Advice: buying a property with an internal manhole / drains

Hi All,
Is anybody living in a property in the Forest Hill area which have drains and a manhole internally? What are the issues faced and if buying with the above mentioned would you pursue the property. Any advice would be very much appreciated. Any advice on this matter would be so helpful to us to be able to make an informed choice.
Whether this is a deal breaker.

Thank you!

I have a drain in my conservatory. Leaves and other debris come down the drainpipe. I need to keep the drain clear otherwise there will be some floodwater in my conservatory.

If there is a manhole cover, it should be relatively easy to rod the drain. I think a manhole cover is usually placed whenever there is a change of direction in the drain.

Manhole covers in an extension are quite normal. Depends if it’s foul water or not.

I wouldn’t worry about an internal manhole. We put one in our old flat when we built an extension over the inspection cover. It is pretty rare to get a drain blockage so we simply had our floorer cut a rectangle above the manhole that we then put back in place and filled the gap around the edges with caulk. It never blocked, so we never had to disturb it, and you could barely see there was an issue.

Hi Sherwood,

Thank you for your quick response and information stated very helpful. The reason for asking the question is Thames Water have stated that they would have issues with a internal manhole, due to the smell and gaining access. Especially when the drains and manhole services the next door property. What concern us should anything goes wrong with the next door they need to gain access via the property which we ar3 intending to purchase.

Thanks again.

Hi there,

Thank you for your very informative feedback we have noted all what you have stated.

Thank you!

Hi Londondrz,

Thank you very much indeed for your response very much appreciated. We found your response very helpful and informative.

Thank you very much!

It shouldn’t smell if properly sealed.

PS: you can just heart my post rather than send a formal thank you!


Our drain is in our patio, and it has blocked once. It serves our neighbour’s property, and I think they were flushing wipes down the toilet. The manhole cover is concrete and very solid and heavy, and seems to fit into the hole very well, but I’d be worried about the smell. And how do you access it internally?

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A manhole inside a property should be both accessible (for obvious reasons) and also have a “double-sealed” cover. The double seal element is intended to prevent foul air escaping into the property.

You describe your cover as being concrete with a tight fit and it therefore is unlikely to be double seal - so for the mean time as long as there is no smell - leave well alone. If smell does become an issue you could replace the cover with a double seal variant.

A few years ago Thames Water issued every household with new diagrams that gave typical layouts for shared drainage systems with a set of re-defined responsibilities and obligations.

In the configuration you describe with the drain serving your neighbour’s property, the clearing of any blockages are specifically the responsibility of Thames Water.


Thanks, and it’s good to know, but I’d be interested to know how quickly Thames Water would respond, given my pretty bad track record dealing with them.

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For a problem with a commonly shared drain in my neighbour’s garden a few years ago, after they received the call, Thames Water’s inspector arrived reasonably quickly.

It went wrong from there. He turned up when no-one was in, drew the wrong conclusions but did actually instruct his contractors to attend. Contractor duly turned up but declared he could not raise the double seal cover and left site.

On returning later that day I released the cover after a few minutes effort and got hold of the inspector once more and pointed out to him that TW had to do better and that we needed a gully sucker to clear the surcharge and remove the blockage.

He was a bit miffed, returned to site pdq and then ordered the gully sucker. Overall there was about 26 hours wasted.

So prompt response when there is an emergency but a close eye is needed on their actions and proposals.

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