Combined rain/sewage pipe hindering fresh air

[ameliacm]

Hi there,
Apologies for the mammoth post but my neighbours and I really need some advice...

I recently purchased a flat that was built in 2016. The apartment is still under the NHBC 10yr warranty. Since moving in, I discovered that the rainwater pipe that runs through my winter garden balcony at one end of the property is connected to a combined water/sewage system with the terrace houses across the road. The smell is awful, like rotten eggs, and unfortunately, the winter garden balcony is the only way to get 'fresh' air into the property at that end of the flat - so this is a real issue.

The neighbours in the two flats below mine who have the same layout have also experienced this problem - they started a conversation with the building management company and the original builders in 2017. After much back and forth, we managed to get the builders to come, clean the pipe and add a non-return valve at the bottom of the pipe, which solved the issue for a short time, but now the smell is back with a vengeance. Another neighbour in the block next door, presumably with a different connection to the sewage system, has just also reported the smell entering his property.

This other neighbour today has had a plumber come and investigate - he said "yes the drains are connected to the sewer, not ideal but it is what it is. The problem is that these drains should all have water traps (like a toilet system) with standing water to prevent air from coming up from the sewer, and these traps would need regular waterflow to ensure they stay full of water.

In my case, as I'm on the top floor, I have two drains on my balcony, one that swan necks from the main stack, and one that comes directly up from the main stack. I'd previously put a non return valve on top of the swan necked one and didn't realise i had another vertical drain. Today as we took up the decking we found the vertical one and it was literally blowing sewer air straight up! I've now blocked up that vertical drain, and have the non-return valve on the other, so things are much better (though still not perfect).

Weirdly there's a different drain configuration on each floor and the third floor doesn't even have a drain, so the whole set up is shoddy as hell.

Apparently the ideal fix would be to have traps installed under each drain (which is a fair bit of work, and would be visible on balconies. Failing that as a short term fix, blocking the drains/using non return valves does help."

Files attached:
Pipe location - shows where the pipe and the additional drain are located under my balcony decking.
Floor plan - shows the location of the pipe in the property - with a green star for the pipe



My question is:

1. Is this diagnosis correct - do we need to push the original builders to install the water trap systems in each balcony?ll.

We're getting to a point where we might need legal advice, as neither the builder nor the management company are willing to help.

Any advice would be much appreciated.

Thank you!!

 

[fowlerboi]

Surely the best option is at the bottom of the downpipe they dig in a trapped gully which does all the flats in one hit?

 

[ameliacm]

Thanks @fowlerboi - that sounds like something that should absolutely be included in the drain... but definitely doesn't exist. Thanks for the picture I used this in a response to the builders.
The rainwater pipes actually connect to the pipes in the Sainsbury's local below our flats, so that's where the builders have added a non-return valve but it hasn't done anything. The other flat owners and myself have taken it upon ourselves to add our own waterless drain seals at the end of our pipes which seems to work about 95% of the time to keep the smell at bay.

The builders have recently been to Sainsburys to investigate:
"... we were able to lift a few ceiling tiles to review the trap that has been previously installed and the pipework above the ceiling line under your properties. We have identified an issue further along in the line that we need to talk to Sainsburys about as there is a connection from a sink into the Rain water pipe I have requested a chat with the manager of Sainsburys"

Is it weird that residential flats connect to the same drainage system as a commercial business? This seems really weird...

 

[ShaunCorbs]

I would say they’ve combined it as it was easier for them to do have you asked the water board is this allowed some do some don’t might give you a bit of welly to give to the builders

 

[ameliacm]

I would say they’ve combined it as it was easier for them to do have you asked the water board is this allowed some do some don’t might give you a bit of welly to give to the builders

Ohhh this is a great idea, I haven't contacted the water board but I will.

I'm also considering getting a drainage survey done. Kicking myself I didn't do this when I bought the property but it was just another cost... is this a worthwhile exercise - will it give me more ammo for the builders?

 

[ShaunCorbs]

It’s one of them might not find anything other than untrapped gully for the rainwater but might find something else it’s one of them maybe all the tenants go in for it ?

 

[Chuck]

Who owns the freehold of the property? Remedying these problems would normally be their problem.

My first step would be to contact the water board to establish where their responsibility ends and the freeholder's begins and to get some free advice about what needs to be done to bring the connection to the sewer up to standard. (It's illegal to make/modify sewer connections without their approval in any case.)

Drains for blocks of flats can be quite tricky. I wouldn't let the builder who got it wrong in the first place try and bodge a fix. Get a professional to specify the remedial work needed. If you're not sure who get, try asking whoever did the survey when you bought your flat to recommend a firm.

 

[Deleted member 120897]

In the photo, where the downspout comes down to the grating, is that not trapped there? Also see attached - a screenshot from building regulations document H.

 

[Ric2013]

Hard to say without knowing the details but in general a drain must have an open vent (no traps or valves) somewhere. This should be at least 3' above a window or 10' horizontally from it. And, logically, not on the balcony either. If no vent, pressure can build up.

The adding of valves with no dedicated vent in place may be why you now have so much foul air coming up to you : it has fewer other places to go.

 

[ameliacm]

Who owns the freehold of the property? Remedying these problems would normally be their problem.

My first step would be to contact the water board to establish where their responsibility ends and the freeholder's begins and to get some free advice about what needs to be done to bring the connection to the sewer up to standard. (It's illegal to make/modify sewer connections without their approval in any case.)

Drains for blocks of flats can be quite tricky. I wouldn't let the builder who got it wrong in the first place try and bodge a fix. Get a professional to specify the remedial work needed. If you're not sure who get, try asking whoever did the survey when you bought your flat to recommend a firm.

Unfortunately, the freeholder and the original builder are the same company. The email chain about this problem has been going since 2017, wild! And half that time was the management company and the builder blaming one another - only once we threatened legal action did they spring into the investigation.

Thames water came out last year to try and view the situation but said it's a private drain so they couldn't gain access.

Would a drain surveyor be able to get access and map out my section of the drainage system from the pipe on my balcony. It's sounding more and more like this might be the best way forward, to get some independent advice.

I asked my original surveyor and he's recommended a couple of drain survey companies. Should I ask for a CCTV drain survey?

 

[ameliacm]

In the photo, where the downspout comes down to the grating, is that not trapped there? Also see attached - a screenshot from building regulations document H.

Hi Chris, No it's not trapped - I have last week put a green drain 4" trap seal over that and the other other pipe (there are two) in the balcony so water can go down but the smell can't go up. It works 90% of the time.

Thanks for the reference, this will be really useful once we diagnose the problem.

 

[ameliacm]

* Update * After loads of investigation by the builders - it's been discovered that Sainsbury's (which our properties are built on top of) actually added some pipework onto the residential rainwater pipes. This is what we have been told by our builder/freeholder:

"Sainsburys FM are removing their pipework completely From the RWP and rerouting to an SVP further back in the shop.

(they will then clean the pipework) The clean is to remove any possible debris left and upon completion of this and the clean from above we are expecting the issue to stop.

We will keep the pressure on the facilities company going."

Do we as homeowners, have a case against Sainsbury's?

 

[snowhead]

Do we as homeowners, have a case against Sainsbury's?

No.
Sainsburys are a Leaseholder just as you are.
Any claim would be against the Freeholder and probably via their Property Management co.

If Sainsburys are deemed to be at fault then the Freeholder / Management company would have a claim against them.

You and any other affected Leasholders have possibly got a claim against the Freeholder's Property Management company / Builder - Freeholder for mismanagement of the issue, good luck getting anywhere with that though.

And the issue of incorrect / lack of trapping of the balcony drain will still need sorting out including removing of any non return valves that are blocking venting.

Is it weird that residential flats connect to the same drainage system as a commercial business? This seems really weird...

It's not weird, it's quite common for drains from flats above / adjacent to commercial properties to pass through and or connect with theirs.

 

[ameliacm]

No.
Sainsburys are a Leaseholder just as you are.
Any claim would be against the Freeholder and probably via their Property Management co.

If Sainsburys are deemed to be at fault then the Freeholder / Management company would have a claim against them.

You and any other affected Leasholders have possibly got a claim against the Freeholder's Property Management company / Builder - Freeholder for mismanagement of the issue, good luck getting anywhere with that though.

And the issue of incorrect / lack of trapping of the balcony drain will still need sorting out including removing of any non return valves that are blocking venting.



It's not weird, it's quite common for drains from flats above / adjacent to commercial properties to pass through and or connect with theirs.

Thanks for the advice... makes total sense. Will continue to pursue the resolution of the trapless rainwater pipes also then!