waste pipe & soil stack?

15 Nov 2004
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United Kingdom
I am installing a sink in the downstairs toilet of an old flat. The toilet and the one on the floor above both feed into the same (v. old cast iron) soil stack outside the building. The easiest way I can see to plumb the sink waste into the soil pipe is to replace the present (internal horizontal) soil pipe coming directly off the toilet with one complete with 1.25" junction. This would be only 2 feet from the toilet. Is this possible and does it contravene building regs?

The toilet could not come up the sink c/o the height difference and the sink would not fill the pan up up as it discharges a low volume of water into a large pipe.

Finally, are there any problems with matching up new plastic pipes with old cast iron pipes - dimensionally that is?

Any help much appreciated, or else it's cheque book time!
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It is possible to buy a strap on boss for cast iron pipe. The regs permit you to fit a boss to the wc soil branch pipe as long as it is placed at the top surface of the pipe as common sense would dictate.

However I have never used one, they are not rated by many and they are expensive.
See if you have space to replace your pan connector for one with an inbulit connection for a waste pipe. P trap only but might solve your problem and be a lot easier space permitting. ;)

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