Black Holding Tank slow to drain...

[mgirardo]

Our Black Holding Tank is slow to drain. Can this be caused by a bad Air Admittance Valve or a clogged vent cap or both? The tank dumps fine at first, but it eventually backs up and then very slowly drains. The grey tank does not do this. It flows just fine.

Thanks in advanced,

-Michael

[schlep1967]

Sounds to me like you may have the disk they cut out to install the drain line still in the tank. As everything moves towards the drain it brings the disk with it until it gets to the tight spot then it jams up.

[K_Charles]

2oldman wrote:
You can verify if it's air intake by holding open the toilet.

This X 3

[MarkTwain]

1. put a water hose in the toilet and fill black tank about 3/4 full then open black tank valve, leaving the water hose running. Repeat process 2 or 3 times. If this does not resolve the issue call the local septic tank removal business and have your tank emptied.

[Sam_Spade]

kgie1217 wrote:
Sounds like you have a build up of waste (ie, toilet paper, feces). Have you done a flush yet?

This.

2oldman wrote:
You can verify if it's air intake by holding open the toilet.

And this.

[korbe]

mgirardo wrote:
but it eventually backs up and then very slowly drains.

Backs up?

[2oldman]

You can verify if it's air intake by holding open the toilet.

[kgie1217]

Sounds like you have a build up of waste (ie, toilet paper, feces). Have you done a flush yet?