Sewage smell in kitchen - help!

[fosterdog]

For the past week or so, a faint smell of sewage has appeared in our kitchen at night, often starting at about 9pm. It tends to clear up by mid morning before returning the next evening.

It doesn't seem to be coming from any of the drains. I've checked under the cabinets and there's no visible leak. I've also lifted a floorboard and it smells fine under the house.

I think it might be coming from the edge of the concrete floor of our small (c 2m) kitchen extension. There's a small hole at one point between the bottom of the side wall and the plastic membrane up the side of the concrete.

A sewer pipe runs under that extension, along the back of all the houses in the street.

However, checking whether that sewer has cracked would involve ripping up the concrete floor and excavating the kitchen.

I'm only 50% sure that is where the smell is coming from. So spending thousands investigating this is scary.

The concrete floor itself was new last year, replacing the previous uninsulated concrete floor. There's also a new patio at the side of the house in line with the sewer's path. I wonder if digging up the previous floor/patio might have disturbed the sewer, but it seems odd that the smell would have taken 10-12 months to appear after the work was done.

Finally, we have a new kitchen arriving in 2 months so we need to get this all sorted quickly.

What sort of tradesman would investigate this sort of thing?

Help!

Many drainage companies have CCTV equipment which they can push up / down drains to.inspect from the inside.

Not sure what the cost would be but surely cheaper than digging up the whole floor on the off chance there's a leak in a small section.

Used to live in an old house with occasional short lived unpleasant sewer drain smelling kitchen
Because the smell used to cunningly vanish as quickly as it came we were despairing too.
Finally DP put some really strong drain cleaner down the sink & waste. This then solved the problem for many months till next occurrence.

Sadly I have no idea what was used and this was some years ago but must be worth a shot before splashing out big money.

Thanks. We've tried the drain unblocker approach. The drains all smell fine. It's coming from somewhere else.

Definitely get Dyno-rod or similar to come out and ask for the cameras.

You can check whether there’s a crack in the drain under your extension or not and hopefully rule that out.

Even when there is a crack found there’s a thing they can do called “sleeveing” where a new, slightly thinner in diameter, pipe can be run through the old one so you don’t necessarily need to dig up the extension floor.