Can I just drain my on-demand water heater, or does it need RV antifreeze?

Dear Dave,
If I drain all water lines at low points and blow out all the lines and open the pressure drain valve, do I have to add RV antifreeze to the Truma Combi boiler? Thanks in advance. —John, 2023 Thor Tellaro

Dear John,
According to the Truma service video and manual, you do not need to use RV antifreeze to winterize your Truma Combi furnace and water heating system. As you mentioned, you need to drain the water lines at the low point drain locations as well as blowing out the lines. To blow out the lines, they recommend using compressed air set at approximately 40 psi to assure all water lines and compartments are free of any standing water. Here is their procedure:

Winterizing your Truma Combi

The Truma Combi’s water container must be drained to avoid damage whenever there is a risk of frost while your RV is not in use. After draining the water, the Combi furnace is protected against freezing conditions.

Step 1: Begin by turning off the Truma Combi and give the unit time to cool down. Place a vessel that’s at least 2.64 gallons (10 liters) underneath the drainage outlet of the drain valve, to catch the drained water. Make sure all of the water drains from the Combi.

Step 2: Use the main switch or pump switch to switch off the power to the water pump.

Step 3: Turn off or disconnect the city water connection, if present.

Step 4: Open all water release points, e.g., cold and hot water faucets, showers, toilets. The unit should be placed in bypass in accordance with the manufacturer’s instructions.

Step 5: Flip yellow handle “up” to be in line with valve body to drain. The water container will drain via the drainage outlet of the drain valve. Leave the drain valve open for the winter season. Make sure all of the water drains from the Combi. If the water does not drain, check the clear tube for obstructions. (Call Truma Service if you need assistance at 1-855-558-7862 ext. 1.)

Does this work for all on-demand systems?

No, the Girard System owned by Lippert requires RV antifreeze to be added to it’s chamber as not all compartments will be drained, even with compressed air.

Aqua-Hot

Aqua Hot recommends draining the water and flushing with RV antifreeze.

Please follow these instructions carefully when winterizing the Aqua-Hot’s water heating system:

1. Completely drain the freshwater storage tank.

2. Disconnect the domestic water demand pump’s suction line from the freshwater storage tank.

3. Attach an adequate piece of hose onto the suction side of the domestic water pump.

4. Place the opposite end of the hose into an adequate supply of FDA-approved “GRAS” RV Antifreeze and turn on the demand water pump. (“GRAS” stands for “Generally Regarded as Safe.” This is the “Pink Stuff”.)

5. Open and close all interior and exterior water faucets, one at a time, until ONLY pure RV antifreeze is present. Perform this procedure for both hot and cold faucets.

6. Remove the hose from the RV antifreeze and reconnect the domestic water demand pump’s suction line to the freshwater storage tank.

Make sure you consult your on-demand system owner’s manual or customer service representative for winterizing requirements for your make and model.

 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. 

##RVDT2238