Gurgling sound coming from my tub and sink drain

Question

I have a gurgling sound coming from my shower drain and from the bathroom sink after I run some water.

It sounds like air coming up and something that would happen when the air vent to the gray tank is stopped up, but I have used a garden hose and run water down through the vent pipe that's on top of the RV and watched it come out of the drain. I get the same sound even with the gray water tank drain open.

Does anyone have any idea about what's causing this and how to fix it? It's not big deal, but it tells me that something is wrong.

It sounds like a simple problem. Water is going into the gray tank and the air has to come out somewhere. If there is no way for air to get out of the tank, then the pressure causes the air to gurgle up through the tub and sink drain. The only problem is that there seems to be a working vent to the gray water tank.

newman_fulltime · Answer

Look under the sinks you should see a vacume breaker on avent pipe.sounds like it has went bad

jerry8mm · Answer

Thanks. I do see it and I see that it has threads. So I guess it just unscrews, but since I have company coming for Thanksgiving, I don't think I will unscrew it and take a chance on having plumbing problems over Thanksgiving.

At least, I know what to work on next week. It make sense that that could be the problem.

wa8yxm · Answer

I think those sounds are more or less common in RV's. what may be happening is this. For this discussion I will describe MY RV.

The kitchen sink drains into a line that goes across under the Floor (heated bay) to a T fitting where the bathroom lav T's in and then on to the gray tank

Water rushing past the "T" is sucking air in, just like air rushing through a carb sucks gasoline. This causes Gurgle if the air admittance valve does not open. Not really a problem.

clay_l · Answer

jerry8mm wrote:Thanks. I do see it and I see that it has threads. So I guess it just unscrews, but since I have company coming for Thanksgiving, I don't think I will unscrew it and take a chance on having plumbing problems over Thanksgiving. At least, I know what to work on next week. It make sense that that could be the problem.They (air admittance valves) do unscrew and once off they can be checked to see if the flap moves freely. The ones I have removed over the years were hand tight and pretty easy to take off and replace.Many hardware stores have replacement units.

jerry8mm · Answer

Thanks Clay,I'm going to give it a try on Monday (as soon as company leaves and Thanksgiving is over with).

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Gurgling sound coming from my tub and sink drain

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