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Old 04-11-2018, 05:08 AM   #1
1 Rivet Member
1974 31' Sovereign
Crested Butte , Colorado
Join Date: Apr 2018
Posts: 11
2 grey vents?

My 1974 Sovereign has 3 plumbing vents on the roof. 1 for the black tank and 2 for the grey. 1 of the grey tank vents is forward and connected to the kitchen sink drain pipe the other is for the tank. I donít understand why there would be 2? Does anyone know?
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Old 04-11-2018, 05:30 AM   #2
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1994 30' Excella
Mississauga , Ontario
Join Date: Jun 2004
Posts: 1,010
Forward one is to vent the sink drain pipe. If you didn't have it you might get a siphoning action which would suck the water out of the sink trap allowing sewer gas into the trailer.
Al and Jean

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Old 04-11-2018, 06:15 AM   #3
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1955 22' Safari
1967 26' Overlander
1955 22' Flying Cloud
Clear Lake Shores , Texas
Join Date: Nov 2013
Posts: 1,342
My 67 Overlander is set up the same way.
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Old 04-11-2018, 07:40 PM   #4
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1986 34' Limited
1975 27' Overlander
Conifer , Colorado
Join Date: Jun 2009
Posts: 6,131
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Same same on my 75 Overlander. I wonder if there is some relation to the length of the drain run to the tank that would call for two (actually 3 gray water vents in my trailer). There are new "air emitter" devices that can be plumbed in downstream of the trap that open if they get any vacuum in the line. Some folks call the "vacuum breakers". These are easier than running another vent line.

Here is a photo of the drain plumbing in my Overlander behind the tub. The two pipes going to the bath wall tee together and up through the roof. One was bath sink and one was shower drain. The other vent line is forward in the galley wall and up through the roof.

No excuse for a gurgling drain in this Overlander.

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