Sharing Trench Rainwater and Foul Pipework

[MortarThePoint]

I've separate rainwater and foul systems as I have a sewage treatment plant and the rainwater is going to a ditch. Most of the area where I have both foul and rainwater drainage pipes is going to get covered by a patio, so I can happily have two separate trenches a suitable distance apart. In another area, I have a run of around 5m where both are going parallel and there is no patio. Since the pipes are shallow, I want to cover them with a concrete slab path. The slabs are supposed to bear 200mm each side of the trench. A 900mm wide slab could straddle a 500mm trench and that could have two 110mm pipe runs in. One pipe will be sloping one way and the other in the opposite direction.

 

The slabs should be strong enough as I have tried jumping on one supported just at the ends and it was fine

 

Does that sound sensible? Is there anything to worry the BCO in this (e.g. Building Regs)?

 

[Russell griffiths]

The polystyrene isn’t needed. 
your over worrying. 

[Conor]

Make sure the foul is the lower of the two pipes.

 

Check the building regs, for pipes that shallow you might have to cover in concrete. Paving might not meet the needs.

[MortarThePoint]

45 minutes ago, Conor said:

Make sure the foul is the lower of the two pipes.

 

Is that a regs requirement or just sensible design? Is this in case the foul pipe leaks and cross communicates with the rainwater pipe?

 

Unfortunately, the foul will be the higher. I can stagger pipe joints so the foul would have to pass horizontally over a metre to then enter the rainwater pipe. Such a cross communication would become too unlikely to be a genuine concern then.