Remove waste gully and create enclosed pipework

[wingit]

My 1930's house at the rear garden, the open drain gully has cracked all around and now leaks, and I'm about to renovate the patio area, most likely grass and some large porcelain slabs.

The waste on the right from the bathroom shower upstairs is an open type down to the gully, two pipes out from the kitchen.

The pvc pipe comes out from under the kitchen from the cloakroom and joins the open gully pipe at a Y just before the manhole.

The upstairs toilets have waste through the pipe on the left and have their own connection to the manhole outlet.

The manhole shows the pipe exiting to the next door neighbour's side downhill.

I hope to replace the pipes seen on the right with an enclosed system, the pipe from the the shower waste down to connect directly into pipe currently in the gully. Connecting the two pipes from the kitchen, kitchen sink, dishwasher etc. from one pipe, washing machine from the other pipe, into the new downpipe.

There are two small outlets from the unvented cylinder, one small overflow I think and a second pipe that runs under the door into the gully, I'm not sure how that could be connected into a new enclosed waste.

Is my enclosed waste plan suitable?
How could the boiler pipes be connected?
Does this need permission from Thames water or the council?

Any advice gratefully received.

 

[Hugh Jaleak]

What I would do, as follows. Soil Stack, you've already got a Plastic Branch from the upstairs WC, adapted to the Cast iron section before its adapted back to plastic. Replace the Cast with Plastic, and you can connect the two wastes from Upstairs into that, and remove the current pipework run from the left side, along with the Hopper and Downpipe. Tidies that up.

Gully, I'd look at removing the existing and replacing with a new Plastic Bottle Gully, before reconfiguring the sink waste pipes into that. They can be made to discharge below the Grid, meaning you can ditch the Gully surround and site the new Gully level with proposed finished floor level. Much neater and quite inconspicuous.

Cylinder Discharge, really needs left exposed so you can see if it's discharging as that indicates a Fault situation that needs attention. I would suggest some kind of cage over the end though to prevent any injuries should it emit boiling water and someone gets too close.

As the intended work is on your Private Drains, Thames wont need to know, (unless you mess about with the Manhole), and given you are only altering existing above ground pipework in the main, and replacing a Gully like for like, then I wouldn't worry too much about Building Control in this instance.,