Recess distance for new toilet waste pipe

[MorganL]

We are gutting and redesigning our entire bathroom which is an 80's disaster of peach and frilly horror. Please see the photo of our current bathroom (de-tiling underway)+ current toilet layout, and my (cough) technical diagrams of what is to come

We are building a new half wall which will be a shelf on the back wall level with the window, with a shelf top that goes the full length of the room and into the window recess, one big huge shelf

The new toilet will be flush to the back of this half wall, the old boxing for pipes removed, my question is, how much room do i need to leave for the new toilet pipe arrangement (what depth of half wall). I understand too many sharp bends can be a problem and from what i understand this will be a flexible waste pipe that will go into the external waste pipe hole and connect to the back of the toilet but will have two 45 degree angles which I can soften with a bigger recess.

I want to get the basic structure of the fake wall and top / sides in place so the plumber can come out and do the toilet from start to finish, but getting him out to give me an idea of 'how much space' is needed is not easy due to his work load.

I am assuming 130mm space inside / behind the wall should be suffice? 100mm pipe, 15mm free space all around? or could I do the bare minimum 100 / 110mm

Thank you in advance for any assistance or pointers

 

[terryplumb]

Why can't the waste from WC go straight out ,and externally turn right and into the soil stack ?

 

[MorganL]

It can, I just want to make sure the 's' that the waste pipe will end up being i.e 'back of toilet turning right immediately, on a little, turn left into external pipe connector' is ok and I don't need to soften the 45 degree angles a little for good flow of waste

Note we cant drill any new walls in the house it is 120 years old, forest stone, walls 2-3 foot thick

 

[Hugh Jaleak]

Ideally need as few bends as possible, but seems you have some flexibility over the distance available, so for that reason I'd use 2 a couple of 90° bends and a straight pan connector. Bends are a slower angle compared with a pan connector, bear in mind modern, low flush toilets are notoriously useless at clearing the pan, let alone washing the contents out through a plethora of bends. Given you are seemingly reducing the length of the soil pipe internally, you may achieve slightly more of a fall over the distance between the pan outlet and the pipe at the point it goes through the wall, which can only help.

Avoid the flexible Pan Connectors, (they are awful things), use a rigid pan connector.

 

[denso13]

I am assuming 130mm space inside / behind the wall should be suffice?

I think you'll need more than that due to connecting to the existing waste and pipe collars. Better to get two bends and do a mock up first to give you the correct size.

 

[MorganL]

Ideally need as few bends as possible, but seems you have some flexibility over the distance available, so for that reason I'd use 2 a couple of 90° bends and a straight pan connector. Bends are a slower angle compared with a pan connector, bear in mind modern, low flush toilets are notoriously useless at clearing the pan, let alone washing the contents out through a plethora of bends. Given you are seemingly reducing the length of the soil pipe internally, you may achieve slightly more of a fall over the distance between the pan outlet and the pipe at the point it goes through the wall, which can only help.

Avoid the flexible Pan Connectors, (they are awful things), use a rigid pan connector.

two 90 is all I need though the first one, to be fair is ‘out the bowl and immediately right’ if that makes sense, just was making sure that was “acceptable” though I can make them slightly softer than 90. Thanks for the reassurance