Smelly bathroom drains

[billengr]

We have a shower and hand basin feeding to an P trap under the floor. We can see into the top of the P trap through an unscewable round grill which i suppose is there to drain floor if sink overflows. There is a horrible musty mouldy smell comming from there. Not a sewerage smell- P trap is always full. Disinfectant doesn’t work, nor draino. I have to unscrew grill in floor and the one in the shower, block the P trap, then fill it with 1 litre chlorine and water and let it bubble away for 30 mins. Ok for 2 weeks then bad again. What is IT? Other upstairs bathroom and downstairs OK

[Retired plbg1Participant]

The way it sounds to me is that you have two fix. on one trap and the pipe going to the lav. is making the smell. Best way is to take lav. out and connect it up right according to code with a vent and plug the openning going to shower trap and it should be solved. Do you have trap on Lav.

[jontonParticipant]

Thanks plbg. I haven’t been here before and am quite impressed to find such a site. Ok, pipes all look pretty legal. Hand basin has an S bend in the cupboard beneath it, then goes down to tee into the hole in the floor. Shower has no P trap, just goes down and across to tee into same hole in floor. Then hole, shower, and basin water all pass thru a P trap, then go outside to turn downwards and join into a 4″ pipe. Toilet has an S bend then outside-this IS the 4″ pipe. All joined together now, with a vent right there, then go down into ground. Doesn’t smell like sewer, just mouldy musty and quite strong. Did a search here yesterday after posting and found two other similar cases were advised soap fat and hair grow the bugs that smell. Use vinigar and maybe baking soda. Tried these already, chlorine works better for me. But there must be a permanent fix. Other showers are permanently Ok. I was thinking remove and plug pipes and pee out window.

[Retired plbg1Participant]

You need to take out the s-trap under lav. and run pipe up through roof and stub out a arm with a p-trap for lav.
You need a p-trap on shower with a vent. All that pipe you have installed has body waste in it and you get the smell, so take out all pipe to last connection and redo it and vent it and you will not have anymore trouble. All fix. require there own p-trap.

[Author]

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