Thursday, December 8, 2022


OK to store RV antifreeze in unused fresh water tank?



gary-736Dear Gary,
We have a Fleetwood Regal Prowler. It is a seasonal unit, set up at a campground year around. We are hooked up to city water and so do not use the fresh water holding tank. Can I pour 12 or more gallons of RV antifreeze into the tank and use what I need to winterize the trailer each year from what I have stored in the fresh water tank? And an important question: Does the stored antifreeze remain stable or does it deteriorate? —Richard

Dear Richard,
I see no reason not to attempt what you are suggesting. As long as you never need on-board, self-contained fresh water, why not use the fresh water storage tank as an antifreeze holding container? RV antifreeze will have a shelf life, but I do not know how long it will actually stay viable, so check with the suppler to be sure of its life expectancy. I’m sure the producer of that brand will have what’s called an MSDS sheet that should help shed some light on its lifespan.

And I’m certain you would not require 12 gallons of it to properly protect your Prowler. I do recommend a water heater bypass kit to keep the antifreeze cost down though. I would venture you’d be able to safely use the same antifreeze for a minimum of at least two years. You can always test its effectiveness after that by using a coolant hydrometer. I’d run a little through the water pump as well to keep the gaskets and seals moist in there since you never use the pump while on city water. But, shoot … I’d say go for it since you employ city water all the time. If need be, it can always be flushed out later.

Editor: Shop for RV antifreeze at Amazon.

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.


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5 years ago

I’m with Rick on this one, the taste transfer, disclosure to an eventual buyer and the lack of a fresh water reserve are all good reasons not to go ahead with this idea.

5 years ago

Having had water systems previously go down in places we have stayed, I always appreciate keeping some fresh (and refreshed water) in the fresh water tank. One just never knows until too late.
If in the fresh water tank for any period of time, seems like it would taint that intended fresh water tank for a long time. Would you disclose to a buyer?
I know from my last 3 rigs, if pumping from the freshwater tank I cannot by-pass filling the hot water heater with a LOT of unneeded anti-freeze.
Good luck