Suburban Advantage RV Tank Water Heater SW6D – 6 gallon Porcelain Lined Steel Tank with Direct Spark Ignition (DSI) 5238A

Why I swapped in the Suburban 6‑gallon DSI heater

I replaced an aging RV water heater with Suburban’s 6‑gallon DSI model to get something serviceable, efficient on propane, and flexible enough to run on campsite power. I travel year‑round, and I value systems that are simple to maintain in the field. This unit’s porcelain‑lined steel tank with a replaceable anode rod checked those boxes, and the ability to add a 120V, 1,440W electric element meant I could save propane when I’m plugged in.

What I installed and how it fits

The Suburban 6‑gallon DSI heater is a traditional tank design with a 12,000 BTU gas burner and direct spark ignition. Its flue‑tube heat transfer design slows combustion through the core, which improves heat transfer into the water. It’s a compact box—12.69 x 12.69 x 19.19 inches—with a cutout spec of 12.75 x 12.75 x 19.19. In my coach, the opening needed slight trimming on one side to match the taller flange, and I reused the existing door after adding a new trim ring. Plan on sourcing the exterior door/trim kit if your old one won’t align; it’s not included with the heater.

Plumbing is 1/2‑inch NPT on hot and cold. I used brass adapters to transition to PEX, applied a potable‑water thread sealant (paste, not tape), and pressure‑tested for leaks before buttoning up. The T&P relief valve comes preinstalled and points downward at a safe angle. Electrically, the 12V control harness connects to the coach harness for DSI ignition and fault/enable signals. For shore‑power heating, you’ll need to wire the optional 120V element to a dedicated breaker. I chose a switchable outlet so I could lock out the electric element when the microwave is in use; at 1,440W it pulls roughly 12A.

One install gripe: the 12V pigtails are short. I added 6‑inch extensions with heat‑shrink butt splices to make final connections without skinning my knuckles inside the cutout. Also, the chassis doesn’t provide recessed mounting holes; aligning the door and securing the unit would be simpler if those were standard.

For sealing the exterior, I bedded the flange in butyl tape and finished with lap sealant after the door went on. That’s been watertight through a couple of stormy weekends.

Heating performance in real use

On propane only, heat‑up is quick. From a cold fill, I saw stable, scald‑ready hot water (around 130°F) in roughly 15 minutes. Suburban rates recovery at 10.1 GPH on gas and 6.1 GPH on electric; that tracks with how it behaves at the tap. On electric only, it’s a quiet, steady warm‑up—good for dishes and short showers if you’re patient. Where this heater shines is combined mode: propane plus electric easily supports a long shower or back‑to‑back showers without the temperature roller coaster you get with smaller burners.

The burner is well‑mannered. Ignition is quick, the flame stays stable, and the exhaust note is more of a low whoosh than a roar. Wind hasn’t caused nuisance flame‑outs for me, though as with any side‑vented RV heater, proper exterior door fit matters.

Standby losses are modest for a 6‑gallon tank. After heating to temperature and shutting both modes off, I could still rinse dishes hours later with acceptably warm water. Insulation seems up to par for a steel tank unit.

Build and serviceability

The porcelain‑lined steel tank is a clear benefit if you plan to keep your rig a long time. Steel plus a sacrificial anode has proven durability, and it’s easy to service. The anode rod doubles as the drain plug; a 1‑1/16‑inch socket and a short extension live in my toolbox specifically for this. The first removal after initial heat cycles took some muscle—I used a small breaker bar to crack it free—after that, normal torque has been fine. I flush the tank while the plug is out, and sediment purge is straightforward.

The control board and gas valve are accessible behind the exterior door. I appreciate that I can test DSI ignition and check fault lights without pulling the whole unit. The flue tube is protected inside the shell; there’s no special maintenance beyond keeping the exterior vent clear.

Winterization is easy with a bypass kit. I drain via the anode rod, open the T&P briefly to vent, and then run antifreeze through the bypassed lines. Come spring, I reinstall a fresh anode if it’s more than 50% consumed and I’m done.

Using propane versus electric

• Electric (1,440W): Silent, clean, and perfect for shore power or when the generator is already running. Heat‑up is slower, but for dishes and routine hand‑washing it’s convenient and thriftier than burning propane.
• Propane (12,000 BTU): Quick recovery and resilient in cold weather. I use this for showers and when I’m boondocking.
• Combined: Best of both worlds for back‑to‑back showers; the tank rarely dips below a comfortable temperature.

If your rig is on a 30A pedestal, it’s smart to manage loads. I wired a dedicated switch for the electric element so I don’t pop a breaker when the microwave or A/C cycles.

What I’d change

• Include the door/trim or at least make the mounting interface more universal. Sourcing the right door adds time and cost.
• Provide longer 12V leads. Six more inches would save a lot of fumbling.
• Factory torque on the anode plug can be excessive from new. A dab of proper thread sealant and a sensible torque spec would help first‑service removal.
• Add recessed or clearly marked chassis mounting holes to improve alignment and anchoring without relying solely on the door frame.

I also saw a minor weep from the T&P valve after the first two heat cycles. Introducing an air pocket at the top of the tank (open a hot tap while filling, then close the T&P gently) resolved it. If yours still dribbles, replace the valve—it’s an inexpensive part and easy to access.

Tips from the install bench

• Upgrade to brass plumbing adapters; they seal better and survive vibration.
• Use butyl tape under the exterior flange and finish with lap sealant for a watertight seal.
• Add 12V pigtail extensions before sliding the heater fully into the opening.
• Pre‑fit the exterior door to confirm hinge and latch alignment before final fasteners go in.
• Keep a 1‑1/16‑inch socket in your kit for the anode/drain. Flush the tank at least once a season.
• If you add the electric element, give it a dedicated breaker or switched outlet and label it clearly at the panel.

Who this heater suits—and who it doesn’t

If you want a durable, serviceable RV water heater that behaves like a small residential tank, this Suburban is a strong choice. The porcelain‑lined steel tank and sacrificial anode make long‑term ownership economical, and the gas/electric flexibility is genuinely useful. If you prefer endless hot water or minimal standby loss, an on‑demand unit may fit your style better—but be ready to manage flow rates, inlet water temperature, and higher power demands.

Warranty and support

Suburban backs the unit with a 2‑year limited warranty and a 3‑year limited tank warranty. That aligns with the build philosophy here: the tank is the heart of the system, and the parts most likely to need service (anode, T&P valve, control board) are accessible and reasonably priced.

Bottom line

I recommend the Suburban 6‑gallon DSI water heater. It heats fast on propane, sips shore power on electric, and it’s built in a way that rewards routine maintenance. The small hassles—short 12V leads, sourcing the exterior door, and the initial anode torque—are one‑time problems. Day‑to‑day, it’s quiet, reliable, and easy to live with. If you value predictable hot water and long‑term serviceability in a compact RV package, this is a smart upgrade.