Bathroom sink back-up

[capswin]

2021 Grey Wolf 23MK
Bathroom sink backs up when gray water reads 2/3 full. I was at full hookup so I pulled the gray water valve and it drained. Since this drain is higher than the shower, I would think that the shower would back up first. Do I have some type of vent problem maybe?

[fonzie]

Some trailers have the shower drain into the black tank.

https://www.google.com/search?q=show...iverforums.com

[bikendan]

Originally Posted by fonzie

Some trailers have the shower drain into the black tank.

https://www.google.com/search?q=show...iverforums.com

and some have the bathroom sink drain into the black tank, instead of the gray tank.

[nomad297]

You do have a venting problem.

The reason this is happening is because the vent for the tank is protruding into the top of the tank farther than it should be. Once the level of the water in the tank reaches the bottom of the vent stack inside of the tank, the sink you are having problems with and any other fixtures connected to the gray tank will not drain properly, if at all, because the tank is no longer vented, so there is no vent to atmosphere to allow for the displacement of the water entering the tank. Your shower isn’t backing up because your tank isn’t full. It may be draining, but probably not as well as it should be.

The only solution is to have the vent pulled out of the tank to the correct penetration length, which should be minimal to maximize the amount of water that will flow freely into the gray tank.

Bruce

[capswin]

Originally Posted by nomad297

You do have a venting problem.

The reason this is happening is because the vent for the tank is protruding into the top of the tank farther than it should be. Once the level of the water in the tank reaches the bottom of the vent stack inside of the tank, the sink you are having problems with and any other fixtures connected to the gray tank will not drain properly, if at all, because the tank is no longer vented, so there is no vent to atmosphere to allow for the displacement of the water entering the tank. Your shower isn’t backing up because your tank isn’t full. It may be draining, but probably not as well as it should be.

The only solution is to have the vent pulled out of the tank to the correct penetration length, which should be minimal to maximize the amount of water that will flow freely into the gray tank.

Bruce

Thanks for the input. Doesn’t sound like an easy fix.

[Reverse_snowbird]

First check to see if that sink drains into the black water tank. We accidentally left a small stream of water running into the bathroom sink and it eventually filled the black water tank. When that happened, the water (fresh, thank heavens) started to overflow. Turned off the water, dumped the black water tank and problem solved...... Well, except for the fact we have to watch how much water we use in the bathroom sink.

[msdenice]

Originally Posted by capswin

2021 Grey Wolf 23MK
Bathroom sink backs up when gray water reads 2/3 full. I was at full hookup so I pulled the gray water valve and it drained. Since this drain is higher than the shower, I would think that the shower would back up first. Do I have some type of vent problem maybe?

Was just wanting to know if you got yours fixed, and if so what did you have to do to fix it. Appreciate any info you have.

[capswin]

Originally Posted by msdenice

Was just wanting to know if you got yours fixed, and if so what did you have to do to fix it. Appreciate any info you have.

Haven't figured out anything yet. My next move is to put 5 gallons of water down the drain at a time to try to figure out how much the tank needs to have in it to start to back up.