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Replacement of Bungalow to detached house drainage issue


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Posted

Hi, 

 

I am new to this forum so apologies if this topic is already covered. I have planning permission to replace my existing 3 bed Dormer Bungalow with a 4 bed detached house with usual materials condition and a drainage condition.

 

So first attempt materials condition discharged but drainage condition refused. Reason being existing drainage to be investigated and a perc test to be carried out. 

 

we have then carried out perc test which failed due to thick/heavy clay and existing drainage investigated so Foul and Storm goes into combined manhole on my drive.

 

I attempt 2 we have submitted failed perc test results along with new design showing separate channels for foul and storm before terminating into existing combined drainage (so technically nothing new so using what is already being used for my existing house) This is yet being refused only to be told we should explore other techniques such as green roofs, swales and other above ground detention SuDS etc . 

 

There are separate systems in the road yet all recent conversions (similar to mine, bungalow to house) were allowed to use existing combined systems , it seems mine just bad luck. 

 

My frustration is them keep refusing and not talking or asking for more info, its you pay for a go and then try again.. 

 

1. I already have a house so why i can not use use existing system ?

2. Ok if i am not allowed to use existing system and want me to make a new storm connection.  Why cant they discharge the condition and i apply for the new connection ?

 

Really appreciate any advice in advance.... 

 

Posted

There is a lot of confusion here and I suspect your lack of understanding is confusing the issues.

 

So reading that you have mains drainage (i.e. you do NOT have any form of septic tank or treatment plant) and with the old house your foul and rainwater enter a combined sewer.

 

Modern practice is where possible you do not put rainwater into the sewer in heavy rain it can overload the system.  So modern practice is SUDS, Sustainable Urban Drainage.  The idea is you try and deal with your rainwater locally within your property which might be a soakaway or might be some form of tank to fill up in heavy rain and drain more slowly into the sewer.

 

Are you drawing and submitting these plans yourself?  You really need an experienced drainage designer who knows the rules in your area to draw up a design that will work within the constraints of your plot and withing your local rules.  Don't try designing this yourself. 

Posted

New builds and conversions nearly always have to deal with their rainwater on site. There are various ways of doing it using the SUDs hierarchy as you have alluded. As it turned out, Building Control are more pragmatic (and I didn’t find one that was familiar with SUDs as it happens) so they were happy with a combination of waterbutts, swale and a pond.

To actually discharge the condition needs the formal calculations etc There is a crate firm that will do them for you if you buy their expensive crates to fill your soakaway. 
Maybe look at the plans on nearby new builds and see how they managed it. 
Your structural engineer firm might have someone who does these.
What I’m getting at is it shouldn’t  hold you up if you are keen to start, but you will need the digger. 
 

Posted (edited)

Thanks for quick response @ProDave @Jilly

 

Yes - (So reading that you have mains drainage (i.e. you do NOT have any form of septic tank or treatment plant) and with the old house your foul and rainwater enter a combined sewer.)

 

However the road has separate foul and storm drainage.  (downloaded sewer maps)

 

I was thinking of doing the plans myself as Arch already failed twice and not have lot of faith , seems just printing money for himself and for the planning dept while trying to gain knowledge on my expense. ( thought i hired an expert Arch having paid premium fees) 

 

Would be happy if they talk instead of brick wall refusals... 

 

Yes i am consulting few structural engineers to see if they get me out of this situation.. 

 

So soakaway isn't possible due to heavy clay or you suggesting it might be possible maybe digging deeper and creating some sort of artificial soakaway ?  I did look at recent developments and most used existing drainage system on their property , there is one using soakway in back garden although not sure how its possible as mine failed and guy suggested whole area is heavy clay so its impossible. 

 

So what i get so far that i'll not be allowed to use existing combined system on my driveway which has been in place for years and still being used even the replacement house which is going to be same footprint so not making any addition. 

 

 

Edited by sav01

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