32mm Waste Length - Siphoning Issues?

barney12 · 28 May 2006

Hi

I want to move a bathroom sink which will involve lengthening the waste.
It is currently 2m fron the stack and the move will see the waste turn a corner and run a further 1.5m. So 3.5 metres in total. I can keep the fall quite shallow without any problem.
Is this length going to cause problems with siphoning?

Thanks in advance.

Rob

doitall · 28 May 2006

yes it will give you problems. Upgrade the pipe to at least 40mm and fit an anti-syphonic bottle trat

barney12 · 29 May 2006

doitall said:
yes it will give you problems. Upgrade the pipe to at least 40mm and fit an anti-syphonic bottle trat

Hi Doitall (and all)

Ideally I want to keep to using the minamalist chrome trap on the sink.
Others have mentioned an in-line anti-syphon unit? I've Googled and tried all the ussual suspects but cant seem to find anything? Can anyone point me in the direction of what I need. Upgrading to 40mm is no problem.

Thanks

Rob

chrishutt · 29 May 2006

Upgrading the pipe run downstream of the minimalist trap should be sufficient to avoid problems, even if it's not strictly in compliance with Building Regs. If you have a pop-up waste you can adjust the degree of opening to reduce flow and hence any syphonage/gurgling noise problems.

doitall · 29 May 2006

Gentlemen

An air admitance valve is designed to let air into the pipework and prevent a plug of water sucking the seal out of the trap. In order to prevent smells entering the room they seal against a positive pressure.

They will not work unless they are fitted at the end of the run :O

posted on SF as well

Paul Barker · 29 May 2006

I wasn't aware of this, are you saying that a hepvo trap used in the basin waste would introduce smells, or do you mean strictly a full 4 inch aav as used in some soil stacks?

I've never taken an aav apart but assumed it was impervious in one direction to gases. The hepvo seems to shut so to speak, so smells shouldn't get past it, plus their info sheet shows it being used internally as an aav.

Not criticising you, just trying to learn.

doitall · 29 May 2006

The HepVo is a dry trap and not an air admittance valve, were you to fit one inline the water trap would still pull.

AAVs 32mm and above are design to suck air into the pipework and prevent the water being lost in the trap.

if it was fitted say mid section the positive pressure of the water going down the pipe would cause the valve to shut tight to prevent smells from entering the building.

AAVs are a non-return valve, they will suck air in but not let air out

chrishutt · 29 May 2006

doitall said:
The HepVo is a dry trap and not an air admittance valve

But surely the HepVo works in almost exactly the same way as an AAV and would act as an AAV even in respect to discharges from other appliances.

doitall · 29 May 2006

chrishutt said:
doitall said:

The HepVo is a dry trap and not an air admittance valve

Click to expand...

But surely the HepVo works in almost exactly the same way as an AAV and would act as an AAV even in respect to discharges from other appliances.

Yes it would if it was used as a trap or fitted on the end of the run.

Paul Barker · 29 May 2006

So are you saying use an hepvo for the trap on the furthest basin?

doitall · 29 May 2006

yes if its the end of the run.

The poster however want to fit a chrome trap, fitting an AAV or HepVo in the pipe run will not stop the trap sucking out.

ChrisR · 29 May 2006

Agreed a hepVo trap thingie in the line with the water going through it wouldn't help, but any sort of AAV near the trap it's required to protect would stop a neg pressure developing in the bulk of the pipe.

You can get 32 and 40mm ones which you can put into a tee, though I can't find a good reference online, just this:
http://database.hunterplastics.co.uk/products?group=272.
My local merchant has them! These
http://news.hunterplastics.co.uk/viewitem?newsno=58050&Archive
- the thing put onto the end of the trap - could also go in the pipe , in a void, say behind the basin..

The AAV doesn't have to go right on the trap. In a bathroom situation where a shower and basin wastes pipes join , it's the shower trap which will usualy pull out. But putting a trap with aav added, onto the basin, will protect the shower trap if the join in the wastes is close by.

barney12 · 29 May 2006

OK, so an inline AAV as close to the trap as possible is the way to go.
I can't get one behind the trap as I dont have enough depth. But, I can put one in line after the fall from the trap (The fall will be about 50cm).
I am making the assumption these AAV's can only be mounted horizontally!

Does all that sound OK?

These forums are just so great for expanding knowledge as since I starting looking at this whole shenanigans its has dawned on me why we used to occasionally get smells from the shower in this bathroom (Installed by the builder). The shower waste is 40mm and enters the stack on its own boss but I'm guessing perhaps flushing the loo or emptying the sink was enough to pull it. Mind you that run is around 3m too!

Rob

chrishutt · 29 May 2006

barney12 said:
I am making the assumption these AAV's can only be mounted horizontally!

On the contrary, AAVs must be mounted vertically. Check this.

barney12 · 29 May 2006

chrishutt said:
barney12 said:

I am making the assumption these AAV's can only be mounted horizontally!

Click to expand...

On the contrary, AAVs must be mounted vertically. Check this.

Well as your your footer says!

My not very logical brain assumed it would have to be horizontal. Why does this link them show it horizontally mounted?
http://news.hunterplastics.co.uk/viewitem?newsno=58050&Archive

??

Rob

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32mm Waste Length - Siphoning Issues?

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