,000 W | 50 | 19 in. |
| ProLine EMHL-30 | Electric lowboy | 28 / 26 | 120 V, 3,000 W | 47 | 22 in. |
Sourcing note: the ProLine bodies above are A. O. Smith, whose corporate family also owns Reliance and State, and Richmond is a Rheem brand. Four agreeing spec sheets are two voices.
A mobile home 30 gallon gas water heater, natural or propane
Direct vent bodies draw 30,000 BTU at 30 gallons, 32,000 at 40 and 40,000 at 50 on natural gas, per the 2026 Reliance spec sheet. Atmospheric bodies run 35,500 BTU at both 30 and 40 gallons, which is why the smaller one posts the higher first hour rating of that pair, 63 gallons against 59.
Propane changes little. A. O. Smith ships every model set for natural gas and supplies a propane burner for the conversion, and Richmond calls its controls field convertible. Inputs drop to 29,000 BTU on the direct vent bodies, and Reliance notes propane may reduce first hour rating and recovery.
Altitude is brand specific: Reliance approves standard vent models to 10,100 feet and direct vent to 5,400; Richmond certifies its line to 10,000. Check before ordering if the lot sits high. Fuel choice gets fuller treatment on the gas tank page.
Talk it through with a mobile home plumber
Call (800) 555-0176Free to dial. You reach a licensed plumber who works on manufactured homes.Partner plumbers who service manufactured homes- Plumbers who actually work on manufactured homes
- Line answered day and night, all year
- Dialing costs you nothing
- Price talk happens between you and the plumber
The electric side: 120 volts and elements you cannot swap blind
Electric units here answer to no special standard: part 3280 points storage tanks at UL 174, the ordinary household one. What suits a model to a manufactured dwelling is its shape, its side connections and its label.
Wattage is the part owners feel in the shower. Richmond puts recovery at 17 gallons an hour on 3,500 watts and 21 on 4,500 at a 90 degree F rise, while Reliance still sells 1,500 watt single element bodies on 120 volts. Reliance also builds a 3,800 watt model, so a generic 4,500 watt element off a shelf can overrun the circuit that tank was wired for.
An electric 40 gallon hot water heater for mobile home use is the ceiling of the range; no 50 gallon electric model appears in these catalogues, and the 40 gallon electric page works through that size. Pulling an element is still owner work, on two conditions: breaker off first, tank drained second. Everything upstream of the junction box belongs to a licensed trade.
HUD compliant does not mean welcome in your closet
On its gas pages for this market Reliance stars a claim of meeting HUD requirements for manufactured housing and mobile home installation. The asterisk then leads to a footnote ruling that unit out of inside closets where the design has to be direct vent. A HUD approved mobile home water heater can still be the wrong appliance for your compartment.
That compartment carries rules of its own. Carpet is kept out from under a furnace or a tank by 3280.205, and no door or drape may swing closer to the appliance front than its labeled clearances. A space not framed in or guarded with noncombustible material has to wear a 3 by 5 inch adhesive backed laminated label, its warning being that the compartment is no place for storage. Go look for it; on plenty of these homes it is still stuck to the panel.
Where your own place keeps the paperwork
Two documents settle what you own. One is metal and hangs outside: the certification label, the HUD tag, roughly 2 by 4 inches, riveted about a foot up from the floor at the taillight end of every transportable section. A double section wears two of them.
The other is paper and lives indoors: the data plate, one sheet of ordinary letter size paper. HUD sends owners to three places to hunt for it, the electrical panel, a kitchen cabinet, a bedroom closet. It names the factory installed equipment, which is where the original tank appears. Census counts this housing in a category that also holds boats and RVs, and about two thirds of it was built before 2000, so that first unit is usually long gone and what counts is the certification on its replacement.
What a certified swap actually costs
HomeGuide's 2026 national figures put a 30 gallon unit at $300-$900 and $500-$1,900 installed, on 2 to 6 hours of plumber time for a same size exchange. Then the extras peculiar to this housing: the roof jack kit is a separate order sized to vent length, vent replacement $100-$600, a dedicated circuit $250-$900, permits $50-$200.
One HomeGuide line reads as though written for this niche: reaching into a cramped closet adds $125 to $300 for every extra labor hour. The bands cover every housing type, and the certified catalogue here is narrower, so read the bottom of each range as optimistic. The step by step swap shows where the hours go.
Where reading stops and dialing starts
Measure the closet, photograph the rating plate, find the data plate, price the unit: all yours. Stop at the fuel valve, the vent, the roof jack and any 240 volt circuit, because those are licensed trades and the parts an inspector reads first.
Dialing (800) 555-0176 costs nothing and reaches a plumber licensed for this work, at any hour. Have the data plate, the fuel and the closet width ready, and the call gets short fast.