Shower not draining - help!

[Rene T]

Rene, you were correct in your original answer; there is a fourth gate! The fine folks who winterized my Trailer must?ve closed it.  The 3 visible gates are Grey, Black, and dual drain.  Way far back is another grey that was the culprit...

Whew!! Thanks for getting back to us.

What do you mean by dual drain?

 

[Popquizz]

3 visible gates are Grey, Black, and 3rd releases both liquids to sewer line. The 4th is about 3 ft under trailer for grey water coming from rear of trailer. It looks like it was added post production. The previous owner was a fix-it guy. Lol

 

[Rene T]

3 visible gates are Grey, Black, and 3rd releases both liquids to sewer line. The 4th is about 3 ft under trailer for grey water coming from rear of trailer. It looks like it was added post production. The previous owner was a fix-it guy. Lol

Is the valve #3 located on the end of the sewer pipe? Some people install what's called a spin on valve on the end of the sewer pipe to be used as a backup valve in case one of the tank drain vales is leaking a little.
When dumping valve #3 should be left open. Then dump your black tank first then dump your gray tank to flush out the sewer hose.

 

[lynnmor]

They probably added that 4th valve so that both tanks could take on water, then the valve would be closed while traveling so that one would not be overfilled causing a flood.

 

[Popquizz]

I am unaware of rhyme or reason for the fourth, but it is set back far enough that it is not reachable on blended knee. I needed to shimmy under the trailer a little to grab it.

 

[kdbgoat]

The one gray tank valve that I posted about earlier was the same way. The handle was mounted with a bulkhead fitting to the frame. Yes, it was factory.