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Old 01-09-2019, 12:52 PM   #1
rhersh
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Shower drain problems

We have a 2016 sprinter 334fwfls.
We have a problem when we use the shower, the water does not drain properly. It will drain slow and eventually the pressure in the tank will build up and blow back through the sink drain, and back up in the shower pan.

I have blown air down through the vent from the roof with no problem, the air came through the drain in the shower, not sure if that is correct or not.
Today took a shower and left the tank drain open just to see if it helped, it did some what but not much.
Any help in this area would be much appreciated. Thanks in advance.
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Old 01-09-2019, 04:12 PM   #2
ctbruce
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Is this just a today thing or has it done this in the past too?
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Old 01-09-2019, 07:39 PM   #3
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No! This has been an ongoing problem since we bought the unit. Tool it back to the dealership twice and they just said they couldn't get it to do it, but every time we use it, it does the same thing.
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Old 01-09-2019, 07:43 PM   #4
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Have you taken the drain out to verify it is functional?
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Old 01-09-2019, 08:30 PM   #5
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Since it's happening with the tank drain open that would eliminate the tank not venting properly. Sounds like there's a restriction in the drain line before it gets to the tank causing a positive pressure to build up enough to blow out your trap in the sink.

Does the shower actually back up and fill with a lot of water or just drain slowly? I wonder if it could have something to do with the slope of the drain lines?
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Old 01-09-2019, 09:32 PM   #6
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Have you taken the drain out to verify it is functional?
Yes I have.
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Old 01-09-2019, 09:33 PM   #7
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Since it's happening with the tank drain open that would eliminate the tank not venting properly. Sounds like there's a restriction in the drain line before it gets to the tank causing a positive pressure to build up enough to blow out your trap in the sink.

Does the shower actually back up and fill with a lot of water or just drain slowly? I wonder if it could have something to do with the slope of the drain lines?
Sorry! I forgot to say with the tank drain open it did not blow back through the sink.
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Old 01-09-2019, 09:41 PM   #8
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Also! It does back up in the shower pan and drains real slow.
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Old 01-10-2019, 05:29 AM   #9
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On most RV's where the bathroom is on a separate gray tank from the galley, the shower AND bathroom sink share a drain to the gray tank. So, first question would be, 'Does the sink drain properly?" If so, then the common drain from below the floor to the tank is OK and the problem is in the branch from the shower drain to where the shower ties into the common drain.

The shower does not have a P trap, but a HEPVO drain trap. That's really a "self closing rubber balloon" inside a plastic tube. One of the most common "failures" for HEPVO valves is installing them upside down. The 5 ridges on the HEPVO must be on the bottom. If they are on the top, the valve will not drain properly.

I'd first check to make sure the sink is draining properly, next I'd check the HEPVO condition and installation. If you've run any chemicals or a snake down the shower drain, you've destroyed the HEPVO and will need to replace it.
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Old 01-10-2019, 06:06 AM   #10
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On most RV's where the bathroom is on a separate gray tank from the galley, the shower AND bathroom sink share a drain to the gray tank. So, first question would be, 'Does the sink drain properly?" If so, then the common drain from below the floor to the tank is OK and the problem is in the branch from the shower drain to where the shower ties into the common drain.

The shower does not have a P trap, but a HEPVO drain trap. That's really a "self closing rubber balloon" inside a plastic tube. One of the most common "failures" for HEPVO valves is installing them upside down. The 5 ridges on the HEPVO must be on the bottom. If they are on the top, the valve will not drain properly.

I'd first check to make sure the sink is draining properly, next I'd check the HEPVO condition and installation. If you've run any chemicals or a snake down the shower drain, you've destroyed the HEPVO and will need to replace it.
Strange that it worked fine for the dealer. Just need to ask, is the 5er level when you have this issue??
Our 2005 Copper Canyon, has a P trap, which got in the way of the basement. So I moved it and in the process improved the slope of the drain line, the shower drains better now, BUT I do notice just a bit of hair, or soap residue will prevent water drain through the small holes of the drain plate. I simply drag my foot across the drain and it drains fine.
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Old 01-10-2019, 06:18 AM   #11
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It was around 2010 or 2011 that most manufacturers switched from P traps to HEPVO valves. I think they did it for two reasons, primarily to eliminate the potential for freeze damage, but also to (as you saw in your trailer) move that "space hog" from the middle of the storage space in most fifth wheel basements. While the HEPVO isn't without problems, it usually is reliable and works well for 4 or 5 years, then, if the "rubber innerds" get stiff or start deteriorating, it's time to replace it. Almost all "new trailer shower drain problems" that I've seen where the HEPVO is involved, it's because the valve was installed upside down.
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Old 01-10-2019, 06:35 AM   #12
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But if it's a problem with the HEPVO drain why would the sink trap be getting blown back up into the sink? To me that points to a problem with the tank venting or the drain downstream being partially plugged.

Have you seen cases where the vent pipe was cut too long and went down into the tank so far that it lost function when a little water got into the tank and covered the opening?

BTW my 2018 Cougar trailer has a regular p trap on the shower drain.
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Old 01-10-2019, 07:18 AM   #13
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Originally Posted by rhersh View Post
We have a 2016 sprinter 334fwfls.
We have a problem when we use the shower, the water does not drain properly. It will drain slow and eventually the pressure in the tank will build up and blow back through the sink drain, and back up in the shower pan.

I have blown air down through the vent from the roof with no problem, the air came through the drain in the shower, not sure if that is correct or not.
Today took a shower and left the tank drain open just to see if it helped, it did some what but not much.
Any help in this area would be much appreciated. Thanks in advance.
Two things stand out to me after reading this again. If you applied air pressure (How much pressure ? ) thru the vent and water & air came out the shower pan (how much water?) then the hepvo valve is not functioning properly.
From the description of the shower and sink "blow back" sounds like the drain line to the tank "burping" to equalize pressure, think pouring a liquid from an upside down bottle. Opening the drain valve didn't help "much" sounds like a venting issue but....
My first step would be a clear connection to the drain line. Fill the tank, then open the drain valve with the clear piece in the hose. The water should drain without hesitation or change in speed or volume. If the water "chugs or gurgles" (like pour from an upside down bottle) then you have a venting issue.
If the water drains from the tank ok, then I'd think you have an issue with common drain line that the shower and sink share. If that is true, then the sink should back up on it's own with use.
I the two questions in the beginning were answered it would help my thinking to confirm or eliminate some things in my way of thinking.
Hope this helps.
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Old 01-10-2019, 08:37 AM   #14
rhersh
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Originally Posted by JRTJH View Post
On most RV's where the bathroom is on a separate gray tank from the galley, the shower AND bathroom sink share a drain to the gray tank. So, first question would be, 'Does the sink drain properly?" If so, then the common drain from below the floor to the tank is OK and the problem is in the branch from the shower drain to where the shower ties into the common drain.

The shower does not have a P trap, but a HEPVO drain trap. That's really a "self closing rubber balloon" inside a plastic tube. One of the most common "failures" for HEPVO valves is installing them upside down. The 5 ridges on the HEPVO must be on the bottom. If they are on the top, the valve will not drain properly.

I'd first check to make sure the sink is draining properly, next I'd check the HEPVO condition and installation. If you've run any chemicals or a snake down the shower drain, you've destroyed the HEPVO and will need to replace it.
The shower has a p trap. The sink drains fine, have never ran chemicals down it.
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Old 01-10-2019, 08:54 AM   #15
rhersh
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Rhagfo
I have double checked level of the 5ver and it is level. I also have run my foot over the drain, some times it helps just a little but not much.
I have resigned myself to probably have to remove the drain pan to get to where the pipes go down to the tank, and redo piping to get it to drain.
The one thing that puzzles me is why does it build pressure in the tank to come back up through the sink.
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Old 01-10-2019, 09:22 AM   #16
rhersh
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Originally Posted by flybouy View Post
Two things stand out to me after reading this again. If you applied air pressure (How much pressure ? ) thru the vent and water & air came out the shower pan (how much water?) then the hepvo valve is not functioning properly.
From the description of the shower and sink "blow back" sounds like the drain line to the tank "burping" to equalize pressure, think pouring a liquid from an upside down bottle. Opening the drain valve didn't help "much" sounds like a venting issue but....
My first step would be a clear connection to the drain line. Fill the tank, then open the drain valve with the clear piece in the hose. The water should drain without hesitation or change in speed or volume. If the water "chugs or gurgles" (like pour from an upside down bottle) then you have a venting issue.
If the water drains from the tank ok, then I'd think you have an issue with common drain line that the shower and sink share. If that is true, then the sink should back up on it's own with use.
I the two questions in the beginning were answered it would help my thinking to confirm or eliminate some things in my way of thinking.
Hope this helps.
1st I only went on the roof and blew down the vent with my mouth, so air came out the shower drain and only spit a little water, none thru the sink. Oh! Shower has a p trap. I have never had the shower drain burp back while using it or while using the sink. I can fill the sink several time and drain it with no problem at all. When I drain this tank I have a clear plastic on it and the water drains without gurgling or burping and never changes speed.
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Old 01-10-2019, 09:37 AM   #17
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My vote is for some kind of restriction in the drain line before it goes into the tank. I would find an accessible location if possible and cut the drain line so I could check it clear in both directions. Pretty easy and quick. Then you can splice in a new piece of pipe or just use a flexible coupling to put it back together. And check out the routing of the drain to make sure they're not trying to make water run uphill! [emoji16]
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Old 01-10-2019, 09:47 AM   #18
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I have to agree with you on this, I was just hoping that there might be a simpler answer to the problem since I have to pull the shower pan to do it. I'm getting a little lazy in my old age.🤣🤣
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Old 01-10-2019, 10:54 AM   #19
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Steveo57
I have to agree with you on this, I was just hoping that there might be a simpler answer to the problem since I have to pull the shower pan to do it. I'm getting a little lazy in my old age.🤣🤣
You know now that I think about it I have a similar issue with my shower if the drain cover gets a little hair and scum on it. It will drain slowly and back up into the shower pan. Works fine if I keep the drain cover clean. That doesn't explain the sink trap burping though.

I'd look at pulling the traps and carefully snaking the lines out before I'd pull the shower pan. Your right that would be a LOT of work! You could also look into a little inspection camera to shove down the lines and see what's going on. They're pretty cheap nowadays.

You could also cut an access in the wall on the other side of the plumbing if possible to get better access. I did that on mine to get to the back of the water heater and power panel. Then you put a nice access cover over it and you'll always be able to get in there to fix stuff or check for leaks etc.
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Old 01-10-2019, 11:22 AM   #20
rhersh
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You know now that I think about it I have a similar issue with my shower if the drain cover gets a little hair and scum on it. It will drain slowly and back up into the shower pan. Works fine if I keep the drain cover clean. That doesn't explain the sink trap burping though.

I'd look at pulling the traps and carefully snaking the lines out before I'd pull the shower pan. Your right that would be a LOT of work! You could also look into a little inspection camera to shove down the lines and see what's going on. They're pretty cheap nowadays.

You could also cut an access in the wall on the other side of the plumbing if possible to get better access. I did that on mine to get to the back of the water heater and power panel. Then you put a nice access cover over it and you'll always be able to get in there to fix stuff or check for leaks etc.
I was thinking about running a snake down it, but the pressure build up always stumped me. I will run a snake through it and go from there.
Never thought about opening up plumbing from back side, thanks for bringing it up. By the way where did you get the access cover at? And thanks for your help and ideas.
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