Adding a soil-stack - manhole required?

[Donkmeister]

I'd like to add a soil stack to service an upstairs bathroom.

My house was built in the 1920s, and the plumbing is currently all on the ground floor. Everything except the toilet discharges into gulleys, which are also used for rainwater.

The toilet discharges straight down into the floor.

Legend has it that the sewer runs under the back gardens of the row of houses, about 10-15 feet from the back of the house. I found a manhole in an adjoining alleyway that ties up with that.

To install a soil stack, could I simply:

1) Dig out the gulley currently servicing the kitchen
2) Install stack with rest bend at bottom
3) Install an equal junction on the existing underground clay pipe
4) Feed soil stack into the "straight on" part of the junction
5) Install a new hopper/gulley for rainwater only, and feed this into the 87.5 degree part of the new equal junction

If that is acceptable I would install a boss about 2-3 feet from ground level to allow the kitchen waste to also use the soil stack. I would also have a connection at 1st floor level for toilet, bath and sink.

Knowing that this will need Building Regs approval I have tried looking at Part H but it hasn't shed much light. My concerns are:

1) Where are manholes/inspection chambers required / mandated?
2) How deep should these be?
3) If my existing sewer isn't deep enough for current regs, do I have to install a pumping chamber? A neighbour seems sure that the sewer is about 6 feet down, is that deep enough?
4) The run from house to sewer should be a straight line - are rodding points advisable / mandatory? How far apart should they be?

I'd rather avoid digging out all the way to the sewer, there is not enough room to get a digger in and I don't want to dig that far, that deep if I can help it!!!

 

[bookahandyman]

i reckon your best bet is to find the exisiting toilet piework under the ground and connect into this between the toilet and sewer run. Manholes/inspection chambers are required wherever the pipe work changes direction or is branchedinto another.
O think the depths are only relevant for new builds, as you cant change the depth of your main sewer to accommodate building regs. The last job i did the pipe was about 18 inches below ground level and the building inspector passed it. As long as the gradient is correct and its got shingle below ot and above it before back filling you should be o.k.

worth a phone call to building regs man to ask the question first, they are helpful sometimes.