Why does one bathroom sink stink and the other doesn’t?

gary-736Dear Gary,
I have two bathroom sinks in my coach: one with the commode and one next to the shower. The one in the hallway of the coach has a terrible smell. It is not all the time, but I cannot pin-point what is causing it. This has been going on for a few years now. I have poured the stuff that takes away smell down there and even used apple cider vinegar. Nothing seems to work. It is just that one drain. Any suggestions? —Kathy P.

Dear Kathy,
Chances are you have a faulty anti-siphon trap vent device (ASTVD) under that sink. It’s a small ABS plastic fitting found near the P-traps under most RV sinks. Its purpose is to allow air into the drain system to help drain the sink, at the same time it prohibits gases and odors from coming in from the holding tank and drain piping. It is constructed with a spring-loaded rubber diaphragm. Oftentimes this rubber membrane will dry out and not fully seal against the rising odors out of the waste system. Other times, the spring simply wears out.

If you look under your sink and follow the horizontal ABS piping as it leaves the P-trap, you’ll likely find the ASTVD situated a few inches above this horizontal arm. It’s a simple, screw-on fitting. In some cases, the rubber membrane can be renewed by applying a lubricating grease; I recommend Dow 111 grease. It’s a relatively inexpensive component and is easily replaced by any RV handyperson since it does not require any sealant and is only hand-tightened in place. They can be purchased or ordered through any RV parts department or even online.

Another thing to consider, especially if you need a little more room under those sinks, is to replace all the P-traps with a HepvO waterless sanitary valve. When using a HepvO valve, an ASTVD is not needed at all. Plus there is zero maintenance (no winterizing, cleaning, etc.), when using a HepvO valve. But one of the biggest benefits is the added storage space under the sinks. This is the route I highly recommend! Read all about the HepvO waterless sanitary valve.

And here’s a short video I produced regarding the HepvO valve. You’ll also find more helpful information at the Drain Master website.

Hope this helps! At least it will keep you busy for a while!

Read more from Gary Bunzer at the RVdoctor.com. See Gary’s videos about RV repair and maintenance.



8 Thoughts to “Why does one bathroom sink stink and the other doesn’t?”

  1. John Tasselmyer

    My ‘sink smell’ originated from my water system. My plumbing has a dead leg for the hot and cold water to the uninstalled washer option. When this stagnant water remains it can add smell to my bathroom sink water. Flushing/sanitizing these lines eliminates the odor.

  2. Drew

    I simply taped over the vent hole in the device…no more smells and no other issues either. I had previously greased the rubber diaphragm which didn’t work, then finally replaced it which didn’t work either.

  3. Gary McLachlan

    We have just rediscovered you and subscribed. You are answering our needs. Thank you so much. Gary and Nancy McLachlan

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  4. Charlotte

    We bought our replacement trap at home depot. We needed it for the kitchen sink but after buying it could not get to it. It was situated way back in the corner. After having it a couple years when the RV repair guy was here replacing the hot water tank, he was skinny enough to reach back and put it on.

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