More soil stacks - replace with hepvo?

[Tom Pickles]

Merry Christmas!

Following on from my previous queries about our badly designed and executed soil ventilation stack situation....

I'm liking the idea of capping off both of our soil stacks with access caps and using Hepvo waste traps on all of the sinks, baths, shower etc. This will prevent me putting in what will likely be unreliable air admittance valves and will also stop any warm damp air from entering the loft and causing damp, dry rot etc situations from becoming a problem in the future.

It's going to be a PITA to do, but I'd rather do the job done right first time.

Would I have to change all of the following p-traps with hepvo's or just some?:

Soil stack #1 services:

1x sink in utility 1x sink in kitchen 1x basin in en-suite 1x shower in en-suite (plus WC in en-suite)

Soil stack #2 services:

1x basin in d/s toilet 1x basin in bathroom 1x bath (plus WC in d/s toilet and bathroom)

Many thanks.

[Tim Watts]

Essentially one on each sub-line.

eg if you have washing-machine : dishwasher : sink

on the same bit of 50/40mm then on HepVO should do.

But you'd want another on the bathroom basin -especially if that connects into a different stack or a stack adjacent to a loo (loos cause big local suction effects).

You'll know if you don't have enough if any traps end up gurgling when flushing loos - especially when flushing lots of bog paper as this forms a fairly effective piston in the pipe.

So if you're not sure, leave the pipes exposed where applicable for a month and see how it pans out in case you need an extra one, but if you stick one on each logical sub branch, I don;t think you'll have any trouble.

I put one 110mm AAV behind the loo where the basin joints in nd that does "fire" occasionally.

I didn't bother with any AAVs on the kitchen or bath branch and both, although long branches in 50mm, drop into their personal grey-only 110mm pipe that goes into a pit that also sports the open to air main vent.

What I'm saying there is think about the causes of suction and where they are and what they impact in the locality and consider HepVOs there first.

The Building Regs Approved Doc on drainage will also offer some general guidance - AAVs and HepVOs perform exactly the same function, so where the Docs say AAV, consider a HepVO.

Cheers

Tim

[Mathew Newton]

Be aware that using the Hepvo's essentially as air admittance valves may result in them producing an unacceptable rasping sound as they operate.

Mathew

[Tim Watts]

I can't answer for HepVOs - but:

some unknown AAV in 110mm format I knew at work made a hell of a "parp" when it operated.

My Floplast 110 AAV makes a discrete "blurp" and a 50mm Floplast AAV I also have in the spares box seems virtually silent - though I've only mouth operated it.

[Doctor Drivel]

No. The cross section of the HepVo's must be the same as the 110mm pipe. I have found that they are fine with about 2/3 of the cross section.

Using HepVos means the pipes in the loft can be capped off and covered with insulation preventing heat loss into the loft and stopping rot up there. A win, win. Also the 110mm pipe can be removed from various sections when decorating, giving more space and cleaner lines with no boxing.

HepVos, are dry not drying out in summer when on hols, coming back to a stinking house.