Maximum drainage pipe fall for rainwater

[Peter500]

I'm installing ACO channel drains for a new patio. There's a rainwater drainage pipe nearby, but it's about 800-1000mm deep. To connect directly, I would need a really steep fall (much more than 1:40). Is this ok for rainwater, or is there another way to connect it? I'm worried about blockages due to the fall being too steep.

The ACO drain is running parallel to the drainage pipe and probably about 1-2m away. I'm have a small ACO sump unit, so an outlet will come out at 90 degrees. I'm planning to turn the sump unit outlet at an angle so that I don't need such sharp bends.

 

[StephenStephen]

I guess you mean: much more than 1:40 ?
Personally I can't understand why a steep fall would increase the chance of blockage - generally a stream might block but a waterfall won't.

 

[phatboy]

Drop shaft is the way to go

 

[Peter500]

I guess you mean: much more than 1:40 ?
Personally I can't understand why a steep fall would increase the chance of blockage - generally a stream might block but a waterfall won't.

Yes, I've updated my original post

I believe solids can get left behind if the water flows too quick due to a fall that is too steep.

 

[Peter500]

Drop shaft is the way to go

So an inspection chamber?

I generally don't like having more inspection chambers, but if I put it in the right place then I could have my other drain pipe feed into it and they will then be roddable.

 

[Peter500]

I've noticed that the plastic inspection chambers don't have holes near the top. Can I use one of those and drill/cut a hole for drainage pipe entries? Or would it need to be brick built?

 

[phatboy]

For purely rainwater, I'd skip the chamber and just make sure there was a leaf guard in the end of the ACO.

If you use a chamber, yes you cut your own 110mm holes in a plastic riser at the height you need, then fit a blank in the pipe. The drainage would go into the chamber base via the backdrop, not just pour in from the top hole which would be noisy and a bit rubbish.

 

[noseall]

I'm worried about blockages due to the fall being too steep.

Never heard that one before.

 

[Peter500]

I've realised that the over-priced ACO sump unit is probably useless. The cut outs at the bottom of the channel drains are around 68mm, which means I probably wouldn't be able to get my hand or tools into the sump, which is 110mm.

What would be the best option for this pipe? Do a steep angle straight from the drain to the main drainage pipe or drop straight down from the channel drain and then have a 90 degree bend and a 1:40 fall?

 

[denso13]

I believe solids can get left behind if the water flows too quick due to a fall that is too steep.

Just a myth but definitely no issues for rainwater.

 

[Dereekoo]

Never heard that one before.

It relates more to foul drainage with turds etc being left behind because the water flows to fast past them instead of carrying them along

 

[noseall]

It relates more to foul drainage with turds etc being left behind because the water flows to fast past them instead of carrying them along

Myth. I’ve never seen it happen.