Foul Drainage Basics

[MortarThePoint]

For 110mm foul pipes running around the outside of the house I was expecting to dig a trench about 300mm wide, put down a bed of pea gravel and then fill to just covering the pipe with same gravel. Then topsoil over all that. Does that sound the right approach?

 

If I understand part H diagram 10, this method meets or exceeds Class B as long as the top of the pipe is at least 150mm deep. Though not sure why the vertical sides of the trench continue upwards in the diagrams. I think my shallowest pipe would have it's top at about 150mm below the surface.

 

What I'm less clear on is how far from the wall to have the pipes. All pipes are above top of concrete foundations. Further from the house feels like it leaves room for unknowns, but perhaps gets closer to somewhere the wife might stick a spade.

 

I guess same question applies to rainwater drainage too.

 

[dpmiller]

Bedding is only for supporting the pipe and the diagram reflects that. If the pipes are shallow then there's another section to read w/ concrete casing or slabs over the top for protection?

[MortarThePoint]

Oops, those 'Rigid' pipes are only clay, concrete or iron. The normal brown/orange PVC pipes are classed as flexible. That changes the normal installation to as shown below, (b). That suggests a minimum depth to the top of the pipe of 300mm which could be tricky.

 

 

[MortarThePoint]

3 hours ago, dpmiller said:

Bedding is only for supporting the pipe and the diagram reflects that. If the pipes are shallow then there's another section to read w/ concrete casing or slabs over the top for protection?

 

Depth information is only given for where vehicles may travel, like fields and roads:

 

 

And if that can't be achieved, a slab used

 

[MortarThePoint]

This is the setup I am trying to work out. Unfortunately the 450mm inspection chamber exists in the wrong direction. I'm hoping I can put a tee right next to it to solve that, since the long straight run will be roddable from the 300mm inspection chamber bottom right of diagram. I'd prefer something smoother, but can't find a product that is a 'resting bend tee' equivalent. Does this look at all sensible?

 

The existing 450mm inspection chamber has an outlet invert 600mm below the surface. 1:40 fall would necessitate 600mm - (15,000mm/40) - 2*(300mm_chamber invert steps) < 225mm.

 

Noticed a product called a shallow access 90 degree chamber which avoids the steps at the two 300mm chambers: https://www.drainagesuperstore.co.uk/product/280mm-dia-90-degree-shallow-access-chamber-base-110mm.html

 

@Nickfromwales do you get involved in the mucky pipes outside or just stay warm inside?

 

[Nickfromwales]

2 hours ago, MortarThePoint said:

This is the setup I am trying to work out. Unfortunately the 450mm inspection chamber exists in the wrong direction. I'm hoping I can put a tee right next to it to solve that, since the long straight run will be roddable from the 300mm inspection chamber bottom right of diagram. I'd prefer something smoother, but can't find a product that is a 'resting bend tee' equivalent. Does this look at all sensible?

 

The existing 450mm inspection chamber has an outlet invert 600mm below the surface. 1:40 fall would necessitate 600mm - (15,000mm/40) - 2*(300mm_chamber invert steps) < 225mm.

 

Noticed a product called a shallow access 90 degree chamber which avoids the steps at the two 300mm chambers: https://www.drainagesuperstore.co.uk/product/280mm-dia-90-degree-shallow-access-chamber-base-110mm.html

 

@Nickfromwales do you get involved in the mucky pipes outside or just stay warm inside?

 

Lol. 
 

I’m in the trenches, so to speak, at the moment.

 

I’m not shy of anything, as no job is beneath anyone, afaic. 😉