Dear Dave,
I can never get a straight answer, or I’m just not understanding the way they describe a water heater. I have a SW6D water heater that I would like to replace with a unit that I can run on 120 volt all the time. If you would, please give me some suggestions on which units are available. Thank you in advance. —Dennis, New Vision 5th wheel
Dear Dennis,
Your SW6D is a Suburban 6-gallon water heater that runs on propane only. The “D” stands for “direct spark,” which means you do not have to pre-light a pilot light.
You do have a few options, depending on your needs. Both Dometic and Suburban have a 6-gallon model that will run on either 120-volt power when plugged into shoreline power, or liquid propane (LP) with a flame. You did not provide the model year or floorplan of your RV. However, the water heater in your RV has not changed much for the past 30 years and would look similar to the one we are working on in this 1996 Forest River Salem. This is also a model SW6D and measures 14.4” wide x 14.5” tall. The flange is 1.25”, so the actual opening should be 12” x 12”.
If you are going to replace the current SW6D with a new model, you will need to verify the size of the opening in the sidewall and also the space inside that the tank is located. The opening is not as much of a concern, in my opinion, as you can get an adapter plate for a smaller unit or cut a larger hole for a bigger one. However, take a look at the tank sitting inside that might be an issue.
This is the tank of our SW6D sitting inside a bench seat in the rear. As you can see, there is ample room for anything longer. Plus, there is enough space for any customized plumbing that might be needed.
Options for an electric water heater replacement
You can replace the current SW6D with either a Dometic or Suburban 6-gallon electric or LP water heater that will be about the same size opening and depth. When operating on LP mode, they run just like your current unit, which uses a flame to heat the 6-gallon tank. When plugged into 120-volt power, the dual mode unit provides 120-volt power to a heating element inside the 6-gallon tank that heats the water.
If you are just going to use the 120-volt mode, the LP mode seems to be a waste of money. However, I do not know of anyone offering a single 120-volt mode replacement. It might be a good opportunity to upgrade to the dual mode version—just in case you do not have access to 120-volt power.
Winnebago uses a Suburban that has what we called “Motor Aid”. That is the engine coolant routed back to the water heater and an auxiliary heater in the back. As you drive, the engine coolant will get over 200 degrees and heats the water in the water heater tank and also provides heat to the back, just like the dash heater in front. This would also be a good option; however, it might be a little more than a DIY job to splice a coolant line and run it to the water heater and back.
Isotemp marine water heater
While I was researching the option of a 120-volt water heater, I came across a marine product that Panther RV Products had on their website. It is a 5.3-gallon water heater that has a 750-watt heating element that runs on 120-volt power, and also has the engine coolant option. You can find it here.
However, ranging from $675 – $1000 it would be better in my opinion to just upgrade to a SW6DE model that you can find for under $700.
You might also enjoy this from Dave
Can I leave the RV’s water heater on electric all the time when plugged into shore power?
Dear Dave,
My RV’s water heater uses both LP and electric. Can I leave the electric on all the time to heat water when connected to shore power? Thank you. —Ben, 2003 Monaco Knight
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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Hi Dave- Good response on the AC / LP combo, but I would add one more paragraph… Make sure you have room in your power center for another breaker and are comfortable with running AC power between the power center and the water heater. Plus, I personally would not put an AC water heater in a 30A rig that likely already has an air conditioner and microwave.
You learn fast just what you can run at the same time. We’ve learned to turn off the AC when using the microwave or coffee pot. I think I have turned on the heating element twice on my water heater. Just to see if it works. It takes a lot longer to heat the water on electric and it doesn’t recover near as fast. Trying to save on propane is not worth the inconvenience.
Hey Dave, too bad Dennis didn’t add his year & model as perhaps it was an option to have a gas & electric water heater! Who knows. Never say never when talking RV’s!
My $.02 cents
Snoopy
Another option for having an AC only water heater is to install an aftermarket heating element that installs in the drain plug fitting. They have complete kits for around $60. on Amazon. They are easy to install. They also are used to convert to dual fuel water heating.
Yep! The HottRod kit. I installed one in our propane-only Atwood 6 gallon tank and it works great. I haven’t filled my propane tank in over 2 years.
Only caveat is you have to be darn sure to unplug it if the tank is empty and you’re on shore power or generator.
I think it was about $100 on Amazon when I bought it. Can’t recommend it enough!
I just replaced the Dometic/Atwood water heater in my travel trailer after the tank cracked over the winter with a 4 gallon 120 volt only water heater. You have to be careful with the size versus the size of the compartment in your unit and that it will run on the 15 amp circuit supplied for the original heater but there are a number of them out there. The cost difference was huge, less than $200 vs well over $700 to replace the original. A quick search of ‘under sink water heater’ will bring them up.
A neglected issue is the heating capacity of the various sources of energy used.
Propane burner capacity is usually ~10kBTY/3.412kW.
OEM electric 120V heating elements are ~1.4kw.
Retrofit electric elements are ~.4kW.
These differences in capacity result in a much different heat-up time for a 6-gallon tank. Approximately 21.3 min for propane, 51min for OEM electric and 163 min for aftermarket electric. Be forewarned. If you keep it on all the time, it matters less but your ‘recovery’ time is much slower even if you keep it on.
Electrify Your RV Propane Water Heater: Yay or Nah? (doityourselfrv.com)
Thank you, Dave! 🙂 I am way out of my depth in this discusdion. Thank you for lowering the water level a bit. 🙂 Safe travels! 🙂