Waste Pipe Connection

[hairygrape]

There's a big pipe at the back of my upstairs toilet pan that takes the waste from the toilet into a stench pipe that runs into a manhole outside at ground level. The waste pipe comes out of the toilet pan and turns at right-angles for a distance of around 2 feet before it enters the stench pipe.

I've moved the bathroom sink over the weekend and I'm having problems routing the plastic sink outlet waste pipe into the waste pipe at the previous sink position. Would it be permissible to route the sink waste into the toilet waste pipe by drilling a 40mm hole in the top of the toilet waste pipe, pushing the sink waste pipe in a short distance and solvent-welding it into place? There is a P trap on the underside of the sink that would seal it from the undesirable smell from the stench pipe - the way I'm looking at it now is that the old sink waste pipe was going into the stench pipe anyway, so is there any difference?

Thanks

[AlBags]

A big difference.
If you connect the basin outlet there (near the WC outley) you can have siphonage problems when loo is flushed. It may suck out the P trap water seal and create a smell right away.
There used to be a reg about distance from WC outlet, but although I have them all on a disc, can't find at present.
No problem of course with siphonage on the vertical waste riser.

[Seyfitek]

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