Plumbing connections to internal soil pipe?

[Bodgitnscarper]

Hello all.
I saw this illustration/example on a website which gives out advice on DIY.
However, I am sure I recall reading previously, that such a connection is not acceptable and will result in cross flow from the toilet into the bath/shower tray?
Shouldn't any connection only be made to a vertical section of the soil pipe?

Please advise.

Thank you.

 

[HERTS P&D]

Looks like it is leaking already!



Andy

 

[Bodgitnscarper]

So it does.
Am I right though?
Is this an acceptable method of connection?
This is being given out as advice!

 

[Hot&Cold]

I saw this illustration/example on a website which gives out advice on DIY.

This is being given out as advice!

Why not ask that site,Diy-Quack.org ?

 

[Madrab]

You would probably get backflow up into the bath yes. The person advising that will soon get a mouthful if he recommends that as a setup, someone then implements it and then gets shlt rushing up through their plughole