/ Soil pipe problem

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oldie 13:03 Sat

Hoping there is a kind engineer or other knowledgeable UKCer able to offer an opinion.

We have a soil/waste plastic drainage system which involves plastic inspection chambers shared between several properties. There have been several blockages recently which appear to be due to one long, vertical soil stack delivering toilet muck into the chamber and "throwing" it into an unused and capped inlet opposite which eventually fills and then blocks the central exit channel from the chamber. This is based on a professional check of the system (including CCTV along the pipes) and we have been quoted about £4500 to have two inspection chambers replaced and the vertical stack altered, so it is no longer into a side inlet, but directly enters the central channel in the bottom of an inspection chamber.
However the properties were built in 1985 and have had no problems until recently so we feel it may be unnecessary to radically modify the system

Might a much cheaper solution be to fill the capped inlet completely (resin or concrete?) though this might simply lead to more rapid blocking if muck simply blocks the central channel earlier (at present it takes some time before there is enough buildup to start a blockage)? Perhaps we could experiment with some form of temporary block to the capped inlet.
Would it also be possible to consider slowing down the muck by introducing a roddable "kink" in the vertical soil stack near ground level, which at least should be easily reversible?

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marsbar 14:01 Sat
In reply to oldie:

Is the price high so due to the use of scaffolding?  Maybe get a few more quotes.  

Putting a kink in is an interesting idea, it might need regular cleaning, which isn't a pleasant job.  

Has anything else changed since the properties were built?  

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Lusk 14:23 Sat
In reply to oldie:

> However the properties were built in 1985 and have had no problems until recently.

This is key.
Is it your stack in question?
Have you or others started using a low water volume bog, not enough fluid to flush the drains clear properly?

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oldie 14:45 Sat
In reply to marsbar:

Thanks. The main cost would presumably be the underground work replacing two quite deep inspection chambers. I imagine only a little straightforward scaffolding or even just a tower would be necessary.

Yes, another quote (and reinvestigation) would definitely be a good idea if we considered going ahead. 

One change is that all the properties have probably had dual volume flushing replacement toilets over the years. The volume of water in the cisterns is almost certainly less and so there might be less washing effect of each flush especially when the lower volume flush is used. In addition one property had had a blocked toilet which had been unused for some time (CCTV shows its pipe to be clear now). Our old toilet was replaced after most of the blockage incidents (due to the drain engineer pushing the cleaning jet hose up the wrong pipe and smashing the bowl).  

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oldie 16:27 Sat
In reply to Lusk:

Yes, our stack is the one in question. It is a vertical pipe from our toilet (joined by waste from our bathroom sink and shower/bath) and  joined just above ground level by an almost horizontal soil pipe from our downstairs neighbour. I've mentioned the new toilet situation in my earlier reply which probably overlapped with your post....hope this was sufficiently detailed. Our toilet does throw muck into the capped inlet BUT most of the blockages occurred before our toilet was replaced with a lower volume one.

Incidentally any costs for external waste/drainage are shared between the properties so I'm not posting to try to avoid any responsibility (and wouldn't anyway)! 

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gethin_allen 17:20 Sat
In reply to oldie:

I think most of your DIY suggestions would be worth trying

If you look at soil pipes on tall buildings you'll notice intentional kinks using pairs of 135 degree bends to slow things down. 

Underground there is also a one piece large radius settling bend so that high speed  wasted doesn't damage the pipes.

You could also try to fit a deflector to the outlet in the manhole.

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oldie 18:29 Sat
In reply to gethin_allen:

Thanks. Is the deflector a standard item and do you mean blocking the capped inlet (ie opposite where the muck enters) with something to fill it, and do you have a recommendation, please?

Post edited at 18:39
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EdS 19:35 Sat
In reply to oldie:

I assume the shares I inspection chamber connects to public sewers, rather than a septic tank.

If so it's the water companies problem to solve.

Message me and I'll send you my number if you want a chat. Or weak to Environmental  Health.....they have the power to get it put right

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oldie 20:18 Sat
In reply to EdS:

Unfortunately the inspection chambers were put in during building in 1985 and are some distance from the public sewer connection.

I'll wait and see first if there are any other suggestions and will probably contact you. Thanks for the offer.

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Dax H 22:27 Sat
In reply to oldie:

Might still be worth talking to your local water authority. They had to adopt a load of private sewers and pumping stations a couple of years ago. You might get lucky. 

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flatlandrich76 23:08 Sat
In reply to oldie:

It's definitely worth checking with your water supply company first. I had a subsidence problem with my house caused by leaking drains. Once it was confirmed that the drain served both my house and my neighbors house it was classed as a public sewer and all the drain repairs were done, with no charge, by the local water company, even though the damage was entirely on my property.  

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EdS 13:34 Sun
In reply to oldie:

There was a change in legislation in 2010 ....Any private sewers or lateral drains that were build prior to October 2010 defaulted to the sewerage undertaker.

In other words they are no longer private but public sewers.

Speak to the water company first as the chamber and most of the pipe work is theirs.

If the faulty connection is a pipe that only serves one property....

a) if it outside the boundary of their land it's water company

B) if it is within the boundary of the property it serves i.e. the chamber and pipe are in the garden of house with dodgy connection......it is private. But environmental health can make the owners fix under Building Act 1990 section 59

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oldie 18:44 Sun
In reply to EdS:

Thanks, and to Dax H and flatlandrich76. It will definitely be worth checking with the water authority.

The situation might not be absolutely clear cut as the properties are a block of flats and each each being Shared Freehold ie they may be viewed as one property but it is certainly worth checking.

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malk 14:39 Mon
In reply to oldie:

re deflector- you can get flap valves that plug on end of the pipe (to prevent backflow) that would control the matter coming down?

talking of which, a mate intends using flap valves to prevent sewage backflow in a combined drainage system. what happens when backflow closes the flap during heavy rain? presumably the water in the building rainwater/soil pipes back up until the hydraulic head exceeds the backflow head- potentially causing internal flooding?

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jkarran 15:01 Mon
In reply to oldie:

Have you changed what you're flushing, sturdier bog roll, wet wipes, teenagers flushing anything nasty?

A wooden bung would be enough to test the theory about the spare port assuming you have sufficient access to measure and fit it. Make sure it can't escape and block the outlet!

jk

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