Waste Pipe Vent or No?

[noseall]

So we are achieving 1/60 on the foul drain line. Just shy of 17mm fall per metre when measured.

Perfect.

By the looks of it, you can be allowed to have less so that is reassuring.

Correct, as long as when its really shallow, the pipes are laid perfectly, i.e. no dips etc.

Although I've noticed some residual water does sit at the bottom of the plastic inspection chambers in the main through channel - is this normal?

Yeah it can be. Just make sure that when you concrete under the chambers (essential), try and give them a little kick at the high end.

What is annoying about these plastic inspection chambers is that whilst the main inlet is low, the rest of the branches are about 2" higher.

I feel your pain. We try and use the bigger 450mm chamber bases, for that very reason.

Having said that, we don't want th gradient to be too steep since that can be as bad as not enough (water flows faster than logs etc).

Myth.

 

[James Davis]

Nose,

My builder has bedded the chamber bases on pea gravel (beneath which is clay ground). Are you saying concrete is definitely a must?

Ps. These chambers are the big 450mm ones and the branches are all higher than the main inlet and outlet.

 

[noseall]

Nose,

My builder has bedded the chamber bases on pea gravel (beneath which is clay ground). Are you saying concrete is definitely a must?

Yes!

Ps. These chambers are the big 450mm ones and the branches are all higher than the main inlet and outlet.

The ones we use are all on the same level i.e. the through channel and the inlets.

 

[James Davis]

Yes!

The ones we use are all on the same level i.e. the through channel and the inlets.

Don't suppose you have a link? I can't find one on Google