Over the last two months we have had a rotten smell coming out of our utility room. We know it is not our drier or our washing machine and there are no leaks around any of the connecting pipes. We have also checked the u-bend under the sink as well as the dishwasher outlet pipe and are mystified. A plumber who came out for over £100 could not figure it out and the smell does come and go. The toilet in the room next door water level drops as well and the plumbers solution was to flush the toilet and tell us there was no blockage. Before we have to spend a fortune again what can anyone suggest for me to check.

Stephen... couple questions. Is this basement bathroom on a sewage ejector? Is there a bathroom above this bathroom (or a kitchen)? Do you have more than one vent going out your roof? Do you find that the toilet water level drops every time you smell the smell? Finally, how long have you lived at the property? Get back tonight and we will see what we can do.

I know you said its not the washer, but some times the washer does not spin out all the water and that water stays in there and gets stagnet, I have this problem once in a while and I run the washer through a cycle with a cup of vinegar this does two things it gets rid of the smell and cleans out the washer nicely. Just an idea.

Hi, mass plumber 2008. Thank you for replying. We have a loo next to the utility room and we have noticed that the water level seems to drop when the smell is in the room. Also there is a bathroom directly above the downstairs toilet and utility room (on the 1st floor) with a toilet to the side of it. There are tiny extractor fans in both the utility room and the downstairs loo but we have replaced them as we thought they were not working but this did not seem to make any difference. Due to the location neither the utility room and loo have windows which is not helping the situation either. Any help would be greatly appreciated.

Hi Stephen... tricky issue, but let's try this to start... fill and drain washing machine and while it is draining stand next to the utility sink and see if smell occurs at any time during cycle (unless washer drains into the utility sink and then that would not be useful to us)... stay for entire drain cycle. Then fill and drain the washer again and during the drain cycle go into bathroom and see if the toilet bubbles... stay in bathroom for complete drain cycle.

Then, if that does not suggest something... go upstairs and fill the bathtub... then drain the tub and go downstairs and see if the utility sink or the toilet are bubbling.

If you observe bubbling or gurgling then your traps may be getting siphoned as a result of either improper vent/waste piping in walls, or a clogged vent. Of course, it could also be that you have a clogged drain if there is bubbling occurring... so could be any of these... maybe more... ;)

Anyway, try these things and get back to us. Let us know what happens.

BUT first I would try what Jack dandy has suggested...that sounds as good as any other possibility when it comes to these things.