Home  5  Books  5  Magazines  5  News  5  GreenPro  5  HelpDesk  5  Your Cart  5  Register  5  Green Living Forum
Not signed in (Sign In)

Categories



Green Building magazine

Green Building magazine

New - Autumn 2014 edition.

View the current issue.
Subscribe now.
Magazine homepage.
Browse back issues.





Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthorJTGreen
    • CommentTimeSep 5th 2011
     
    As part of an extension/refurb project (still not started - it's been a year in the planning) I want to connect our foul water to a different sewer from the existing.

    We are in an end terrace house, and our extension will go over our existing sewer connection. We are the first on the run of the existing sewer that runs along the back of the terrace (thus a private sewer up to the boundary). Another sewer runs down the side of our house to the street. As we are the first on the run at the back, what I want to do is disconnect from that sewer (cap at the boundary and backfill or whatever is appropriate) and connect to the sewer at the side of the house.

    The most direct route would be to build a new manhole with backdrop on the sewer at the side of the house - manhole to allow access for rodding, backdrop because the sewer is 1.5m down at that point and I don't want to excavate that deep under the new extension and so close to our shallow Edwardian foundations. The water company say that approval for that is very unlikely and would much prefer a junction insertion (and then we have to find a place for a rodding eye internally - nice).

    Building control have suggested a different solution, but I'm not convinced about gradients involved. Instead of going directly out to the side, the BC solution involves going directly out to the back about 7.5m under the existing house and new extension and into our garden, inspection chamber 1 and 90 degree bend, a short run of 2m into the side passageway (owned by very amenable neighbours), inspection chamber 2 and 90 degree bend, run of 2.5m into the back of an existing manhole (depth 1.4m). The water company would have less to object to, since it would be entirely private sewer coming into the back of the public sewer at a corner. It also allows work to be carried out in a less confined space and not in close proximity to very shallow foundations. It is an additional 10m of pipe, but there will be lots of digging anyway (foundations, soakaway, etc...) so perhaps a bit more won't make too much difference.

    My issue is - I don't see how this can be done without a backdrop (and hence manhole?, since I don't know that you can fit a backdrop on an inspection chamber) given that we have to get 1.4m drop in a distance of 12 metres. However, the guy at building control assured me (verbally) that they would accept a much steeper gradient for the final section (inspection chamber 2 -> manhole) as it was a) a short run, b) in the same direction of travel as the sewer and c) going into a 6 inch internal diameter pipe.

    If we *can* have a steep gradient on that section, it makes life a lot easier (plastic inspection chambers rather than a manhole and backdrop) but since I've always had drummed in that a 1:80 gradient is optimal and anything steeper than 1:40 is out of bounds, I'm a bit wary of the advice. (Even supposing that our SVP goes quite deep before the first rest bend, I would guess that the gradient on that last run would need to be 1:4 or thereabouts to get the requisite depth - this is going to block, right?)
    • CommentAuthortychwarel
    • CommentTimeSep 5th 2011
     
    I had a drop of 15 metres at an angle of 1:2.5 approved by building control for my new house here in South Wales.

    Building control approved it on the grounds that although the solids could get left behind on that gradient the next flow would push them down !

    In the end I didn't use it due to managing to negotiate an easement with the neighbour

    Also my old house had a 6 metre fall at 1:3 with no problems and the pipes are over 100 years old.
  1.  
    From the book , for intermittent or low flow rates , maguire's rule , pipe diameter / 2.5 = gradient
    100 /2.5 = 40 so 1:40
    you can make an external backdrop using a plastic inspection chamber with a bit of work . cutting in an access point nearer the top of the riser.
    i'd have thought BC will be understanding.
    • CommentAuthorCWatters
    • CommentTimeSep 6th 2011
     
    Might be worth checking the deeds to see what they say about the private sewer. You might still have to pay for it's maintenance even if you don't use it.
    • CommentAuthorJTGreen
    • CommentTimeSep 6th 2011
     
    The 'private sewer' is < 1 m of pipe, very shallow, with inspection chamber at the start of a run across the back of eight terrace houses. It becomes 'public sewer' as soon as it enters the neighbouring property. If we cap it at the boundary and take out the pipe and fill the hole as part of the foundation works then we won't have to do any maintenance on it in future, I assume, even if the deed says we must.

    The new sewer will also be private (i.e. our responsibility) until it meets the public sewer. That's fine with me if it is constructed right and with adequate inspection chambers/manholes for inspection.

    I think I will draw it up with 1:80 gradient to the first inspection chamber, 1:40 gradients from first to second inspection chamber and from second inspection chamber to manhole, and with a backdrop on inspection chamber 1 to achieve the necessary invert at that point - working backwards from the manhole. The water company are not going to be bothered about the depth at the first rest bend or the invert on inspection chamber 1, as long as the gradient going into the manhole is right from their point of view. If we can't get a backdrop on an inspection chamber, then we will have to have a backdrop manhole.
  2.  
    JTGreen wrote - The 'private sewer' is &amp;amp;amp;lt; 1 m of pipe, very shallow, with inspection chamber at the start of a run across the back of eight terrace houses. It becomes 'public sewer' as soon as it enters the neighbouring property. If we cap it at the boundary and take out the pipe and fill the hole as part of the foundation works then we won't have to do any maintenance on it in future, I assume, even if the deed says we must.

    If you remove and cap this sewer at the boundary does this mean that this sewer on the neighbours land then becomes 'private' until it meats the next boundary and the neighbour would therefore have maintenance liability where as at the moment it is a public sewer with the maintenance the responsibility of the sewage Co. .
    Any implications??
    Peter
    • CommentAuthordjh
    • CommentTimeSep 6th 2011
     
    Don't forget the law changes in October. Lateral drains (i.e. pipes carrying just your water under others' land) and private sewers (i.e. pipes carrying water from more than one house) will all be taken over by the sewerage company.

    http://www.ccwater.org.uk/server.php?show=nav.1278
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press