Bad Smell in Downstairs toilet

cdixon

I have a problem with a bad smell in a downstairs toilet (and upstairs toilet) for a couple of years now. I have had a number of different people look at it without success (2 x Plumbers, Builder, Man from council, 2 x Drain Companies) The main problem in finding the cause is that it is an intermittent problem. There is a faint smell sometimes but the major issue is a really pungent smell (Gaslike) when it rains after it has been dry for a few days. Does anyone have experience of a problem like this ? Or can refer me to an expert ?

li@mo

Are you using a septic tank or mains sewer connection?

Poor Uncle Tom

Very good question [EMAIL="li@mo"]li@mo[/EMAIL], it seems to be an issue with ventilating your system properly, if its a septic tank ststem. Or if its a mains system its probably a combined system. When it rains the volume of water in the drains will pull the trap from your toilet allowing the sewer gasses to enter the house. Probably needs another SVP or BIGT between the house and sewer pipe.

Note: If yours is a septic tank system, rainwater should not be combined with sewerage going to the tank.

Get an AT to have a look at it for you, remember we design the workings of these systems.

RKQ

Sounds like a loss of seal / water trap to wc or whb resulting in gas from sewer pipe entering room. Extraction / ventilation of the sewer pipe is required.

Get an Architectural Technician to inspect your system. In the meantime flush your wc regularly and run the taps in the whb to maintain a water seal.

cdixon

Thanks Lads,
Mains Sewage for sure, I think it's a combined system. The toilet water trap is still in place when smell is really bad in both downstairs and upstairs. How would the extra water in the drains pull the water from the toilet out ? Thanks for tip on AT. I had no idea who to contact.
Also I'm fairly sure it doesn't happen every time it rains or maybe it just doesn't get unbearable until there has been a dry spell before rain ?

Poor Uncle Tom

In a combined system the flash of water to the drains in heavy rains can cause low pressure or suction behind the flow to pull the water trap from the toilet. The WHB's usually empty to a hopper for the first floor and to a GT for the ground floor so they are not usually affected by the pressures in the drain.

If the water trap remains in the toilet, do you ever hear it bubble or gurgle? Either way I feel you could do with extra ventilation (SVP) on your drainage system. You should get it looked at.

cdixon

Thanks. I have some emails out for an AT. I have had a builder, 2 plumbers, 2 Drain Companies and SDCC already in the last few years !!!

Heatherview

Hi cDixon
See attached sketch. Took a good while to figure this one out but it fixed it. My experience check it out on your system
Hatherview

cdixon

Sorry Heatherview,
Not sure I understand fully what the work was. Not too familiar with the whole thing I'm afraid. Did you repair the multiwick ?
Also not sure how does this explain the problem only ocurring after rain ?

mickdw

I would think its the water seal being sucked from the whb. You say toilet seal is always there so its not that. You could fit an air admittance valve in the system. This is a one way valve so it will allw air into the system instead of the system pulling the water from the traps