toilet waste pipe fall

11 Feb 2011
Reaction score
United Kingdom
I'm having a downstairs toilet installed. Its 4 meters from the toilet to the soil stack. what is the minimum fall need from the toilet waste pipe into the soil stack.
Thank you in anticipation
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Straight 4m pipe from behind the wc - ( bent pan connector) 50mm higher @ WC than T into soil stack ;) That really is the min. with these low water flushes. should be steeper but that`s a real world scenario using one length of pipe
Minimum required under Building Regs is 18mm/metre or total 72mm for a 4m length pipe; personally I try not to go less than 25mm/metre.

I assume you are aware that installing a new W/C is controlled building work, subject to several Building Regs. should be notified & inspected (fee involved). If is to be inspected, the BI won’t pass it if the fall is less than the minimum.

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