water backing up into shower pan????

[kewpie]

Hello,

Can anyone help me with the problem I am having with waste water from my sink backing up into my shower pan.? If I wash a load of dishes and then let the sink stopper go, the water backs into my shower pan.

I do have the sink and shower plumbed so that I can either dump into the black tank, or by-pass into a hose that eliminates grey water.

Help, this is really not an ideal situation.
Thanks Kewpie

[HowieE]

Assuming the tank is not full and this only happens during the sink draining and then drains down in the shower the flow rate is too high for the hose you are using.

I would try and make a stopper for the sink that slows the drainage rate. The shower is the lowest point and will show any backup first.

[pmclemore]

I'd suspect that something is wrong with how the plumbing was changed from the "standard" of sink-goes-to-gray-water. Has it worked in the past?

Pat