11 Apr 2014
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United Kingdom
Good day,

Our existing bathroom plumbing works as follows :

Single stack (we are top floor flat) with a vent at the top

Shower waste into low profile trap into hepvo into stack

Bath waste into trap into hepvo into stack

Toilet into bend into stack

Basin into p trap then dropa into the toilet waste pipe.

All join the stack at floor level

My question is do the bath and shower wastes need to enter a trap before they enter the hepvo traps? From what i have read it isn't necessary. The only reason i can think is that the hepvos were added at a later date and it was easier gor the plumber to add them like that than remove the existing traps.

The basin does not have a hepvo but seems to me that it would benefit from having one fitted vertically on the drop into the toilet waste. Do you agree?

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It maybe that the Hepvos were added to prevent backflow issues

Can't see any need for an additional one on the basin waste if it's a vertical connection into the pan waste
Thanks for the speedy response Newboy

I intend on keeping the hepvos but i am wondering if i shpuld do away with the standard type traps when I do my refit of the plumbing
My guess would be the HepVo valves have been put on to cure a problem, probably because the shallow traps were being "pulled" and foul smells were entering the bathroom via the soil stack.

There is no reason to fit both a standard trap and a HepVo. I would always use a HepVo instead of a shallow bath or shower trap if there's any danger of the trap being pulled or drying out.

Also they act as an Air Admittance Valve, allowing air to be drawn into the system but prevent foul smells from entering.

Sold by Hepworth (Wavin) as a problem solver, and can be very handy to know exactly what they can do.
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Think about it, golden rule of drains; air behind water, so what does two traps do?? F.cks up the whole golden rule!! There should always be an air break between two traps. Durex traps are cr.p in my view.
Yeah I guess it means its totally incapable of doing one of the things its designed for: balancing pressure. I will fit the hepvos directly to the bath and shower waste using the angle.
Remember, when installing HepVo's in a Horizontal position, make sure they are installed with the ribbed part of the body at the bottom.

Otherwise they may not operate correctly.
Anyone know a cheap supplier for these? Decided that as I have the plumbing exposed it makes sense to replace the existing ones with new. No idea how old the existing ones are

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