Rats - one way valve

cjmc24

We had an extension built about 6 months ago, and over the past few months we have heart loud noises (stretching etc) in our lounge ceiling and walls. To cut a long story short we have had numerous pest company round and have recently had a drain survey, which we think shows a slight hole in one of the connections from the old drains to the new drains. When we did the extension we needed a build over agreement from Thames water which is al fine, but essentially now the original drain is under our kitchen island! One of the suggestions the drain company had was putting a one way valve in to our drain, which we have done in our neighbours manhole. Unfortunately it hasn’t stopped the issue completely. We have our builders coming back this week to take up our kitchen floor and repair any damage they might find (which I sort of hope they do, because at least we know where it’s coming from!) but whilst they are there we were thinking of asking them to install another one way valve at our original manhole. Obviously the only issue is maintenance of that valve, as it will be under the island again? Has anyone got any suggestions? Do you think it needs maintaining? Should mention our new drain access has been moved to our patio, but it isn’t the original manhole so doesn’t help in terms of adding a valve there as there are about 5 houses the other side of us to the neighbours where the valve has been installed.

cjmc24

Also should mention we know which way the drains run to the sewer which is why we had the valve installed on that side, but they’re obviously getting in another way!

Apodemus

Sounds to me like you are fixating on rats coming from the drains, rather than finding the true source of the noise!  Did the pest control companies actually find evidence of rat infestation - droppings, gnawing marks?  Even if it is rats, how do you think they are getting from the drains into your ceiling space?  Much more common for rats to have a more direct method of entry.  Mice are probably more likely than rats and even a single mouse can make a surprising amount of noise despite its small size.  You don't say what is above the ceiling in question - if it is just roof space, another culprit could be squirrels or birds.   

...and in my experience, drain companies will always find slight imperfections that need additional works!    

cjmc24

Thank you! So they found droppings in our drains - I should have also mentioned over the past few weeks we have started to smell a sewage smell in a kitchen now and again, those 2 things make us think its worth just checking the drains in case it is an obvious fix.
If it isn't the drains - then we have run out of other ideas! We had the house completely re done at the beginning of the year, stripped back to outside walls, so all the internal walls are new, an extension, a loft conversion, and the house repointed, so definitely no holes on the outside walls, so I cant honestly see how there's another way something would be getting in?
The only other thing we can think of is it's coming in from next door (we are a Victorian Terrace) but if it is, it must be under the foundations, and I cant see how that would happen either. They haven't heard anything in their house?
I'm open to ideas though, it's driving me insane (as you can probably tell, I have become a bit obsessive about the whole thing!)
You're also probably right about the drain company, we have spent almost £2,000 with different companies, and I think they feel they HAVE to find a problem!

Alter_ego

If from next door, via the loft is more likely.

cjmc24

Thanks, we've had our loft converted and so have they?

Apodemus

As you say, it is difficult not to come to the conclusion that the drains are the problem.  However, you have more faith than I would that the recent builders have left no gaps in the structure, either to the outside or to the neighbours!  I've had previous experience of trying to keep rodents both in and out and they'll outwit the best laid plans, even when pest-proofing is uppermost in the design!

naf123

Do you have service drains/gulleys? Have you ever seen rats outside your home?

TC77

Interested in how you are getting on. I've  a nightmare with scratching from rats in the wall and ceiling of the extension. Wondered if I put a one way valve in then the rats can go out but can they stay in the house a while before deciding to leave? How long before I know if it's worked?
Thanks