My on-demand water heater has no bypass or drain. Can I use RV antifreeze in it?

Dear Dave, 
I have an Intertek tankless water heater on my 5th wheel camper. We live in the Midwest and have very cold winters. There is no place to drain what little water is in it and no bypass valve either. Is it all right to run RV antifreeze through it? —Dave, 2023 Keystone Cougar 23MLE

Dear Dave,
I can tell it’s getting cold, as the winterizing questions are falling into my inbox like the leaves outside! Intertek is actually a testing/certification company and not the brand of water heater. I ran a company for the past 10 years that made an industrial pressure washer for the fast-food industry. We had to send a unit to Edison Test Labs (ETL) and have it destroyed in every way possible to ensure employee safety, then have it inspected every quarter to ensure no parts were changed or, if they were, they needed to be recertified. I assume this is the same for the on-demand water heater you have.

According to the Keystone website, your unit has a Girard on-demand water heater, which is owned by Lippert. It does not specify the model; however, it is either a GSWH-1 or GSWH-2. Both have the same winterizing recommendation. And you are correct—there is no bypass or drain valve.

First step to winterize on-demand water heater

The first step would be to empty the freshwater tank and then find the low point drains, typically underneath and behind the driver side tire. Remove the plugs and open all the faucets, including the shower, and flush the toilet. According to the Girard Owner’s Manual, you can either blow the lines out with compressed air, dialing it down to 35 psi, or run RV antifreeze through the system.

However, according to the Lippert tutorial on winterizing the Girard unit, you cannot get all the water out of the on-demand unit using the compressed air method. They recommend using compressed air to drain everything else out and then adding non-toxic RV antifreeze into the system. Your unit should have a winterizing kit or valve that allows you to use the on-board water pump to draw the pink stuff in and through the system. Check your service center for the lever or valve.

With the lever to the “off” position, the pump will draw water from the fresh water tank. In the “on” position, it will switch and draw from either the attached hose or, in this case, the “Freeze Guard” inlet in which you hook a draw hose to it. Either way, you put the other end of the hose into the RV antifreeze and turn on the pump.

Next steps

With the pump on, it will draw RV antifreeze through the line until it is pressurized and stop. Go inside and open a cold water line until you see the pink stuff flowing. This will indicate the incoming line and pump now has RV antifreeze in it. Then open the farthest hot water faucet until RV antifreeze comes out.

If you blew the entire system out with compressed air, this is the only line you will need to add the antifreeze to, as all the other lines are empty. So, you don’t need the 3-5 gallons used when doing all the lines. Otherwise, you would need to do the entire water system. Don’t forget the exterior shower, ice maker, and black water flush valve/line.

 You might also enjoy this from Dave 

How do I keep my RV’s on-demand water heater from freezing?

Dear Dave,
Grand Design installed a Furrion 2.4 gpm tankless water heater in the Reflection. I did some research on this heater, and the heater manual recommends not using it below 39 degrees F. Well, that is almost impossible in Oregon. My dealer was not aware of this. Bottomline is the heater froze and looks like it’s toast, per mobile repair tech. Question is, do you know if Furrion has done anything to address this issue? I’m probably due a new heater, and dealer has recommended apples to apples for replacement. Thanks. —Steve L., 2021 Reflection 303RLS

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here. 

##RVDT2511