Anti-Syphon Trap

[hamertime]

Hello,

I have had a problem with my kitchen sink whereby at random times a stench seems to appear, it becomes so bad sometimes we actually have to leave the room. Its weird as the smell just seems to appear from nowhere then it goes after a few hours.

It is a newly built flat on the 8th floor of a high rise block and the sink has a U bend, I have spoken to a plumber on the phone and he seems to think that a Anti-Syphon Trap should resolve the problem.

The problem is I have no idea about plumbing so wondered if anyone can offer me any advice, basically the questions I need answering are below:

• What sort of Anti-Syphon Trap do I need? Can anyone show me a picture.
• How would I go about fitting it and exactly where does it attach too?

Anyway any advice would be most appreciated, so thanks a lot in advance guys.

 

[plummerman]

Am i correct in assuming the plumber you spoke to is the plumber who fitted it in the first place?? If so i'd be wondering wot is causing it rather than a retro fit item like a anti-syphon trap. How many other outlets, appliances are connected to this waste run? what size discharge pipe work has been put in, in the first place? What your describing is self- siphonage of the water seal.

Usually this will occur when a you have un-balanced pressures in the discharge. (i.e something else is running else where and causing the seal to be pulled out to allow air into the system to aid draining) or you've got something stuck in the u-bend witch is allowing water to drain through. mop strings etc. water will track over.

Place a bucket under the u-bend u should see a nut which connects to the sink, and one that connects to the waste pipe. undo these, pull the trap off and make sure there's nothing in it.

 

[hamertime]

Thanks for your reply Plummerman. The plumber I spoke to was not the guy who fitted the sink, it is a new build and I only have a washing machine connected to the waste run.

I will check to see if anything is in the U bend and check there is water present in the U bend when the smell next occurs. If there isn’t any water there do you think an anti-syphon trap would resolve this issue?

 

[kirkgas]

the anti syphon part of the trap is a bottle top sized one way vent built into the top of the trap, so you need an anti syphon "p", or "s" or "bottle" trap in 38mm if it is for a sink, either take a photo to the merchants or google McAlpine trap to identify what you want, if you live in a new build i would suggest you get the builder back, but to be honest the hassle you will have arranging access etc might not be worth the bother, a trap will be less than £10, so perhaps change that first but if that doesn't solve it you will need the builders back, in the mean time when the smell appears simply run the tap for a couple of seconds to refill the trap, don't use bleach etc, as you simply need to replenish the water.

 

[waterworks]

These traps are also known as Anti-vac traps.

 

[BigBurner]

I would fit a dry HepVO trap.

 

[joop1977]

Check if the sink has an overflow,this sometimes gets blocked and collects debris which causes a foul smell.

 

[hamertime]

Thanks a lot for your reply guys.

I've just bought a HepVO anti siphon as suggested.

Please could someone advice me as to exactly where I should fit it to? i.e. does it go in between the sink and the U bend or is it fitted after the U bend?

Any advice would be much appreciated as I really am an amateur!!

 

[BigBurner]

Thanks a lot for your reply guys.

I've just bought a HepVO anti siphon as suggested.

Please could someone advice me as to exactly where I should fit it to? i.e. does it go in between the sink and the U bend or is it fitted after the U bend?

Any advice would be much appreciated as I really am an amateur!!

No U bend needed. Screw it on the metal waste thread below the sink (the plug hole). There are two sizes so the larger 1.5" is the one you need. You may need the odd elbow, socket and pipe to connect to the existing waste pipe, depending on how the pipes are arranged.

 

[hamertime]

Great so it replaces the U bend totally, I see.

I also bought a McAlpine U-bend that has a small anti-syphon part (cap) on it.

Do you reccomend going with the HepVO or the U-bend? Which is most likely to be the most affective?

 

[BigBurner]

Great so it replaces the U bend totally, I see.

I also bought a McAlpine U-bend that has a small anti-syphon part (cap) on it.

Do you reccomend going with the HepVO or the U-bend? Which is most likely to be the most affective?

The HepVO. It is a dry trap and always seals back up. You could be away for a 3 weeks in summer and the traps dry out and come back to a stinking flat.

HepVO also act as air admittance valves, allowing air into the system preventing vacuums in the soil system. This may not be as big an advantage in a flat with a communal main soil stack, but in your case it may be, as it appears a vacuum is there sucking out the water of the trap. This may prevent problems in the basin and bath too if they are off the same branch off the main stack.

Also if the main stack backs up, the HepVo will prevent sewage getting into the sink, as it is also a non-return valve.

The best all around.

 

[hamertime]

Thanks BigBurner.

Right I think, I’ve got to the bottom on the mystery smell.

It wasn’t the coming from the waste pipe attached to the sink as I thought as the U-bend seemed to have water in it, sufficient enough to stop any stench.

But on looking under the sink I noticed there was another pipe under there attached to a different U-bend, this U-bend has a long pipe attached to it leading from the bottom of the cupboard (under sink) all the way up to just underneath of the work surface, the end of this pipe has nothing attached to it, so obviously no running water going through it. Now I can’t see where the other end of the pipe leads too as it goes behind the kitchen cupboards, presumably it is some sort of over flow pipe or something, other than that I am completly miffed.

Upon placing my hand over the open end of the pipe I can feel quite a draft coming from it so I am 95% sure this must be where the stench is coming from. So I checked the U-bend and surprise, surprise it was bone dry as it doesn’t look as if any water flows through it even though it is clearly attached to something, I dont know what theough.

So, I’ve topped up the U-bend for now and this has stopped the draft coming out of it so hopefully this is going to stop the smell, if indeed this is the source of it.

My question is does any one have any ideas what this pipe is?

It looks like a bodged plumbing job as the U-bend is clearly always going to dry out seeing as it has no running water going through it , so the smell can always waft in.

Any ideas?

 

[hamertime]

There is only one sink in my kitchen. I've just realised, could this pipe have just been added just in case I wanted to add a second sink? or maybe the builders/plumbers were originally going to add a second sink but didn't bother in the end for some reason so just left the pipe there.

 

[Rico99]

Hi there,

A piccy would be good but is this other pipe a grey flexible hose.

If so the other may have been connected to Washing manchine / dishwasher on the past.

Rico

 

[hamertime]

I currently have tenants in the flat, I was going to take a picture last night but stupidly forgot, so no picture I'm afraid.

The flat is a new build so I'm the first owner and the pipe is a bit lower down to the one connected to the sink but other than that it is exactly the same.

This is why I am thinking it may have been for a second sink or something as it really does look like thats what it could be for.

The washing machine is actually attached to the kitchen sink pipe so i do think it is for that.