The MRH series is Marathon\'s short-height variant — for mobile homes, crawl-space installs, and tight under-counter applications where standard-height tanks won\'t fit. Same composite tank technology and lifetime warranty as Standard MR; just wider and shorter to maintain capacity in a low-ceiling install.
The lineup
- MRH38 — 38-gallon Lowboy. Common mobile home replacement size
- MRH50 — 50-gallon Lowboy. Volume Lowboy pick for 3-4 person mobile homes
Form factor
| Model | Height | Diameter | Comparison |
|---|---|---|---|
| MRH38 (38-gal lowboy) | ~33" | ~22" | vs MR40 standard: ~52" tall, ~19" diameter |
| MRH50 (50-gal lowboy) | ~33" | ~24" | vs MR50 standard: ~60" tall, ~21" diameter |
Lowboys trade height for diameter — same capacity in a shorter (but wider) cylinder.
Common applications
- Mobile homes — primary application. Mobile home water heaters live in narrow closets with low ceiling clearance
- Crawl-space install — when tank must fit under a low floor
- Under-counter installs — kitchens or laundry rooms with cabinet constraints
- Basement install with low-clearance HVAC ductwork overhead
- Garage installs with low ceilings or storage above
Specs
- 240V dedicated 30A circuit
- 4500W upper + 4500W lower elements
- Same composite polybutylene + fiberglass tank construction
- Lifetime tank warranty (residential, original owner)
- 6-year parts warranty
- 0.93 UEF
- No anode rod required
Install considerations
- Larger diameter than standard tank — verify clearance at the install location
- Floor footprint larger than equivalent capacity standard tank
- Plumbing connections at top as usual
- Same 240V 30A circuit as standard residential
- Drain pan sized for the larger diameter footprint
Mobile home considerations
- HUD code mobile homes require water heaters rated for mobile home use — verify model is HUD-rated
- Mobile home water heater closets are typically 24" wide; verify before ordering
- Many mobile homes have undersized electrical service (100A or 125A); verify breaker capacity before replacing a non-electric tank with electric
Lowboy vs upgrade to standard
If you have ceiling clearance for a standard-height tank, choose Standard MR over Lowboy. Standard tanks have slightly better insulation and slightly better real-world efficiency due to the geometry. Lowboy is the form-factor accommodation, not a preference.
Cost comparison (50-gallon equivalent)
- Marathon MR50 standard: $1,299-1,599
- Marathon MRH50 Lowboy: $1,399-1,699 (small premium for the wider tank form)
Bottom line
Marathon Lowboy MRH series is the form-factor pick — for mobile homes, crawl spaces, and low-ceiling installs. Same composite tank technology and lifetime warranty as Standard MR. MRH50 is the volume Lowboy pick. Choose only when standard tank height won\'t fit the install location.