24 Jun 2021
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United Kingdom
Hi everyone,
I am having a problem with my wet room drain, it’s air locking. If you pump it few times, the water drains, leave it few minutes and turn the water on again and it stops draining. I was advised it is air lock and it needs an AAV valve, the problem is it’s a wet room with linear drain so where to put the aav ? Also, there is an AAV valve on the stack that serve the sink, toilet and the shower. We had the bathroom fitted about 4years ago and just recently we started having this problem.any advice will be greatly appreciated
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After 4yrs use I`d suspect a partial blockage in the pipework.
I managed to put drain snake through and no blockage , also used one shot and drain descaler twice and used vacuum as well, the pipe is clear 100% and that’s what makes me think there is air block
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Replaced it even though the old one wasn’t faulty
My mate had a slow draining shower so he bought some stuff to pour down it. He thought he’d do it when he came home from the pub and his wife was in bed. Unfortunately, she did the same thing with a different product before going to bed. Neither of them told each other of their plans. He came home, put the stuff down, a "load of smoke" billowed up and gassed him. He just about woke his wife and had to be taken to hospital for treatment.
The same thing happened to me many years ago when I use some One shot, I asked the customer if anything had gone down the drain and got the normal answer of No. One shot and bleach make a very nasty chemical which nearly gassed me. I was hanging out of the window trying to breathe. I haven't used One shot for many years.

Thanks guys for your comments, I didn’t use one shot and other chemicals in the same time , I followed every precaution. the problem I have is slow drain and once you pump it up with pump plunger it bubbles and then drains very nicely. Once the water turned off and then on again after few minutes, it doesn’t drain.. really puzzling.. that’s why I am thinking air lock.. I could be completely wrong.. please correct me before I take the ceiling down
A builder mate of mine once told me he had used a particularly strong drain cleaner (one shot?) that he left in for too long and it had melted the waste pipe so much that it had sagged between the joists.
Try taking the AAV off temporarily and see if the shower drains normally. If it does then you need a vent on that branch... Air needs to be allowed out as well as in on certain branches.
If it worked fine before and now doesn't then it can only be a pipework issue or a restriction somewhere.

A waste system won't just start airlocking for no reason. Try taking the AAV off as suggested by @dilalio as see if that alleviates it, if it does then there may be an issue with a slow draining stack and your getting back pressure, if not then the only way to get to the bottom of it is to start at the drain and work your way back along the waste run to the stack unit you find the issue.
You are right, it can’t starts air locking if it worked before. But how would you explain it, no obstruction as I borrowed a k45 machine and put the snake through until it appeared in the stack so the pipe is 100% clear. I think it could be the one shot I put and it damaged the pipe or it caused it to dip somehow so when air is introduced by the pump action, it flows freely. I am thinking of taking the floor up and replace the drain pipe

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