I have an interesting problem that I have never seen before. During our last outing, I noticed there was standing water in the shower drain after the first shower was taken in the rig. I found it hard to believe that the grey water tank needed dumping already. So I opened all the valves to the tanks to drain all the water/wastewater. Still had standing water in the drain. I poured a bucket of hot water down, thinking maybe there was a clog and it would rinse it out. Interestingly enough, the water drained fast, but yet there was still standing water in the drain. We took another shower, and there was never any problem with a slow drain (the water drained fine and never backed up), but always standing water inside the drain.Brought the rig home and drained out everything - grey, black, fresh, low-point drains, etc. Still standing water in drain. Used the vinegar & baking soda solution but it didn't help. Tried flushing it with the garden hose - nothing. Tried using that plastic hair drain tool - nothing. I am stumped as to why I can get all the water flushed out of the shower pipes.After looking at the piping, it looks like there is no p-trap for the shower drain. Anyone have any suggestions as to what my problem is and how I can fix it?

Some RV's use a "Hepvo" or similar inline seal instead a traditional 'P' trap. The rubber "flutter valve" seal opens when there's sufficient flow through it, and it's normal to see some retained water in the drain. As the valve ages, it can get stiffer and retain more water than when new.Hepvo Waterless Valve

Dutch_12078 wrote:Some RV's use a "Hepvo" or similar inline seal instead a traditional 'P' trap. The rubber "flutter valve" seal opens when there's sufficient flow through it, and it's normal to see some retained water in the drain. As the valve ages, it can get stiffer and retain more water than when new.Hepvo Waterless ValveLikely the problem. If you have room to replace it with a P trap, that would be good.

So is the water standing in the shower pan or only down in the drain. There is supposed to be some water in the drain. The water is what keeps the tank smell from coming into the trailer.

Use a toilet plunger and blast it out.

Shower clog or something else? | Good Sam Community

Dutch_12078
Explorer II
Jul 14, 2020
Some RV's use a "Hepvo" or similar inline seal instead a traditional 'P' trap. The rubber "flutter valve" seal opens when there's sufficient flow through it, and it's normal to see some retained water in the drain. As the valve ages, it can get stiffer and retain more water than when new.

Hepvo Waterless Valve
larry_cad
Explorer II
Jul 14, 2020
Hair buildup in the drain.
Lynnmor
Explorer
Jul 14, 2020
Dutch_12078 wrote:
Some RV's use a "Hepvo" or similar inline seal instead a traditional 'P' trap. The rubber "flutter valve" seal opens when there's sufficient flow through it, and it's normal to see some retained water in the drain. As the valve ages, it can get stiffer and retain more water than when new.

Hepvo Waterless Valve

Likely the problem. If you have room to replace it with a P trap, that would be good.
Roger10378
Explorer II
Jul 14, 2020
So is the water standing in the shower pan or only down in the drain. There is supposed to be some water in the drain. The water is what keeps the tank smell from coming into the trailer.
Fisherman
Explorer
Jul 14, 2020
Use a toilet plunger and blast it out.
pigman1
Explorer
Jul 14, 2020
Fisherman wrote:
Use a toilet plunger and blast it out.
That'll work, but go easy at first. I usually have the problem on the first shower after a long dry spell. When still in the shower I stomp hard on the drain a few times with the ball of my foot. Works every time for us. After the first time it usually works fine for the rest of the trip.
dougrainer
Nomad
Jul 15, 2020
Fisherman wrote:
Use a toilet plunger and blast it out.

NEVER DO THIS WITH A HEPVO VALVE!!!!!!!!!!!!!!!!!!!!!!! THE PLUNGER SUCTION ACTION WILL PULL THE HEPVO VALVE "DUCK" LIPS BACKWARD TOWARDS THE DRAIN, RENDERING IT ALMOST USELESS. HOW DO I KNOW THIS??????? I DID THIS A FEW YEARS AGO AND MADE THE PROBLEM WORSE. I THEN PULLED THE HEPVO VALVE AND FOUND THE LIPS PULLED BACKWARD. LUCKILY YOU CAN JUST PUSH THEM THE OTHER WAY ONCE IT IS PULLED. Doug
remdog_1
Explorer
Jul 15, 2020
Check the grey tank vent for blockage. If vent clogged it won't drain
dougrainer
Nomad
Jul 15, 2020
If the water is NOT in the shower pan but you can see it below the round strainer, that is NORMAL. For either a Hepvo or P trap system. That is your Water barrier to keep gas/odors from coming back up. Doug
BeeDub
Explorer
Jul 15, 2020
dougrainer wrote:
If the water is NOT in the shower pan but you can see it below the round strainer, that is NORMAL. For either a Hepvo or P trap system. That is your Water barrier to keep gas/odors from coming back up. Doug

So that is exactly the situation I have. But I guess my concern is that normally when I open all the valves to drain all the tanks, especially in fall when I winterize, I don't ever recall seeing this water down in the drain. Everything is functioning properly the way it should, so for now I won't worry about it.