Grounds Drainage Advice...

[StewartHitchin]

Hoping someone may be able to offer some guidance on some groundworks drainage here.

Close to completing on a new property and plan to complete a double-story side and single story rear wraparound extension. The image below shows the existing house as the red box, with the new extension in place. We were originally planning to leave the kitchen on the same side of the house, but now we would like to move this over to the green-highlighted area, with the waste drainage for the new sink and washing machine coming out of the opposite side of the house and routing around.

We are not 100% where the existing drainage to the mains waste is, but I'm fairly sure it's located around the purple line. With this being the case, we would take the waste drainage from the new kitchen location, around the house, linking into an inspection chamber which would also take the waste from the new garden room WC and the house waste too. I'm suggested to wrap around the house as the existing house has a concrete ground floor.

I've added two inspection chambers is I've heard that one should added at every 90 degree turn in the pipework. Is this correct?

Would really appreciate any guidance on whether this plan would work. Questions are:

1. Is it the route you would take?
2. Would this plan comply with the necessary regs?

Here is the proposed layout:

Here is the existing external outlets (I think these are gullies) in the house now. Sorry if that's a dim comment:

Any guidance or advice would be much appreciated.

Thanks in advance.

 

[John D v2.0]

Since you're extending the run so much just make sure you have enough available fall, so the pipes don't end up poking out of the ground

 

[StewartHitchin]

Hi John - thanks for the reply. I don't suppose you know what the regulations are in terms of fall? Having read elsewhere, is it 1:40?

With regards to the general route around the extension, do you think this is the best route?

 

[John D v2.0]

I'm not sure if there's a reg on fall as such, 1:40 is the standard but if you're accurate you could go lower. I'm not a drainage expert though so I'm sure someone will be along soon to advise.

 

[Hugh Jaleak]

You'd need to determine the depth of the existing drainage to ascertain if a sufficient fall can be obtained on the proposed new run to take the kitchen wastes. Would also be sensible to check the condition of the run to the Ground Floor WC before building over it, if any doubts as to its condition, deal with those before burying it under the new extension. What I presume is the waste for the basin in the WC should be rerouted internally without much hassle, (worst case scenario is having to change the WC.)

Drains, 1:40 is the ideal fall, but if only carrying water, as low as 1:100 fall is possible. Chamber at every change of direction, (kitchen wastes are liable to fat blockages so need to be accessible for clearing should need arise.) I dont see a better alternative for the route, provided as before, a suitable fall can be achieved. Depending on depth of pipe, some sort of projection would be required if it's getting shallow at any point. Keeping it close to the house wall and a slabbed path around the perimeter, over the pipe might also be prudent to help provide protection.

 

[StewartHitchin]

Hi Hugh,

Thanks for taking the time to reply here - much appreciated! Will definitely check the condition of the existing - good shout!

All really useful detail which we'll definitely use! Thanks.