Fosse - The dreaded Word - Help!

We have a problem with smell in bathrooms from new Fosse installed 18 months ago. The Builder says not his problem!!! We have two vents including a spinning vent on the roof, but still have a smell in the bathrooms!! There has been this problem since it was installed which was sorted temporarily by a 'u' pipe being put into the tank to stop the smell backing up into the house. That has now stopped working! Various people have been round and looked and cannot find out why. Could somebody please advise who we go to to get an independent review, which doesn't cost the earth, so that we can go back to the installer and get them to put it right. We are thinking of gong to SPANC but not sure if that is the first port of call. Any suggestions would be appreciated!!! Also language a major problem as it is all technical!!! But hopefully have a translator we can use....... Thanks

Does your fosse have an aeration duct? This is usually a plastic tube of around 10 cm diameter that sorts from the main evacuation pipe leading to the fosse and rising up well at the height of your roof-sink. Older fosses might not have had this feature, but the newer systems require one. This is btw not the smaller vent-duct(s) that come on top of these modern fosse-systems.

Every time you flush the toilet the content of the bowl, together with a lot of air, is rushed down the evacuation pipe into the fosse-system. This leads to a pressure difference and a resulting, momentarily break of the toilet's (or any for that matter) water-seal allowing some of the gasses that normally accumulate behind that seal to rise up through the bowl. The aeration pipe reduces that pressure difference.

These pipes can be fitted with a unit that will neutralize eventual bad smells that are liberated in an aeration pipe

Check this pic for the "conduite eaux vannes" and "aeration"

I had a similar problem in a house I worked at for a while. After many many searches I eventually found 2 problems, one there was an uncapped pipe under a bath and the second was a perished seal between the toilet exit and the pipe. The uncapped pipe was in a cellar but up near the ceiling when that was capped we thought the problem had gone. The smell was still there a week later, though not as bad it was then we found the toilet seal perished.

Are you absolutely certain the vent pipes are connected? at the fosse end. If you internet search fosse septique you can see a schematic diagram of where the pipes should connect to in the type of system you have.

Good luck

this is what we do in the bathrooms that arn't used all the time and that solves it for us

turning into a real mystery this one - are there any outlets that have u-bends but that aren't used often (so the water stagnates in the u-bend) as this ends up producing the same smell. an extra waste pipe for a washing machine in the bathroom etc. If there are any that aren't used flush a load of water through the u-bend: that'll replace any old stagnant water and fill any u-bends that have dried out/water has evaporated and so no longer provide a seal.

if only… Nope no gas…

is it the fosse - have you got gas or bottled gas in the house?

Hi, U-bends on all sinks, etc. Showers do not have u-bend but traps have water in them. Everything drains away quickly. Smell hangs in the air and is a gas smell rather than sewage smell. It doesnt seem to come from anywhere in particular, just kind of ‘hangs’ there. Will check no blockage but currently no-one to help. Thanks.

have you got u-bends on everything - sink, shower, bath, washing machine, dishwasher etc. easy to check and quick to fix.

Where exactly is the smell coming from - try and locate it to give us a better idea ;-)

Does everything drain away at a reasonable speed - loo, sink, shower, bath etc

lift the lid on the fosse and get someone to flush the loo - does it come straight into the fosse or is there a blockage (the u-bend you talked about) between the house and the fosse...