It's been many (rather nightmarish living-on-a-building-site) years with a 'temporary" drainage setup connecting to the shared sewer - we installed an IC in 2017 with an invert level of around 1.2m below external ground level. You can see one of my previous thread here where I was designing things and considering pipe routing options. We are about to have a heatpump installed by Octopus so are on a mission to get the various trenches dug and soil pipes laid/covered, in preparation for them laying the ASHP primaries in a different trench.
I need some input on which of these two options we should do :
1. Run the underground pipes directly into the deeper IC
2. Run the pipes to a secondary shallower IC, connected to the deeper IC via a backdrop shaft
Option 1
Pros : Less spoil removal outside. Less ugly due to only one inspection chamber lid outside the back door. Simpler? May go under foundations at rear easier due to greater depth.
Cons : Deeper trenches need to be dug inside the house. Shallowest 10.6m pipe to main upstairs bathroom soil stack is 1:20 - other pipes are even steeper!
Option 2
Pros : 'Correct' 1:40 fall. May be better for rodding? Shallower trenches need to be dug inside
Cons : Lots of soil needs to be shifted outside to fit the second IC, in a very limited area. More complicated backdrop shaft setup. Due to location of potential future extension back wall, to avoid it being underneath the wall, we would need to adjust the angle of the first IC 'sideways' with backdrop shaft rather than in line with the sewer towards main soil pipe, which is maybe not ideal.
Also, when we start laying the pipes, which end do we start from - the rest bend or the IC? Should the 'socket' of the subsidence rest bend be flush/above FFL, or can it be lower down, with a length of pipe extending it above floor level (and is that ideally female/socketed?)
I need some input on which of these two options we should do :
1. Run the underground pipes directly into the deeper IC
2. Run the pipes to a secondary shallower IC, connected to the deeper IC via a backdrop shaft
Option 1
Pros : Less spoil removal outside. Less ugly due to only one inspection chamber lid outside the back door. Simpler? May go under foundations at rear easier due to greater depth.
Cons : Deeper trenches need to be dug inside the house. Shallowest 10.6m pipe to main upstairs bathroom soil stack is 1:20 - other pipes are even steeper!
Option 2
Pros : 'Correct' 1:40 fall. May be better for rodding? Shallower trenches need to be dug inside
Cons : Lots of soil needs to be shifted outside to fit the second IC, in a very limited area. More complicated backdrop shaft setup. Due to location of potential future extension back wall, to avoid it being underneath the wall, we would need to adjust the angle of the first IC 'sideways' with backdrop shaft rather than in line with the sewer towards main soil pipe, which is maybe not ideal.
Also, when we start laying the pipes, which end do we start from - the rest bend or the IC? Should the 'socket' of the subsidence rest bend be flush/above FFL, or can it be lower down, with a length of pipe extending it above floor level (and is that ideally female/socketed?)
