Good Sam Club Open Roads Forum: Black Tank Roof Vent and Bathroom Roof Vent Too Close?
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 > Black Tank Roof Vent and Bathroom Roof Vent Too Close?

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BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

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Posted: 07/03/20 11:29am Link  |  Quote  |  Print  |  Notify Moderator

I now see that the grey drains do not go into the black tank at all, so the black is all on its own. Not sure how the sinks and shower drains are vented. Double kitchen sink so that might be it for there if you don't plug both. Bathroom shower could vent via bathroom sink not plugged. No air admittance valves anywhere in the pipes past the Ptraps. (1991 RV)

Good idea for a shower drain plug. You have to stand in the shower pan while at the bathroom sink. This is not a 5er! [emoticon]

Got the drains all cleaned out so have to do a smell test later. The black tank is all cleaned out too so be a while before any tests.

I have to rig a second tank under the TC overhang behind the truck bumper to be the grey tank. I did that before with our previous TC. Fairly simple job where it can be hanged from above and supported below with a towing piece in the receiver with a plank over to the side attached using the hole where the ball normally goes. Just have a short hose that goes from the sani-cap down to the grey tank. A tap to dump it if it doesn't have one.

A plastic bigger gasoline can works for that if on it side. Its pouring hole on top to take the grey filling hose, and leave its vent screw- on cap at the bottom to be unscrewed as the drain. Good enough for sinks, but not big enough for shower of course.


1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
See Profile for House electronics set-up.
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas

ajriding

st clair

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Joined: 12/28/2004

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Posted: 07/04/20 08:33am Link  |  Quote  |  Print  |  Notify Moderator

The sink may not have a vent. Sometimes the sink will have a one-way air valve so when water drains down from the sink it can pull air into the pipe and not suck water out of the p-trap, but possible it has nothing. Otherwsie it should have a vent pipe connected to the roof vent pipe.
The black and gray tank's vent pipe might connect together before exiting the roof, so if you just have one vent stack on the roof then they are connected, not a problem. They would be connected as high as possible, and odors should not rise from the black up to the connection and then back down the gray into the cabin. The gray pipes are all blocked of by water in the p-trap, so after a drive make sure there is still enough water in the traps (sink drain) to block off airflow.
It is possible the water gets sloshed out of the trap enough that air can get by, and just 2 seconds of running water in the sink will fill it back.
Also, if the wind blows really hard and the trap is empty then possible odors swirl around in the vent stack and move back down...
In a double sink only one drain might have a trap, not both, only one is all it needs to block air from the gray tank, not so much the pipe. The first drain flows into the second drain pipe then into one p-trap. The p-trap could be down stream a few more inches than normal if the camper cabinet is tight on space...
You should not need a drain plug, the p-trap will do the job.
Some people have worse smelling poop than others also, some have very unhealthy guts, and not much the camper system can do about that. Try to not use the bathroom in camper if you can help it.

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