Forward black tank not draining

[Balvind]

I bought a 2016 Jayco pinnacle from a private party. The forward half bath toilet tank does not drain all the way. You can drain it with the black tank lever and then look down the toilet and still see liquid. Why does it not drain all the way. What can I do to fix this. All help is appreciated. The rear toilet and tank works fine.

[JFlightRisk]

Welcome to the Forum from Western New York State!

Some of the black tanks are shallow enough, so it looks like there's a lot of liquid when it's really empty. The depth is around 7 or 8 inches. The sensors are inherently inaccurate, so you may not be able to go by them.

[Balvind]

No. There is water in it. I can see several inches in the tank. It is a straight down hole.

[TWP723]

Valve not opening all the way maybe?

[Grumpy]

Originally Posted by Balvind

No. There is water in it. I can see several inches in the tank. It is a straight down hole.

If the tank has a slight belly it will also look worse than it is.

[Scottenj]

Originally Posted by Balvind

I bought a 2016 Jayco pinnacle from a private party. The forward half bath toilet tank does not drain all the way. You can drain it with the black tank lever and then look down the toilet and still see liquid. Why does it not drain all the way. What can I do to fix this. All help is appreciated. The rear toilet and tank works fine.

My black tank never drained all the way and was always over half full!

There were two problems:

The first issue was the outlet pipe was installed incorrectly and went “up hill” about 4”, since the tank is only around 7” deep, that held in over half the effluent.

The second issue was the tank was sagging in between the supports and didn’t have a consistent downward pitch.

I would suggest opening up the Coroplast and looking to see what is going on. Depending on where you tank is you may be able to open the back wall of the basement and see the outlet pipe but to really check it you will need to drop the Coroplast.

[norty1]

If it's water, I would not be to concerned. I usually add 3-4 galloons to my black tank after emptying anyhow. I would remove part of the belly and look at the pipe routing.