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.

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

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.

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.

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.

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.

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

39 Replies

univmd
Explorer
Jan 22, 2020
We don’t pre-add water. We go to the bathroom a lot though so it never really dries out.
jdc1
Explorer II
Jan 17, 2020
bikendan wrote:
3-5 gallons.

Correct answer (and a couple others). Use granular laundry soap once in while too, before traveling (said prior). That stuuf they sell to breakdown solid waste is useless....It's just deoderizer.
OleManOleCan
Explorer
Jan 17, 2020
Second Chance wrote:
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

I adopted the Geo Method a number of years ago. After I dump the Black tank, I like to put in a 1/2 bottle of Calgon and a good bit of dish soap. I top it off with 3-4 gallons of water. The ride to my home cleanses the tank. I do he same with my Grey Tank. BTW: It never hurts to put some in your sink traps. No odors...
ppine
Explorer II
Dec 19, 2019
Nada.
rvshrinker
Explorer III
Dec 19, 2019
I just hold the toilet plunge open for a minute or so. No problems.
Edd505
Explorer
Dec 18, 2019
black tank flush after dumping & closing the black valve 3-4 minutes, yes minutes. I drive to the next RV Park and dump as needed. When leaving, dump flush and add as stated. Repeat, not a chance it will clog and the clean water driving helps breakup & clean for the next stop. I have a 57 gallon black and it takes weeks to fill with the added water.

(1 minute = 3-5 gallons depending on flow rate)
doxiemom11
Explorer II
Dec 17, 2019
Couple of full bowls, and generous water when flushing, never any additives. We are full-time though, so it is always being used.
ReneeG
Explorer
Dec 17, 2019
NRALIFR wrote:

You might also check to make sure she isn’t leaving the black tank valve open all the time. That will cause problems for sure.

:):)

Bingo! When hooked up at a park, leave your tank valve closed and don't open it till you dump it prior to leaving. Leaving the valve open allows liquids to flow through and the solids to sit. You need all the liquids in it to move the solids.
bigred1cav
Explorer
Dec 17, 2019
5 gallon and a 10 pound bag of ice
edatlanta
Explorer
Dec 17, 2019
Oasisbob wrote:
In my 17 years with this trailer I have never even considered adding water. My bathroom sink does empty into black however. I do use an internal on board sprinkler type sprayer when I dump where available. Maybe that helps?

I am now 9 years+ full time and I NEVER add water after a dump. I do boondock a couple of weeks a year and really want full black tank capacity when I start. If you are going to be using it why start out with extra water in the tank?