I am in the process of connecting my property to mains drains. I have laid 100mm diameter pipes in a trench 24 Metres long. I seem to be getting conflicting info of how to work out the correct downward slope, can anyone help?
Connecting to mains drains
- Thread starter Tonyc
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Softus said:
What are you blathering about man?
If the toilet is in position A and the sewer is in position B then they have to meet each other. The building regs are more concerned with minimum falls (1 in 40 from memory) than anything else. Do you suggest that he arrive at the sewer and find that he's gone underneath it? A must meet B with satisfactory falls to allow gravity to work - live with it.
You'll find in reality that the pipe fittings will have an offset to them that is the recommended fall. Simply work out the depth of the sewer where the connection will be made and lay the pipe at the angle of the offset. Then pipe down to it. This will give you the correct fall. That is why the bend fitting has a 92.5 angle - so the water runs downhill.
joe
SOmeone seems to think that you have to connect it up to wherever things are, and the fall doesn't matter, which is obviously not very wise.
The 1 in 40 fall is the long-revered (McGuire's rule) slope which works well. You can go as shallow as 1 in 100 and it'll work - slowly. At that slope though it's hard to guarantee there won't be any 0º bits in years' time.
1 in 40 is ABSOLUTLEY NOT a minimum, which was wrongly stated above. If the slope is too steep, the water shoots away leaving solids high and dry. That problem gets worse with increasing pipe length. You can't rely on the fittings for the slope either, 2.5º is of course about 1 in 24, and the pipe from the back of old WC's is 14º, or about 1 in 4.
To be safe, work out what you can do, working on 1 in 40. Then talk to your Building Control guys, they're always worth talking to and will advise on how you support your pipe, which may need more than average consideration depending on your soil type.
The 1 in 40 fall is the long-revered (McGuire's rule) slope which works well. You can go as shallow as 1 in 100 and it'll work - slowly. At that slope though it's hard to guarantee there won't be any 0º bits in years' time.
1 in 40 is ABSOLUTLEY NOT a minimum, which was wrongly stated above. If the slope is too steep, the water shoots away leaving solids high and dry. That problem gets worse with increasing pipe length. You can't rely on the fittings for the slope either, 2.5º is of course about 1 in 24, and the pipe from the back of old WC's is 14º, or about 1 in 4.
To be safe, work out what you can do, working on 1 in 40. Then talk to your Building Control guys, they're always worth talking to and will advise on how you support your pipe, which may need more than average consideration depending on your soil type.
joe-90 said:
I've already said what I think.
joe-90 said:
There there joe - of course you did. Don't worry, we all know that. It was the ickle wickle flow switch all along, just the like the voice in your head told you to say.
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