Mobile Home Drain Line Venting

Manufactured home drain line venting

Venting is one of the areas where mobile homes differ from site built homes. In site built homes every drain has a vent pipe that eventually goes up through the roof. The purpose is to prevent the siphon effect of water going down the drain from pulling all the water out of the trap. In mobile homes venting is frequently accomplished with one way air valves that will be located under the sink.

If the valve fails you may smell sewer gas inside the home because it is no longer blocked by water in the trap. The valve may be threaded and easily unscrewed for replacement or glued on and you will have to cut the line to replace the valve.

{ 2 comments… read them below }
Hi! We have a Kenmore dishwasher in our kitchen and a couple of months ago it stopped working and seemed to not be draining correctly. We dried up all the excess standing water inside the dishwasher and now it smells horrible under the kitchen sink. Do you think the dishwasher is to blame or do we need to replace the air valves? (The dishwasher is located right next to the kitchen sink and cabinets). Thanks!

The kitchen sink is still draining properly? Can you tell if the dishwasher empties at full force into the drain line and ss blocked there, or does it not drain well because of stuff stuck in the bottom of the dishwasher?

The vent caps are cheap so it would be easy enough to try a new one and see if it makes a difference

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  • hello . im kind of confused . we took out a garden tub in the bath room and now drain in shower running slow . but i have a vent pipe under the cabinet and the shower has its vent pipe out the roof . and the toilet sit beside the garden tub and we took out garden tub and closed off all pipes under garden tub, could any one tell me what we did wrong , thank u

  • Hi Jessie,

    Slow drains in a bathroom shower are almost always caused by hair getting stuck and accumulating.

    Try bending a small hook onto the end of a stiff piece of wire (like a coat hanger) and pushing that down into the drain. Paull it out and repeat until it doesn’t bring up any more hair.

    That may or may not work, but its free and worth a try.