Adding a toilet downstream of another

[JimmyJohnJoJr]

Hello, I'm reworking our ensuite which is next door to the main bathroom.

I want to connect the new toilet into the existing soil pipe which runs directly under it.

See the picture below for the layout.

Can I simply put a strap boss on to the existing soil pipe or is there anything I should be aware of? (I've heard siphoning, do I need to counter this?)

Thanks in advance, I really appreciate any guidance

 

[JimmyJohnJoJr]

Doing some more reading on this which prompts more questions:

1. Do I need an AAV and where should it go?

2. I don't have space to put a swept connection in on the new toilet, it'll probably have to be a 90° connection into the horizontal soil pipe. Do I need to put some sort of backflow preventer to prevent stuff from the new loo sitting in the pipe between the two loos?

Thanks again

 

[MagicDoughnut]

If you have a good fall you will not have stuff sitting in the pipe. Too much of a fall and the water will flow too fast leaving solids behind.

Yes, there is a risk of the existing toilet flush to suck out the water out of the old toilets trap. You don't need an AAV as I will assume your main stack is already vented. You can fit a vented pan connector on the existing toilet to counter that possibility.

 

[JimmyJohnJoJr]

Cheers MagicDoughnut, that's helpful. I'll make the space for a swept connection. I've ordered a '92° triple socket branch'

I'll have a look at putting a vented pan connector on the first loo, hadn't heard of one of those.

I'll be on again soon enough with more questions. Cheers!