Gray Tank Problem

padamas · 01-23-2018, 11:36 AM

Our gray tank drains slowly and bubbles (bloop...bloop) like an inverted pop bottle as air trades places with liquid. Has anyone else had this problem, or is it something we must accept as normal ?

Our only other trailer experience was with our Bigfoot, and it's gray drained 'whoosh' like the black tank.
Any ideas or suggestions out there?

Thanks,
Patrick

**Donna D.** · 01-23-2018, 11:48 AM

Yeah, welcome to the slow gray draining crowd. It helps to make certain all the drains inside the trailer are open... kitchen, bathroom sink and shower.

Ron in BC · 01-23-2018, 12:04 PM

On the 19 there is a roof mounted vent that allows for air to replace draining liquid. It sounds like you have a vent issue.

While the sink drain etc. do connect to the grey tank they have a water filled trap which reduces their effectiveness as vents. It's the roof vent that does the most venting.

On the 19 the grey tank is flat and the drain is on the side which means that it's usual for the last of the liquid to take longer because of the reduced cross-sectional area of the pipe. But gloop-gloop isn't normal.

Ron

SFDavis50 · 01-23-2018, 02:45 PM

I have a 2017 5.0TA and the grey tank drains OK.

I don't have the bathroom sink so I also think there isn't a "cheater" vent in the wall behind the shower; just the shower drain and the sink drain. Also, my stove and sink are swapped so there is a much longer 2" drain pipe running from the sink along the bottom of the cabinet to where it drops thru the floor into the grey tank. I believe that pipe allows a greater volume of air to exchange as the grey tank drains. I always run water into the two drains after emptying the grey tank to refill the traps just in case they are empty.

rubicon327 · 01-23-2018, 03:15 PM

Quote:

Originally Posted by Ron in BC

On the 19 there is a roof mounted vent that allows for air to replace draining liquid. It sounds like you have a vent issue.

While the sink drain etc. do connect to the grey tank they have a water filled trap which reduces their effectiveness as vents. It's the roof vent that does the most venting.

I think you are on to something. Looking at the rooftop shot of Jim B.'s new 5.0 it appears there is only one vent which would have to be for the black tank. Our early 19 does not have a rooftop vent for the gray tank, but it does have an overflow in the passenger side wheel well that also acts as a vent when draining. Never had a problem.

Mucram · 01-23-2018, 06:41 PM

Thought it was just the nature of the beast as never had grey/black tank before but the grey sure does take much time in emptying.

wetzk · 01-23-2018, 06:58 PM

Quote:

Originally Posted by Mike & Donna

Ours is like that as well. The black tank drains with a nice flow but the grey tanks flow is maybe 20% of that. Thought there might be an obstruction somewhere but we have always cleaned all food off the dishes before we wash them. Guess I should check the grey tank vent if there is one on the 2nd gen 19's.

Even though on our 19's the grey tank is right at the outlet the plumbing is smaller. And the black is elevated so it has that to help as well as larger pipes. I've never had it gurgle but it does take longer.
Only time that really bothers me is when 10 trailers are behind you waiting in line. Then it seems each minute waiting is a hour.

Mike & Donna · 01-23-2018, 07:05 PM

Ours is like that as well. The black tank drains with a nice flow but the grey tanks flow is maybe 20% of that. Thought there might be an obstruction somewhere but we have always cleaned all food off the dishes before we wash them. Guess I should check the grey tank vent if there is one on the 2nd gen 19's.

wetzk · 01-23-2018, 07:12 PM

Quote:

Originally Posted by Mike & Donna

Ours is like that as well. The black tank drains with a nice flow but the grey tanks flow is maybe 20% of that. Thought there might be an obstruction somewhere but we have always cleaned all food off the dishes before we wash them. Guess I should check the grey tank vent if there is one on the 2nd gen 19's.

Now how did my post that quoted yours post first?
OK Iowa Dave you messing with the that black hole and causing gravitational time dilation problems again?

richardr · 01-23-2018, 07:43 PM

When dumping we run the passengers side of the trailer up on our tire changing ramp to tip the trailer slightly and allow the gray tank to drain faster.

Ron in BC · 01-23-2018, 09:35 PM

Quote:

Originally Posted by richardr

When dumping we run the passengers side of the trailer up on our tire changing ramp to tip the trailer slightly and allow the gray tank to drain faster.

We've done that also. I'm always glad to see pavement that slopes towards the drain at dumpsites.

The reason that it slows towards the end is that the exit is at the side of the tank and the cross-sectional area available diminishes as the level goes below the center of the drain. At the end the drain size is minuscule. Red X. At some point I usually say, "good enough".

Ron

Jim Bennett · 01-23-2018, 09:49 PM

I have a cheater vent directly behind the bath in my trailer.

Just the black tank vent on my roof. (well, a few other things too.

On edit, I see Dave already posted the top of my trailer, albeit the naked view. LOL

Ron in BC · 01-23-2018, 10:36 PM

Quote:

Originally Posted by Jim Bennett

I have a cheater vent directly behind the bath in my trailer.

I think that the function of the cheater vent in that location is to let the sink water drain freely without going glug-glug. (tech term)

If the basic plumbing style is the same between our trailers then I don't think that it assists with the free flow of water draining from the grey tank because, between it and the tank, is ETI's version of a trap. Red X. The shower drain empties into the center of it. If there's water in the trap then the cheater vent isn't assisting with the smooth draining of the grey tank.

Ron

rubicon327 · 01-24-2018, 09:58 AM

Quote:

Originally Posted by Ron in BC

I think that the function of the cheater vent in that location is to let the sink water drain freely without going glug-glug. (tech term)

If the basic plumbing style is the same between our trailers then I don't think that it assists with the free flow of water draining from the grey tank because, between it and the tank, is ETI's version of a trap. Red X. The shower drain empties into the center of it. If there's water in the trap then the cheater vent isn't assisting with the smooth draining of the grey tank.

Ron

I wonder if there would be a way to furnish a small vacuum relief valve on the inlet fitting right before it enters the gray tank. This would be downstream of any traps and should allow air to enter to displace the water when draining the tank.

www.homedepot.com/p/3-4-in-Lead-Free-Brass-Vacuum-Relief-Valve-3-4-LFN36M1/203804518

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