Drainage Issue - Help Needed!

[Richie_77]

Hello all,

I have come in search of some drainage advice, so hopefully some of you can help! (Apologies in advance for the lengthy post)

I have attached a plan of my property (right hand side) and the neighbouring property to help with the explanation of my problem…

So the RWP on the rear patio has got me scratching my head…

I noticed one day that it wasn’t draining, so I had it jetted which removed a load of gunge that had made its way down there from the rooves it is servicing. This then allowed the water to drain away, although not quite as quick as would be expected of a 4” pipe.

The guys then set about exposing the pipe in a bid to see where / if it is plumbed in. It starts off with a 90deg bend, runs horizontal for approx.. 600mm, then another 90deg back to vertical, appears to reach around 1m below patio level, and then hit a load of hardcore / rubble. Not what I was hoping to see.

The guys then opened manhole B (which is not as deep as the RWP to the rear, approx.. 650mm), ran water down the rear RWP with some tracer dye, and it eventually made its way to manhole B. The problem is it appears to be making its way into the pipe in a crack somewhere between manhole A & B. A small amount of water also eventually comes out of the pipe running from my neighbours SVP into manhole B. It also looks to be leaking from a crack underneath where my neighbours SVP pipe actually joins manhole B.

Another worrying sign is that the water level in the rear RWP drain sits a certain way up the vertical tube (I am assuming this is the same height as the lowest point of a crack in the drain pipes that it can enter) The guys vacced the water sat in the rear RWP out, and it filled back up to its previous level. (See Section A-A on sht2 attached) So now I am having visions of some sort of reservoir sitting under my property??!

The bits that confuse me are…

* I can’t see why the builder wouldn’t have connected the new RWP into the original drain, situated just to the right of Manhole A.

*There is a letter from the water board approving plans to connect into the sewer system

* This work was done by the previous owner in 2017, so I am surprised this didn’t present itself as a problem for them?

* It has been signed off by building control, but I am presuming this set up isn’t satisfactory?

* If the water is making its way through waterlogged ground etc and back into pipes through cracks, I’m surprised the dye is still so visible at Manhole B?

So there is my issue, now what is my solution!
I think there are obviously some drain pipe repairs required regardless of anything else (hopefully this can be done without excavation as they are under my utility room & walkway to side of house), then that just leaves the rainwater to deal with, which I would love to run into the sewer as it did prior to the extension (combined system) so it can be dealt with and forgotten about.

One option is to harvest the water using a butt system, although I would need a lot of capacity I think. I currently have a 230 litre butt in place collecting rain water while I figure out what to do, and its scary how quick it fills up in a heavy downpour! It is taking the water from the rear pitch of the main roof, the extension roof and also the flat roof of the utility, so I suppose it is a large area.

Another option is to try and re-route the water from the main roof, along the side of the house and join up with the front RWP. This would prove tricky (and ugly!) as there is a lot of existing pipe work on the side of the house to get past. It would be quite easy to route to the SVP but I believe this is a big no-no? This would then just leave the water from the extension roof & utility flat roof to deal with at the rear, which would be a much smaller qty and much more manageable using butts.

The other option is to try and route onto an existing drain, however the pipe would have to run from external to internal, and some utility flooring would be to come up!

Any thoughts, help, opinions or advice at all is very welcome!!

Thanks

 

[Richie_77]

Bump

 

[Hugh Jaleak]

From what I can ascertain, I suspect the Rainwater has been directed into a soakaway, (the hardcore/rubble you speak of), possibly as cheaper option than running it to the sewer. (Either this was agreed with Builder or Builder has done it off his own back and not told the Client...)
2 runs could have been laid from Manhole A, one to the bathroom, picking up the WC, Basin and Shower, a second alongside, and through the rear wall to a Gully for the rainwater.

Dye test, not quite sure what is going on there, but does seem like the water is finding it's way through to the sewerage system, either by accident or design, quite how though I am not sure. I would suggest you get a reputable Contractor in to CCTV the drains, and report on their condition before going much further, and decide on a course of action from there. Lining and patch repairs from existing manholes are an accepted solution for damaged drains, but it needs carrying out by someone competent, (see too many failed liners fitted by Cowboys who are charging 4 figure sums for the privilege.)

Interesting you note how quickly water butts would fill, so instead you hope to put this rainwater into the sewer. That in a nutshell is the issue Water Companies face with the Media screaming about dumping 'Raw Sewage' into the waterways. When it rains and all that rainwater goes into the system, it is physically impossible to collect, store and treat every last drop, hence why some has to be discharged without treatment.

 

[Richie_77]

Thanks for taking the time to reply Hugh…

Yeah it is looking more and more like some sort of soakaway, although the pipe doesnt get any more than 100mm away from the extension wall on its route down to where it ends roughly 1m below patio level, so is essentially directing all rainwater straight down to the founds?!

The other bit that is really concerning me now is that the water is standing at the bottom of the open pipe (as I have tried to detail on sheet 2 on initial post) how is that even possible considering I have not allowed any water down that pipe for a while now, how can the ground be that watertight? I have attached a couple of pics I took last night after miraculously manoeuvring an endoscope down the pipe (First 2 pics are just about where the pipe stops, second 2 pics are with the camera pushed slightly further until it reaches the bed of hardcore) It’s as if the pipe stops, there’s a small void and then a bed of rocks / stones / hardcore looking stuff. I can’t see how that is supporting the area of patio directly above it??!

Yeah strange results from the dye tests as you say, the fact that it does make its way through to Manhole B. Honestly I have images of some sort of pool under that whole section of the house, and once it reaches the level of the drain pipes it gets into cracks and drains that way. Not a pleasant thought

I take your point regarding the sewer systems being overloaded, but keep in mind the entire roof pre-extension was drained into the sewer system already, so I would just be introducing a very small additional amount from the extension roof. There was also permission granted for a new connection into the sewer system, which I am assuming is relating to this extension, as that would have been the only new addition at the time, as everything else was already directed into the sewer anyway…

I am hoping to speak to the building control officer who signed it off, and see if he has any further details on the drainage configuration. From what I can tell, it is not even close to something that should have been passed off
I’m also hoping to speak with the water board to see if they can shed any light on what exactly the new connection proposal was, or if it was even done at all.
It’s definitely a head scratcher!
If any of the above is a bad idea, or you have any further suggestions / advice, please don’t hesitate to let me know!

Thank you