fred wrote:

I was trying to work out the objection for the strap on but I suppose it the
lack of a sweep meaning that passing fluids could go back up the branch.
Sounds pretty remote to me. I thought of that when doing mine (in an
enclosed location) and placed a step drop of about 150mm in the branch
just before the joint to the stack.

In England that is a building regs requirement, see page 8 onward:

http://www.planningportal.gov.uk/upl...F_ADH_2002.pdf


--
Cheers,

John.

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