Minor public sewer diversion - How to rejoin pipes at unusual angles

[ThisOldHouse]

Hello, all. Like the great many I have found this site both reassuring and informative when approaching the unfamiliar world of underground drainage. I would be grateful for any advice on my current issue:

A 6" saltglaze public sewer runs across my back garden, at a distance of 3m from my rear wall - this is exactly where the foundations of my new extension need to go. There is a brick built inspection chamber roughly in the centre of the run, with an invert depth of roughly 1.8m. The dilly of a pickle that this presents is that the sewer pipe deviates by around 7-8 degrees towards the house, in the chamber, and then heads straight to the next chamber in my neighbour's garden, downstream.

Because there are other existing buildings in the way, my preferred solution is to use a 45 degree bend (with rodding eye access, to bring the sewer 1m closer to the house (Thames Water seemed accepting of the idea, as it would be no different to a build over as if the sewer were already only 2m from the house) and then have a plastic inspection chamber to change the direction back so it is parallel to the rear wall. There would then be a straight run under the entire width of the extension.

The problem is, as all the bends only come in 15, 45, and 90 degrees, how can I accommodate the 7-8 degrees mismatch of the two pipes once they are within touching distance - to allow me to use a second plastic IC; 450mm with reducer ring - to reconnect everything, and also accomodate the new foul from the extension.. The only solution I can come up with is to build a brick or concrete chamber (the smaller the better, so an IC, rather than a manhole), but I'm hoping there is an easier option.

All help gratefully received, as I'd like to present a good first option to Thames Water to start.

Kind regards, and Merry Christmas.

[seanandruby]

You can get 11 1/4, 22 1/2 bends. Also you can get adjustable bends from 0-30%. Pipe joints can have a slight 5% deflection. Slight correction bends are acceptable as you building inspector should allow. Best not to panic with drainage :;): Also you can read building regs part h about depths of founds with drainage because could need concrete surround.

[Tony McC]

With a salt-glaze pipe, you could look at using clayware pipes and fittings to get the angles you require. You could even convert to plasticware once you have the required angle, and then connvert back when you re-connect, if that makes things easier.

Clayware bend come in fractions of a full circle, so a quarter bend is 90°, a one-eighth bend is 45°, a one-sixteenth is 22.5° and a one-thirtysecond is 11.25°. You can cut these bends to any length you require, so, if you were to slice a 1/32 bend into pieces of one-third length and two-thirds length, you;d have pieces that would give you angles of (roughly) 4° and 8°.....and there is so much 'play' with clayware fittings within a plastic coupling that it would be incredibly simple to tweak the 2/3 length, 8° piece of bend to the 7° you require.

Although this may sound complicated, it's so much easier than you'd think!

[ThisOldHouse]

Thanks, both, for your replies - for some reason my previous searches hadn't uncovered the range of clayware fittings available. I'm much less anxious about the whole affair, now.

Sean - I will check the part H requirements first before I submit my application to Thames Water. I'll be using a private BCO, so hopefully, they'll be happy with whatever Thames Water are happy with.

[seanandruby]

Oops, i thought you were changing to plassy pipe, I C etc: