Rainwater pipe and soil pipe positional issues

[x60rsa]

Hello!

I'm soon to be moving my bathroom around, the toilet is currently on an exterior wall right behind where the stack is. I'm soon going to be moving the toilet to an inside wall, run the waste under the floor and it will exit as circled in the picture.

I understand I'll need to remove the current soil stack connection and fit a new one further down for the new pipe that will come from the right.

The smaller waste pipes arent an issue as they'll be going straight into the stack.

My main issue is the rain water downpipe and hopper, again ignore the other 2 pipes going into the hopper, they'll be moving.

I assume the rain water downpipe can't go into what will be the new horizontal soil waste pipe? I'm lead to believe these can only be mixed when underground?

My rainwater and soil

both go into the main sewer system due to the age of the property.

 

[Hugh Jaleak]

Regs would state that Rainwater needs to enter a Combined Sewer via a Trapped Gully, cant see the existing arrangement on the picture, but assume there is a Gully at the foot of the downpipe. However given the existing arrangement, with the Stack venting under the Eaves, if there is no noticeable odour issue in the roofspace, although not recommended, you may get away with connecting the rainwater into the stack higher up.

However, if odours are an issue in the loft, then the vent would need to be extended, using a Swan neck to clear the Eaves and vent above the Roofline. Unfortunately, it's not going to be pretty but then either dogleg the rainwater around the new Soil pipe, or take it across to the right, drop down then around the joint with the new brickwork and run back to the left, or move the underground connection to meet the foot of the new Downpipe position.