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How to Sanitize an RV Freshwater Tank

I am sharing how easy it is to sanitize an RV freshwater tank in this how-to article. I’ve shared a downloadable PDF of my checklist for sanitizing an RV freshwater tank. Why would you want to do this? Well, it is a great way to remove any mal-tasting water problems in your RV. It is not uncommon to find mold growing in the tank along with bacteria. They generally won’t harm you but can make the water taste or smell bad. This is particularly a problem with municipal water that is stored in open reservoirs. It’s also common to find mold growing in your RV water hose.

To help prevent this, make sure you get a good quality hose that is not transparent to light. I’ve been using this blue hose for the last couple of years, and I really like it. I’ve not had any mold problems in the hose since I started using it. Also, be sure you drain it completely before you put it away. Support my efforts by getting one on Amazon here:

I have many great RV maintenance articles on my site. Check them out here:

Sanitizing an RV fresh water tank is super easy. All it takes is a little bleach and an overnight soak. Be sure and check out my companion video on YouTube

Sanitizing the freshwater tank and water lines

Let’s start by figuring out how much bleach you need to sanitize an RV freshwater tank. The correct formula to achieve the right concentration of bleach in the water is ¼ cup of standard household bleach for every 16 gallons of capacity.


You have a 50-gallon freshwater tank:

Divide the capacity of the tank by 16, so 50/16 = 3.125

Then times that ratio by ¼ (.25 to make the math easy), so 3.125 * .25 = .78 or about ¾ cup of bleach.

So for a 50-gallon freshwater tank, you should add ¾ cup of household chlorine bleach.

NOTE: Do not add extra bleach… Adding extra bleach will not make the tank “extra clean.” It will just make flushing the tank harder and may leave a chlorine taste or smell that is difficult to flush away.

Step-by-step instructions for sanitizing an RV freshwater tank:

  • Download a PDF of the checklist here:
  • If you have a water filter, remove it. It’s best practice to change water filters at least once per year.
  • If you have a water softener, bypass it. It would be best if you did not sanitize your water softener. The chlorine could damage the resin beads and ruin the unit.
  • Bypass the water heater. You do not need to sanitize the water heater. See your owner’s manual for instructions on how to bypass the water heater.
  • If the RV was winterized with antifreeze, flush the water lines with fresh water till they run clean.
  • Fill the freshwater tank at least 1/2 full.
  • Dilute the bleach before adding it to the tank. Put the amount of bleach you determined you needed to sanitize the freshwater tank in a bucket with a couple of gallons of water.
  • Add the bleach and finish filling the tank.
  • If you have a gravity fill tank like most travel trailers, pour the diluted bleach into the tank through the fill port.
  • If you have a pressure tank fill, like on most class A and Class C RV’s, you can use a funnel, drain the water from your hose and pour the DILUTED bleach into the hose. Reconnect the hose to the faucet and finish filling the tank.
  • If you have a winterization kit installed as I do, you can use it and substitute a diluted bleach solution instead of antifreeze.
  • Fill the freshwater tank full.
  • When you have finished filling the tank, turn off the freshwater hose and turn on the water pump.
  • Run chlorinated water through every faucet and fixture in the RV. Don’t forget the bath and shower, external shower, and icemaker if you have one.
  • Turn the freshwater supply back on and top off the tank with water.
  • Turn freshwater off and let the water in the tank sit for at least four to five hours to ensure the tank is sanitized. I like to wait overnight. Note: This is an excellent time to leak check your plumbing. See above for a complete discussion.
  • After you have waited overnight, drain the tank and refill it with fresh water.
  • Turn off the freshwater supply, turn on the pump, and begin flushing the water lines.
  • If the smell of chlorinated water is still present after a few minutes of flushing, drain the tank, refill, and start flushing again.
  • Flush the water heater per the manufacturer’s instructions.
  • Replace the sacrificial anode in the water heater if required.
  • Please turn on the water heater and make sure it is working correctly.
  • Replace the external water filter with a new one.

That’s it. It’s straightforward to sanitize your freshwater tank correctly. If you do, you will have peace of mind that the tank is clean, and you will enjoy clean, fresh-tasting water in your RV. For more great RV How-to information, visit my YouTube page. Happy RVing!

Download a PDF of the checklist here:

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4 thoughts on “How to Sanitize an RV Freshwater Tank”

  1. I have another document that says the ratio is 1/2-cup treats 15 gallons. I am certain yours is closer to what’s actually needed.

    Also in the video you say not to sanitize the ice maker, but item 13 in the downloadable link says to sanitize the ice maker. Just FYI for those who use your suggestions.

    TIP: In our household one of us uses a C-PAP machine and fills the reservoir with distilled water. I take the leftover jugs and use one for the chlorine. One gallon water, 1 cup bleach for sanitization, then rinse with one gallon clean water. I also mark the jug with a Sharpie (Chlorinated Water) and store it for next time.

    1. Thanks, David. I fixed the PDF. No matter how much you proofread things still slip through. The actual amount I used to calculate the concentration of chlorine was 50 ppm. The lowest acceptable amount to sanitize. Others use stronger concentrations that I have found much harder to rinse out. 1/2 cup in 15 gals gives a 100 ppm concentration. Peace

  2. HI TR, Are you concerned about 1 1/2 cups per 100 gallons for everyday use? 2 concerns: one is deteriorating the plastic? and safe to drink?

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