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Spade_Cooley's avatar
Spade_Cooley
Explorer
Dec 13, 2019

How much water to ad to black tank when starting out.?

I'm not a beginner and have never had trouble with blockage but know a number of people who have, My neighbor in this RV park is currently stopped up and had to buy a solution to dump into her tank to free it. I normally ad between 3 and 4 gallons of water and two containers of treatment to start out and have never had a problem. What is the minimum you should start out with in the black tank. Is it different while driving on a trip than when you are stationary in a park? Opinions will be respected.

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  • Ed_Gee's avatar
    Ed_Gee
    Explorer II
    Dec 13, 2019
    I usually use the tank sprayer after dumping so after a few minutes of rinsing, I close the black tank valve but leave the sprayer going long enough add at least a gallon or two.
  • cavie's avatar
    cavie
    Explorer
    Dec 13, 2019
    two full bowls of water should do the trick. Never leave it dry.
  • Lynnmor's avatar
    Lynnmor
    Explorer II
    Dec 13, 2019
    The pipe from the tank to the dump valve needs to be filled plus a few gallons more. Some dump valves are right on the tank and some are quite distant, so the answer will not be a certain number of gallons. If you can see the tank bottom, measure the number of gallons or bowl fulls it takes to cover the bottom of a completely empty tank. When using an additive to control the odor, don't add it till the water fills the aforementioned piping so it is in the tank.
  • wildtoad's avatar
    wildtoad
    Explorer II
    Dec 13, 2019
    I never add water to the black tank when starting a trip cause I always keep some water in it which I think is the best thing to do to prevent “stuff” from sticking to the bottom, sides, valves. After I dump and flush, I simply put one or two toilet bowls worth of water in the tank.
  • shum02's avatar
    shum02
    Explorer
    Dec 13, 2019
    I usually say about 10% of the capacity of the tank. Has worked great for me, never had a problem. Dish or laundry detergent are the only two chem's that I add to my tanks, again, not a problem.
  • schlep1967's avatar
    schlep1967
    Nomad
    Dec 13, 2019
    My opinion. It really depends on your black tank. You need enough water in it that solid waste can be mostly or completely submerged so it can soften up and or break down.
    And yes it is different if you are sitting in a park vs moving around "stirring" the contents of the tank. The treatment chemicals are more important when sitting still.
  • midnightsadie's avatar
    midnightsadie
    Explorer II
    Dec 13, 2019
    I have a smaller rv only 24ft I put about a gal of water in the tank ,just its not sitting dry no chemicals. we empty the tank after each trip and hose out . I think thats the answer to not having a clogged tank.
  • Second_Chance's avatar
    Second_Chance
    Explorer II
    Dec 13, 2019
    Like you, I put about 4 gallons of fresh water in the black tank after emptying - but I've never used any additives. I've also not had any issues in over four years of full-timing. Several times a year I will use the "Geo method" to clean the tanks: about 1/3 tank of clean water with some dish detergent and borax crystals before hitting the road. The agitation and solution help clean off the level sensors and get residual "stuff" off the sides of the tank(s).

    Rob

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