Would you buy a house with an internal manhole and drainage issues?

mame_is_me

Hi everyone,

My partner and I are currently in the process buying a house we really love, but there are concerns and we would really appreciate people’s thoughts—especially anyone experienced with drainage or buying homes with legacy work.

Key Findings

1. There’s an internal manhole that ended up inside after an extension in the early 2000s (no build-over agreement).
2. Drainage searches came back clean, CCTV showed drains are private, but it also showed:

• The internal manhole is untrapped, so could vent foul smells.
• Downstream is blocked and leads to another manhole outside which is currently inaccessible.
• The report advises installing a trap and making the outside manhole accessible before exchange.
• The pipework is combined foul + surface water and has several blind junctions. 

Our concerns 

1. Even with a trap, internal manholes seem risky—if something blocks in future, would we need to dig up the kitchen?
2. Could heavy rain or backflow cause flooding inside?
3. Combined drainage feels riskier vs modern separated systems—are we overthinking this?
4. Would this affect resale value?

Are our concerns valid, or are we catastrophizing something that’s fairly common and manageable?

If it were you, would you still buy the place knowing this? 

twopenny

You had me at 1. 
Definite no from me.

That is unless you have a goodly sum put aside and good contacts.

mame_is_me

twopenny said:

You had me at 1. 
Definite no from me.

That is unless you have a goodly sum put aside and good contacts.

Thanks — have you come across internal manholes yourself? I know they haven’t been allowed since 2011, but I’m curious how many older/legacy ones are still around.

Eldi_Dos

Your concerns are valid but there will be many properties with similar arrangement that never give any proplems.

Have you actually seen the CCTV yourself to see existing pipework and while in the property where any smells noticeable?

Keithy13

We had an extension built (extra bedroom and en-suite) in the early 1990's. There was a manhole where the en-suite was going. It was double sealed and signed off by building inspectors.
So more than 30 years ago and there has never been any issues with it.

Tiglet2

A friend of mine had an internal manhole in her kitchen (which had been extended into the garden by the previous owner).  The manhole was under some cupboards, so was extremely difficult to get to.  Of course, a couple of years later they noticed a drain smell in the kitchen and had to rectify it.  I believe there was some leakage into the kitchen from a broken pipe.  All I remember was that it took a long time to get it all sorted, cost a lot of money and there was enormous disruption in the kitchen while cupboards and the floor were dug up etc.  They moved about a year later, but it didn't affect the resale value as the problems had been rectified.

Another friend had one in her conservatory.  Even this can be problematical but in her case the entrance of the manhole was accessible and had been correctly fitted and up to the current regulations at the time.  She had placed a rug over it to disguise that it was there and I don't remember it ever being a problem.

Having said that, I wouldn't buy a property with an internal manhole if I could afford not to.  But this is your decision.  You could go back to the vendors to request that they install a trap and make the outside manhole accessible before exchange, though they may do a poor job very cheaply by a mate of a mate, or request a reduction in purchase price so that you can do the work after completion and to a better standard.

theartfullodger

As ALWAYS with property prices, if the price is right obviously yes.  Sigh!

Albermarle

We have one following a side extension in 1999.
It is under a carpet.
I did notice a very slight whiff ( or thought I did) to begin with . I lifted the carpet and underlay and put a plastic sheet over it and relaid the carpet and never been a problem since.
There is another manhole in the driveway, so if there were ever any problems hopefully they could be dealt with from there.
I would not call it a deal breaker, if everything else is OK. 

mame_is_me

Eldi_Dos said:

Your concerns are valid but there will be many properties with similar arrangement that never give any proplems.

Have you actually seen the CCTV yourself to see existing pipework and while in the property where any smells noticeable?

Yes, we’ve seen the CCTV report and some of the footage, and we didn’t notice any smells during our visits — if we had, we wouldn’t have proceeded. 

If there’s a manhole already in the house you’re living in, it seems acceptable as it often doesn’t cause major issues. But if you were buying a house today, would you personally go for one with an internal manhole and possible drainage issues, or is it a dealbreaker for you?

mame_is_me

Tiglet2 said:

A friend of mine had an internal manhole in her kitchen (which had been extended into the garden by the previous owner).  The manhole was under some cupboards, so was extremely difficult to get to.  Of course, a couple of years later they noticed a drain smell in the kitchen and had to rectify it.  I believe there was some leakage into the kitchen from a broken pipe.  All I remember was that it took a long time to get it all sorted, cost a lot of money and there was enormous disruption in the kitchen while cupboards and the floor were dug up etc.  They moved about a year later, but it didn't affect the resale value as the problems had been rectified.

Another friend had one in her conservatory.  Even this can be problematical but in her case the entrance of the manhole was accessible and had been correctly fitted and up to the current regulations at the time.  She had placed a rug over it to disguise that it was there and I don't remember it ever being a problem.

Having said that, I wouldn't buy a property with an internal manhole if I could afford not to.  But this is your decision.  You could go back to the vendors to request that they install a trap and make the outside manhole accessible before exchange, though they may do a poor job very cheaply by a mate of a mate, or request a reduction in purchase price so that you can do the work after completion and to a better standard.

Thanks a lot for sharing this. 

stuart45

I wouldn't put an interceptor trap on an internal manhole. They are more likely to get blocked. They used to put them on the last manhole before the main drains, but as they were so much trouble they don't do this anymore. 
I always thought internal manhole were a poor choice, and there's a good reason why they don't use them anymore.
Obviously there's a lot of people who have them without issues, but working in the trade for years I've seen enough of the mess they can create.