Can Waterless Waste Trap Cause Shower Drain To Back Up

[Camarillodoug]

The shower drain in our 2014 Winnebago Sightseer 30A drains very slowly and water stays in the drain.  We purchased our 2014 Sightseer used in December 2016 and the drain has always been slow but it seemed to be getting worse.  I assumed that the drain was likely clogged with hair.  So I used a coat hanger with a hook on the end to try to unclog the drain and to pull out hair.  This did not improve the drain, and when I removed the coat hanger after numerous uses no hair or other stuff was caught in the coat hanger hook.  I also tried using long tweezers to reach into the drain to remove any material clogging the opening but got nothing with the tweezers.  So I used a water heater flush wand hooked to the water hose which I put into the drain about five inches. When I turn on the wands valve, the water runs freely down the drain and does not back up.  Once I turn the water heater wand valve off , the water comes back up to the top of the drain.

From the Winnebago schematics for the Sightseer, the shower drain runs (about 27 inches) under the length of the shower pan to the sidewall and makes a 90 degree turn and then runs about two and a half to three feet where the drain from the bathroom sink connects to the drain.  About four inches past this connection with the bathroom sink drain there is a waterless waste trap.  Approximately nine inches past the trap the drain makes a 90 degree turn and a foot or so later it drops into the grey waste tank.

The bathroom sink drain does not back up into the sink when I leave the sink faucet on.  I'm beginning to think that somehow the waterless waste trap is preventing the shower drain from draining.  Unfortunately, to service the waterless waste trap, it appears I would need to remove the water heater as the trap runs along the side wall directly under the water heater which is located under the bathroom sink.

Here is the link to the Sightseer's Plumbing Diagram http://www.winnebagoind.com/diagram/2014/14_d30a_plumb.pdf

Any thoughts you have would be appreciated.

 

[Henry J Fate]

The waterless trap could be the cause. I do not have first hand knowledge of one of those failing but based on the design, a bad diaphragm could cause the problem.

The sink drain will place more pressure in the plumbing than the shower drain and could be the reason why the sink drain appears to overcome the restriction in the waterless trap.

Also...The shower drain is much more sensitive to levelling. Make sure that the current level of the MH is not contributing or causing the problem.

According to your bathroom layout, it looks like the waterless trap is under the base of the bath vanity. Hopefully it will be easier to get at without removing the water heater.

 

[Camarillodoug]

Thanks Henry for your comments.  I'm thinking the same, i.e. that the sink drain puts more pressure on the bladder in the waterless waste trap.  After I made the post, I realized I should have ran the bath faucet and the shower at the same time to see if the shower will drain properly given that the bathroom faucet running apparently fully opens the bladder in the waterless waste trap.

 

[ChasA]

You should never stick anything in one of those traps. We have one under the shower in our coach. When it gets slow, we pour and entire small bottle of drain cleaner in it. It works fine and will not harm your plumbing.

 

[SpencerPJ]

You should never stick anything in one of those traps.

X2  especially a coat hanger.   
That would be a costly repair


Possibly disassemble your shower hose, (be careful not to lose and rubber washers) and stick it down the hole, place hand or rag around hose and seal as best you can, them run hot water at moderate pressure to flush any potential debris through the system.

 

[Henry J Fate]

It sounds like a hose was placed in the drain with the water heater flush attachment and it took everything he gave it without backing up but as soon as he stopped, the water level came back up.

One test that might be helpful would be to fill the vanity sink to the max with water then open the stopper. See if any water backs up into the shower.

My 2001 winnebago brave had a similar problem with the tub. It wasn't a blocked line. It was a bad service line that had lost its pitch over time. I determined that the design was also in question so I revised the piping and have had no problems since.

If you have concluded that the piping is clear it will probably be either a pitch problem or the waterless trap.

If the shower took a really good pounding of pressure and water with the water heater flush and did not back up, it is safe to say that you don't have a clog.

It seems more likely to be a pitch issue if the water is staying at the same level. Either a piping problem or the MH leveling or a combination of both.

The key is if the level always stays constant. For example if you look at the level and it's right up to the tub line, look at it an hour later to see if it changes. If it stays the same, pitch and level seem to be more likely. If it falls below the starting level, probably that waterless trap.

 

[Gary RV_Wizard]

Since both the bath sink and the shower drain through the same waterless trap, a problem in the trap should effect both. The possible difference is the water volume - showers run a greater volume for a longer time. A slow running trap might cause the shower to back up whereas the the sink squeaks by.  Henery gave solid advice on that possibility, but I would try the drain opener option first (ChasA suggestion).

 

[John Canfield]

Welcome to the forum.  )

 

[Camarillodoug]

Thanks for all your thoughts and suggestions.  I raised the height of the passenger side of the Sightseer to +.7 of a degree using the jacks and thereby increased the incline of the shower drain pipe.  I then ran the shower and the water seemed to drain properly although there was still water in the drain but below the top of the drain.  Apparently the effectiveness of the drain is very susceptible to the pitch of the motorhome.

As Henry Fate suggested, I also filled up the sink with water and opened the stopper.  Water in the shower drain did back up slightly into the shower pan but went back down shortly after the sink was empty of water.  The waterless waste trap may also be contributing to the drainage problem when water pressure in the drain is low.  Because as I stated in my original post, when I put the small hose (the water heater flush wand) into the shower drain and opened the hose's valve no water backed up into the shower. 

 

[Henry J Fate]

It seems something has changed if you were not experiencing this problem previously. Like Gary mentioned, I would clean the line from the shower pan to the waterless trap to be sure things have not been building up in there. That section of line is at a greater risk of blockages from the sitting water and the slow drainage. 

Putting chemicals in the drain may not be friendly to the bladder of the trap and it should be researched before doing so.  Snaking the line  would put the bladder at risk. The bladder is responsible for stopping gray tank odors from coming up through the vanity sink drain and the shower drain and into the cabin. Those odors can be quite fowl at times and even worse than the black water odors.

A good way would be to waterjet the line. It would probably be a good idea to see what is available for water jetting. Your idea of using the tank flush was a good one. If you could extend something like that through the drain line and up to the trap, you would probably clear out anything that has accumulated in there.

Also.... It might be a good time to figure out how to access the trap. It looks like it could be located in the bath vanity under the sink or possibly under the floor of the vanity. It may also be a good time to figure out if there is any way to get a look at the plumbing from the shower pan to the trap. you may find that something has changed in that section of pipe. It could be as simple as the pan flexing closer to the floor and reducing the pitch to the trap.

Hope it all works out and good luck