Thursday, June 8, 2023


Can I sanitize RV’s fresh water tank without running solution through water lines?

Dear Dave,
My coach is fully winterized as I flushed the pink, nontoxic, antifreeze through all lines, and the fresh water tank has been drained. I am about to dewinterize the coach and I will want to sanitize, with a bleach solution, the fresh water system. Given that there has been antifreeze in the lines for several months, do I still need to run the bleach solution in all the pipes? It sure would be easier if I only had to allow the bleach solution to sit in the fresh water tank, drain it after a few hours, and not flush the bleach solution through the pipes. Thank you for your advice and for what you do! —Philip, 2022 Newmar Dutch Star 4081

Dear Philip,
You can just flush the fresh water tank out with a bleach solution to sanitize it. They recommend 1 tablespoon for every 1 gallon of water for smaller tanks, and 1 cup for 50 gallon tanks. If you have a 100-gallon tank, most owner’s don’t fill all 100 gallons, but rather use the 50-gallon method and drive around for a while to get everything coated. If you want to fill it up, use 2 cups bleach. This will sanitize and freshen it, and if you don’t want to run it through all the lines, you can just dump the fresh water tank at the dump valve.

Flush antifreeze out of lines

However, you will still have the pink antifreeze in all the lines and will want to flush that out until they are filled with fresh water.

Why not do this while you have the fresh water tank full of the diluted bleach and water solution, unless you don’t want the bleach smell/taste in the water lines? I guess you can dump the diluted bleach solution from the fresh water tank, fill the tank with fresh water, and then flush the pink antifreeze out of all the lines. However, I believe you will still get some of the bleach taste from what was in the fresh water tank. The pink antifreeze has a sugar content and even though it is odorless and tasteless, it is a little slippery or greasy like, and you will want to flush it all out.

Another option

Another option would be to use the Thetford Fresh Water Tank Sanitizer product. This has no bleach smell/taste.

This two-part system will help sanitize and deodorize the fresh water tank and all the lines. So you could use it instead of the bleach and then flush the water lines out, saving a step.

 You might also enjoy this from Dave 

How do I sanitize my RV’s fresh water tank through the filter?

Dear Dave,
I want to disinfect the RV’s fresh water tank after the long winter storage. Even though it has been “empty,” I will be adding some bleach along with water. To fill the tank, one must use a hose. I would like to remove the disposable water filter installed by Newmar in the wet bay and add some bleach/water to the filter holder and screw it back in without the filter and flush the mixture into the freshwater tank. Will this work or is there a better way? If I left the filter in and added bleach via a hose, I suspect the activated charcoal filter would remove the bleach before it went into the tank. I am assuming the filter is between the hose fill and the tank. Your thoughts? Thanks. —Phillip, 2022 Newmar Dutch Star 4081
[Yes, this is the same person whose question Dave answered above.]

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


We have a popular forum for Ask Dave. Please be as brief as possible. Attach a photo or two if it might help Dave with his response. Click to visit Dave’s forum. Or send your inquiries to him using the form below.

Click or drag a file to this area to upload.


Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


4.3 4 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Deborah Mason
2 months ago

Absolutely want that pink stuff out. It may claim tasteless, but it has a nasty taste to at least one or two people. A couple years ago we had some residual & it took a while before we could tolerate our own water.

2 months ago

I’ve been RVing for 15 years and I’ve found the simplest solution to sanitizing my fresh water tank is to: I have an 85 gallon tank and I use a chemical called Chlor Brite by a swimming pool company. It’s ingredient’s is Sodium dichloro-s-triazinetrione dihydrate. (mouthful) It’s in a glandular form. I fill my tank to about 60 gallons and it just takes 1 tablespoon of this to sanitize my tank. then I drive around for 5 mins. Then I turn on my water pump and run water through each line in the RV. This sanitizes everything including my water filter and water pump. Then I drain my tank and refill and drain again. But I don’t drink water from my water tank. I carry gallons of distilled water with me and buy more as needed from grocery stores along the way.

Bob Palin
2 months ago

If the tank needs to be sanitized after having the pink stuff in it why wouldn’t the lines also need sanitizing?

2 months ago
Reply to  Bob Palin

Good point. That’s why we put bleach/water in the fresh water tank after all the pink is gone and run it through everything, flush it and run straight water through all of it again.

2 months ago
Reply to  Dan

That’s the way we do it also, but run clear water through the lines before sanitizing to remove the A/F Also, don’t forget to purge the city water fill (hopefully you did this when pumping the anti-freeze). Depending on how long the line is, you may have up to 1/2 gallon of anti-freeze in that line. Flush the tank and lines til you don’t smell bleach, then do it again to be sure.
If there is a small amount of bleach left, you won’t notice it. If any A/F is left you will.

2 months ago
Reply to  Bob Palin

When we winterize, the fresh water tank is emptied, and not filled with antifreeze. RV antifreeze is pumped through the rest of the lines (hot water tank on by-pass) via the intake for that on the pump.
While tempting, I think we’ll do the usual flush/sanitize the entire system/flush instead of just sanitizing the tank.

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.