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Installing black water tank

Our_rolling_oas
Explorer
Explorer
We are installing a black tank with a shallow end and a deep end on the tank. It slopes from shallow to deep. Does the hole for toilet waste go over the shallow or deep end?
20 REPLIES 20

JRscooby
Explorer II
Explorer II
Everything is a compromise. I think best would be toilet over deep end, just so less water is needed to keep things wet. And best for draining tank would be have the hole in bottom instead of side. That way as the level drops, the pipe would stay full longer.

oldave
Explorer
Explorer
Realistically, I don't think it matters very much where you place the toilet as long as the hole and the toilet line up. You are converting a bus, so that alone implies that you understand things. In this case, water is your friend. After dumping I add approx 5 gal of water, this will eliminate virtually all black tank problems. I try to let the black tank get nearly full and then dump, this gives a powerful flow that evacuates practically everything.
I usually dump just a little grey water first, so that I can see if I have a leak or any other problem. If all seems ok, I let the black water flow, followed by a tank full of grey water to wash out the 3" sewer hose.

Our_rolling_oas
Explorer
Explorer
Class A Customs 40 Gallon RV Waste Black Water Holding Tank WT-4000 https://a.co/d/bbs0yyL

Above is the link for the black tank we purchased.

Our_rolling_oas
Explorer
Explorer
Thank you. Yes,we are converting a bus to an RV so this is a new install. Thank you for all the input. Much appreciated.

oldave
Explorer
Explorer
I haven't re-hydrated any but others that have dealt with the problem didn't seem to think it re-hydrated that easily. At any rate, keeping it wet resolves the problem and has kept me from having to find out the hard way.

opnspaces
Navigator
Navigator
Dried poop is only like concrete when it is dry. If you put it in water it will re-hydrate. The issue is when people try to conserve water by using only a tiny amount of water to flush. Or they leave the black drain valve open and try to use like a residential toilet.

Short answer, don't do the two things above and you will be fine no matter where you put the hole in the tank.
.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup

oldave
Explorer
Explorer
Usually, we would cut the hole to line up where the toilet is, but you don't seem to be concerned about that so you must be remodeling.
I would place the toilet over the deep end, because of the chance of water not covering the shallow end at some point. The deep end is where water is most likely to be. Dry poop will turn to concrete and you don't want that.

JRscooby
Explorer II
Explorer II
johnhicks wrote:
Isn't it going to be dictated by where the toilet is?


Or the placement of toilet dictated by shape/placement of tank?

ArchHoagland
Explorer
Explorer
Our rolling oasis...What is the year, make and model of your RV?
2004 Monaco La Palma 36DBD
Workhorse W22 8.1 Gas Allison 1000, 7.1 mpg

2000 LEXUS RX300 FWD 22MPG 4020 LBS
US Gear Brakes

opnspaces
Navigator
Navigator
On my trailer the the tank slopes from shallow on the ends to deep in the middle. Hence the toilet sits over the shallow end. I doubt it really matter which end yours is over. Use water for the flush and don't dive it a second thought.
.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup

RLS7201
Explorer
Explorer
It is common practice to put some water back in the black tank after dumping, to stop the pyramid of poop. That water will be in the deep end, so I suggest the toilet goes over the deep end. That's the way is was done on my MH.

Richard
95 Bounder 32H F53 460
2013 CRV Toad
2 Segways in Toad
First brake job
1941 Hudson

johnhicks
Explorer
Explorer
Isn't it going to be dictated by where the toilet is?
-jbh-

JRscooby
Explorer II
Explorer II
Don't know much about the tank, but I do know you don't want sewer lines sloped very steep or water will run off and leave the solids. If need to go down much grade you step the line so slow flow, drop, slow flow.
Why would you force solids to travel any farther than needed in tank? Drop them in as close to where you expect them to go out as you can.

way2roll
Navigator
Navigator
How shallow vs deep are we talking? I don't think pre constructed black tanks have that much of a slope. For physics sake you want some but nothing dramatic as it will decrease capacity. I doubt RV manufacturers put much thought into where the hole will go other than how does the tank fit in the chassis and where the toilet is on the floorplan.

Jeff - 2023 FR Sunseeker 2400B MBS