Oct 24th 2026
RV Water Heater Replacement Guide: 6 vs 10 Gallon, Suburban vs Atwood/Dometic Sizes
BUYING GUIDE · REPLACEMENT
RV Water Heater Replacement Guide: 6 vs 10 Gallon, Suburban vs Atwood/Dometic Sizes
Replacing a whole water heater? The opening in your sidewall decides what fits. Here are the real cutout sizes, recovery rates, and what changes when you switch brands.
The short version
- Same brand, same size is the easy swap: a Suburban 6 into a Suburban 6 opening (12-3/4 in. square), or a 10/12/16 into 16-3/8 in. square.
- Old Atwood 6-gallon → Suburban: the openings differ (Atwood is about 12-5/8 × 16-1/4 in.). Suburban’s SAW6 Direct-Fit is made for that swap.
- 6 → 10 gallon means cutting the sidewall bigger (about 3-5/8 in. each way on a Suburban) and about 1-1/4 in. more depth.
- Suburban recovers about 10 gal/hr on gas, 6 on electric, 16 with both.
Suburban sizes
| Gallons | Cutout (H × W × D, in.) | Gas input |
|---|---|---|
| 4 | 12.75 × 12.75 × 16.125 | 9,000 BTU/h |
| 6 | 12.75 × 12.75 × 19.19 | 12,000 BTU/h |
| 10 | 16.38 × 16.38 × 20.50 | 12,000 BTU/h |
| 12 | 16.38 × 16.38 × 22.25 | 12,000 BTU/h |
| 16 | 16.38 × 16.38 × 27.00 | 12,000 BTU/h |
From Suburban’s current spec sheet. Recovery for 6–16 gal: 10.1 GPH gas, 6.1 GPH electric (1440 W), 16.2 GPH both. Suburban tanks are porcelain-lined steel with an anode.
Atwood / Dometic sizes
| Model | Cutout (H × W × D, in.) |
|---|---|
| Older Atwood 4–6 gal (G6A, GC6AA) | 12-5/8 × 16-1/4 × 17-5/8 |
| Older Atwood 10 gal (GC10A) | 15-3/4 × 16-1/4 × 20-5/8 |
| Dometic WH-6GA / WH-6GEA | 12.9 × 12.9 × 19.5 |
| Dometic WH-9GEA | 12.9 × 12.9 × 24 |
| Dometic WH-10GEA | 15.8 × 16.3 × 20.6 |
| Dometic WH-16GEA | 15.8 × 16.3 × 25.1 |
From Atwood and Dometic installation manuals. Aluminum tanks, no anode. Dometic doesn’t publish recovery rates in its manuals.
Common swaps
| From | To | What it takes |
|---|---|---|
| Suburban 6 | Suburban 6 (SW6D/DE/DEL) | Direct swap in the 12-3/4 in. opening |
| Suburban 10 | Suburban 12 or 16 | Same 16-3/8 in. opening; needs about 1-3/4 in. (12) or 6-1/2 in. (16) more depth |
| Old Atwood 6 | Suburban SAW6 Direct-Fit | Suburban says no sidewall changes, using existing plumbing |
| Old Atwood 6 | Dometic WH-6GEA | Dometic’s 6-gallon door conversion kit covers the different opening |
| Atwood 10 | Suburban 10 | Enlarge the opening about 5/8 in. in height (and about 1/8 in. width) |
| Suburban 6 | Suburban 10 | Cut the sidewall to 16-3/8 in. square and allow about 1.3 in. more depth |
| Tank | Tankless | Suburban sells tankless panels for Suburban and Atwood-style openings; ST-42/60 fit a standard 6-gallon cutout |
Sizes calculated from manufacturer figures. Gas and water connection positions differ between brands; plan for plumbing changes on anything but a direct fit.
Picking features
- D (gas only) vs DE (gas + electric): electric lets you use campground power and recover faster with both on.
- DEL: lets you switch the electric from inside.
- 6 vs 10 gallon: with both heat sources a Suburban recovers about 16 gallons an hour, so a 6 is fine for many couples; families who shower back to back benefit from 10.
- Doors: sold separately and sized by opening; order one that matches your heater and opening.
Parts for this repair
Suburban SW6D 6 Gallon Water Heater (5238A)View part →
Suburban SW6DEL 6 Gallon Gas/Electric (5240A)View part →
Suburban SW10D 10 Gallon Water Heater (5242A)View part →
Suburban SW10DE 10 Gallon Gas/Electric (5243A)View part →
Dometic 94946 Access Door Conversion Kit, 6 GallonView part →Shop by category: New RV water heaters, 6 gallon water heaters, 10 gallon water heaters, Suburban water heaters, Tankless water heaters.
FAQ
Can I replace an Atwood water heater with a Suburban?
Yes. For older Atwood 6-gallon units, Suburban’s SAW6 Direct-Fit is designed to fit without sidewall changes. A standard Suburban needs a different opening size.
What size hole does a Suburban 6 gallon water heater need?
12-3/4 in. square and about 19-3/16 in. deep.
What size hole does a Suburban 10 gallon need?
16-3/8 in. square and 20-1/2 in. deep.
Can I upgrade from a 6 to a 10 gallon water heater?
Yes, but you’ll need to enlarge the sidewall opening and have enough depth (about 1-1/4 in. more on a Suburban).
Not sure which part fits? Contact us with your model and serial number from the data plate and we’ll confirm it before you order.
From Suburban’s spec sheet, 2025 catalog and Direct-Fit page, and Atwood/Dometic installation manuals. Swap clearances are our calculations.