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Eruption from gray tank
Had a nice long weekend at MCCC in Indio. Beautiful weather and great visit to Joshua Tree NP. One bus problem developed. When the washing machine drain pump engaged, we had a nasty gas erruption through the kitchen sink drain. Not just a burp, this was strong enough to blow the water from the p-trap. (Did I say “nasty”?) The washer drained fine otherwise. I assume this indicates blockage or partial blockage of the tank vent. I have noticed that the gray tank is slow to drain, which may also be an indicator. The vent pipe is not easy to get at because of other plumbing and mechanicals in the area. Before I start taking stuff apart, is it worth running a long snake down the vent pipe from the roof? Any risk of wrecking anything?
p.s.: Sid Tuls, I looked for you and saw your beautiful coach, but no one was home when I stopped by. You sure have a beautiful view from your site. Enjoy!
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3 Replies
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Bryan,
It should be an open vent, wouldn’t think you could damage anything by running a flexible “snake” down it. If the gray is draining slow, that’s a good indication of something blocked in the vent somewhere.
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Brian,
One sad fact is our coaches would likely fail to meet typical plumbing codes because the systems have to be designed to function in a coach, not a house. I am not familiar with how your coach was plumbed but if what you described happened in my coach I would expect something is inhibiting the venting as you surmise. The obvious first place to start is to make sure the vents that pentrate the roof are open. But because of your layout it is also likely you have what is called an “air admittance valve” because one of the fixtures such as the kitchen sink could not be equipped with a roof vent.
An air admittance valve is a spring loaded valve that closes when there is no flow via a spring so you do not introduce sewer smells into the coach. But as waste water is introduced into the drain it creates a slight vacuum which pulls the valve open to admit air into the drain lines. If that valve is stuck shut no air will be introduced. Look for it to terminate somewhere in the sink cabinet up high such as near where the faucet pipes come through the counter top.
It is conceivable your washing machine could have one also.
For your gray water to drain slow your drains may not have adequate venting and how your washer bubbles into the sink might be the sign of that condition.
Air admittance valves are typically used where you cannot vent a drain to atmosphere such as in a kitchen with a sink in an island. But they are generally prohibited in most plumbing codes.
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Thanks Jon and Jerry. I checked for those under-sink valves and don’t seem to have any. I know that on my Country Coach Prevost I had to replace them every few years to stop backflow of odors. It is possible there is one for the the washer, but in my experience they will fail to close when they age, as opposed to getting stuck closed. Still, a good thing to check. I’ll have to pull the washer from the cabinet. In the meantime, I’m going to try the lazy man’s way and will send a snake down from the roof.
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