Moving inspection chamber. Any issues?

[flanagaj]

Below is the currently designed drainage run for our house.   I am contemplating moving the IC circled in red, simply because the invert level is 860mm below the FFL and these will be a PITA with regards to the footings.   



I am wondering whether I can instead take the soil pipe out the East side of the house at a level that works and then simply run with a 45 degree branch down into either a Y on the main branch (if allowed with regs) or run into another IC further along the branch to the east side.  Yes, it will mean that there is a short section which will exceed the 1/40 slope.  That section will be used for discharging a utility room and ensuite bathroom.

The only possibly complexity is around the fact that we are on a treatment plant and I have a feeling that gasses from the tank could in theory travel up the pipe and then up the first branch.  We are planning an SVP at the head of the stack, but I am not sure this would help if we had a branch. 

[Nickfromwales]

14 minutes ago, flanagaj said:

Below is the currently designed drainage run for our house.   I am contemplating moving the IC circled in red, simply because the invert level is 860mm below the FFL and these will be a PITA with regards to the footings.   



I am wondering whether I can instead take the soil pipe out the East side of the house at a level that works and then simply run with a 45 degree branch down into either a Y on the main branch (if allowed with regs) or run into another IC further along the branch to the east side.  Yes, it will mean that there is a short section which will exceed the 1/40 slope.  That section will be used for discharging a utility room and ensuite bathroom.

The only possibly complexity is around the fact that we are on a treatment plant and I have a feeling that gasses from the tank could in theory travel up the pipe and then up the first branch.  We are planning an SVP at the head of the stack, but I am not sure this would help if we had a branch. 

You can vent an STP in the landscape or at an outbuilding.

 

Gasses would travel to the end of the run and up / out the SVP at the far end of the run. You're panicking too much about that . A better drawing showing where the pipes rise inside the house would help, stating exactly what is connected and if they rise to 1st floor or not.

 

AAV's are not require on the ground floor unless the invert is at 1300mm or more btw, and a lot of BCO's are unfamiliar with that allowance.

[flanagaj]

41 minutes ago, Nickfromwales said:

You can vent an STP in the landscape or at an outbuilding.

 

Gasses would travel to the end of the run and up / out the SVP at the far end of the run. You're panicking too much about that . A better drawing showing where the pipes rise inside the house would help, stating exactly what is connected and if they rise to 1st floor or not.

 

AAV's are not require on the ground floor unless the invert is at 1300mm or more btw, and a lot of BCO's are unfamiliar with that allowance.

If a gas travelled along a pipe which then branched and one branch went off at a steeper gradient compared to the main run, I suspect it will take the pass of least resistance.   The branched run can have an AAV, but not a SVP as I don't want anything through the roof.  

 

I assume the svp is to allow air in so as to not create a pressure differential as the water moves down the pipe, but also for gasses to escape.

 

The ensuite is on the first floor

Edited 11 hours ago by flanagaj
Clarity

[Oz07]

No problem exceeding 1.40 with pvc pipe they removed max gradient from regs

[Nickfromwales]

10 hours ago, flanagaj said:

If a gas travelled along a pipe which then branched and one branch went off at a steeper gradient compared to the main run, I suspect it will take the pass of least resistance.   The branched run can have an AAV, but not a SVP as I don't want anything through the roof.  

 

I assume the svp is to allow air in so as to not create a pressure differential as the water moves down the pipe, but also for gasses to escape.

 

The ensuite is on the first floor

An SVP is exactly what it says, Soil Vent Pipe, so needs to go to atmosphere; either through the roof, or on an external façade finishing up higher than any openings etc.

 

STP's are not part of the network, so you have no obligation to vent the main sewer gasses, as per a network connection. You just need reliable and functional.

 

Do you have somewhere to vent the STP in the landscape (can be just a short stub above ground if far enough away to not cause nuisance) or rising up behind a shed or outbuilding etc.

 

10 hours ago, flanagaj said:

If a gas travelled along a pipe which then branched and one branch went off at a steeper gradient compared to the main run, I suspect it will take the pass of least resistance.

Methane is lighter than air, so will follow that principal. Static gasses should be prevented from building up, so if there is an SVP then even a minimal convection airflow will carry this gas up and out to atmosphere, nothing to do with the path of least resistance as none of the branches going into the house will have throughput of airflow, as you say they will all be capped off with an AAV.

 

10 hours ago, flanagaj said:

The branched run can have an AAV, but not a SVP as I don't want anything through the roof.

If you want an SVP to function as a vent, then a suitable location needs to be decided.

 

Ground floor WC's do not (typically) need an AAV or a vent etc.

 

2 hours ago, Oz07 said:

No problem exceeding 1.40 with pvc pipe they removed max gradient from regs

Ok over short distances, yes.