waste pipes

[nskeates]

Hello,

Is there a maximum length of run into the soil stack you should have from a sink etc ? I ask this as i get a terrible smell when i use a certain sink which happens to be the longest run into the soil stack. Do not get this smell when using any other sink etc. cannot work out where the smell is coming from but it smells like waste

 

[Bahco]

When you next get the smell, take off the trap and see if it has water in or not.
If empty then you need to find out why the water is being sucked out.

 

[mogget]

Also, if the sink has an overflow, pour some bleach down it.

 

[Richard C]

Is there a maximum length of run into the soil stack you should have from a sink etc ?(

Yes 3 metres for 40mm if it's unvented & it must go downhill! but that's probably not the cause of your problem!

 

[nskeates]

it could be around the 3 metre mark and my system is unvented. what will happen if the run is over 3 metres ?

thanks for the replies.

neil

 

[Richard C]

If the branch is unvented & too long, draining a sink full of water will be slower & there is a risk of siphoning the water from trap as Bahco states! The action of the slug of water running down the pipe when you empty the sink creates a vacuum in it’s wake, air has to get in somewhere & the easiest route is through the trap (usually accompanied by gurgling noises) which means you will be left with no water seal in the trap = smells. Are the other appliances on the same pipe run or do they have separate feeds into the stack?

A little test you can try; if the smell appears after emptying a sink full of water, run the tap again lightly just to re-fill the trap; if the smell disappears, there’s your answer!

Also try moggets suggestion of bleach down the overflow; an often overlooked source of kitchen sinks smells & can get full of food particles & all manner of rotting nasties.

 

[nskeates]

thanks for the reply.

this is all happening upstairs, the problem sink is the bathroom sink which is the furthest away from the stack, joining that run i have got a 2 showers one of them i have added a non return valve. would it help adding non return valve to the sink ?

thanks
neil

 

[Richard C]

Oh so it’s a wash basin, if it’s only a 32mm waste pipe the max unvented branch length is just 1.7m! For some reason I thought we were talking kitchens & 40mm. Both Building Regs. & manufacturers design guides always recommend separate stack connections for each appliance where possible, especially if a bath, shower or loo is involved; if the branch is unvented, you’ll most likely get siphoning of one or more of the traps. If there is no choice then the waste pipe run should be sized accordingly; minimum is 40mm, but is often 50mm, witha a max. length of 4m.

By non return valve I assume you mean either an air admittance valve or anti-siphon trap!
http://www.bhl.co.uk/product.php?productid=59214

Hopefully it will cure the problem but if the pipe run is only 32mm dia. it’s poorly designed.

 

[nskeates]

it was my poor design as i done all the plumbing in the house

i will fit the anti-siphon traps to all sinks and hopes it helps otherwise i will be ripping up floor boards to re-route the waste.

thanks for the help

neil