Saturday, May 28, 2022


Spring cleaning time for fresh water tanks

Here are sure signs you need to disinfect your RV fresh water system:

  • Your significant other takes a drink of water and their face wrinkles up like a raisin.
  • You take a shower and come out covered with algae.
  • You fill up your fresh water tank—and then notice a sign warning a “boil water advisory is in effect.”

Really, if your rig has been snoozing all winter and you remember that you forgot to drain the system down, aside from fixing broken pipes, it’s not a bad idea to do a disinfect. It only takes about one mouthful of “yecchh!” water to convince you that water can go stale. What to do? Well, this is the same trick we recommend before you use the water system on any “new to you” RV.

Step by step

1. Completely drain the fresh water holding tank. Fire up the water pump and open taps until all water is out of the system. If your water heater is “in the circuit” (meaning not winterized, but holding water), drain it too, using the drain cock on the heater. Big fat caution: Make sure the water is COLD before draining it.

2. Determine the fresh water tank capacity. Easy enough if you have an owner manual. If not, measure the fresh water tank. Break down the feet and inches to decimals, e.g., a 4’6″ run is 4.5′. Multiply the height, width, and depth figures and you’ll have the tank’s capacity in cubic feet. Now multiply the cubic feet by 7.48051945 and voila! You now know the capacity in gallons.

3. Using unscented household bleach (8.25% of sodium hypochlorite) and a clean container (a cleaned up juice jug or empty gallon drinking water jug is ideal), mix up a solution in this way: For each 15 gallons of tank capacity, pour in 1/4 cup of bleach, then top off the jug with fresh water.

4. Make sure your fresh water drain valve is closed (and the water heater, if applicable), and pour this bleach solution into the holding tank. Now completely fill the fresh water holding tank with clean, fresh water. At this point, if you can, move your RV around the block to thoroughly swish and mix the solution in the tank.

5. Turn on the water pump and pump the bleach solution through all the plumbing. You’ll know when you’ve pumped enough as you should smell the bleach solution at the fixture. Let solution stand in the plumbing and fresh water tank overnight. Next day, drain the fresh water tank (and again, the water heater, if applicable), and refill the fresh tank with clean, fresh water.

Get rid of that yucky chlorine taste

If you’re concerned about the remaining chlorine taste or odor, mix up a solution of 1 quart of cider vinegar for every five gallons of tank capacity and dump it in the fresh tank, repeating the same process you did for the bleach job.

Ever get caught somewhere with a dry tank and need to use surface water in an emergency? Here’s how you can safely do it



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19 days ago

Step 4 says fill the fresh water tank. Depends on your RV. Many, especially upscale Class A Motorhomes, do not have a fill port and can only be filled with a hose which requires a pressurized source. I use a small tank gizmo with hose threads on both ends (and a fill plug of course), previously recommended in RVTravelForum, that I can fill with bleach then insert the gizmo in the water line that then uses shore water pressure to load my tank with the bleach/water mix.

21 days ago

Says to drain the freshwater tank and then turn the pump on. There will be nothing to pump and may damage the diaphragm in the pump. Drain tank and then fill it with the bleach solution then turn on the pump to fill all the lines. Fill the tank again and allow it to sit over night.
I then drain the tank using the tank drain and fill it with fresh water and flush the system.

21 days ago
Reply to  Bob

PS: I also open the low point drains when draining the tank

Kimberly G.
21 days ago

I use the same process using 1:1 water to white vinegar mix. Vinegar helps dissolve hard water scale and is more environmentally friendly than bleach. Great article!

21 days ago
Reply to  Kimberly G.

Vinegar will not kill organisms, you need an oxidizer like bleach for that. After bleach reacts with something you are left with sodium chloride, table salt. An alternative to vinegar for descaling is citric acid, having no odor.

21 days ago
Reply to  Kimberly G.

More environmentally safe, but doesn’t disinfect at all, which bleach does.

21 days ago

I think you should blow out the water in lines (if any), before turning on pump. Best to do this first thing bring out of storage, all water is out just blow out the antifreeze first and do cleaning.