Help connecting 40mm anti-syphon p trap to 40mm sink waste?

[kerryj]

I've just got a 40mm anti syphon p trap to replace a normal sink u-bend (to fix gurgling sink issues). The upright part that should connect to the sink waste is 40mm, but as the sink waste is also 40mm there's no way for them to slot together.

At the other end, the p trap is large enough to slot over the 40mm pipe. I'm missing something but I'm not sure what. Can anyone help?

The existing u-bend is larger at both ends so it fits fine.

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[Madrab]

The sink end should have a ledge & rubber seal and a plastic nut that then screws onto the bottom on the threaded shank of the sink waste. Post a pic of the underside of the sink waste and the trap.

 

[kerryj]

Hi Rob - pics below. The issue is that the old one is wider at the top end so it slots up onto the existing pipe, but the new one only butts up against it because it's the same size.

 

[Madrab]

The third pic is the one that was needed. You're old one is an adjustable appliance P Trap, it's not a standard P trap, like your new one. If you took of the plastic adapter that the WM/DW drain hoses connect to, your new trap would then fit to sink waste.

The trouble is getting your original adjustable double appliance trap with an Anti Vac valve. Don't think I've ever seen any, only seen singles. If you really want to try an antivac and keep the double appliance adapter then you'll probably need to plug an anti vac valve in after the trap

You do know that when your DW or WM drains, it will always gurgle? You'll never get rid of that with that setup. An Anti Vac will only deal with a gurgle that occurs when the water empties from the sink.

 

[kerryj]

Thanks - well all problems only started when a blockage caused the WM and DW to back up to the sink. A plumber has since unblocked the drain but the DW was still backing up. Further works to attempt to resolve this has not resolved it, and has also added a prolonged gurgling noise after the sink empties, and also, but to a lesser extent, when the dishwasher drains and backs up into the sink. I thought I'd try the anti vac to see if it at least cut the noise of the sink draining. I'll look into the anti vac after the trap idea. Thanks!

Perhaps this will do the job?

 

[dilalio]

No. That's an extendable P trap... It's still designed to connect straight onto the tail of the sink waste.

I would suggest that a wet vac sucking on the WM and DW hoses for a minute or 2 would sort your current issue and then rearrange those hoses so they are up high before dropping down to the connections on the trap, would help prevent reoccurance. As well as scraping food scraps off of stuff before it goes in the DW.

 

[kerryj]

I made the assumption that the top part on the left could be removed to enable the lower part to fit to my existing 'top part'.

The gurgling is in the u-bend and is an issue with water draining from the sink more than with the DW and WM running.

The hoses are already arranged up high, but I'll query the wet vac idea with the plumber if the landlord gets him back again.

Thanks for your suggestion.

 

[kerryj]

I've had confirmation that the left top part is removable and would therefore fit onto my existing double appliance adapter, so it's now on order and I'll give it a try and report back. Thanks for your helpful responses so far.

 

[Madrab]

Yep, good one .... if it's the same maker (looks like McAlpine) then the end of the adjustable appliance adapter may be the same diam and fit the new AV P trap, once you remove the long end. Make sure the seal is the same size and nice and tight.

 

[kerryj]

Cheers Rob - although I'm a bit baffled now as it has 'magically' fixed itself today and there's no more gurgle*

I'm wondering if running the DW and WM at the same time has restored the normal balance of air in the pipes or something, but I really have no idea.

Still - if it ever re-occurs I'll get the above part re-ordered and see if it does the job. Reckon the washer will still back up into the sink so that still needs a solution but I'll leave that to the plumber.



*it was really bad - lasting more than 30 seconds every time after the sink emptied

 

[Madrab]

The drain hose from the washing machine or dish washer might be partially blocked. Run both appliances at their hottest with some bicarb and vinegar to see if it can flush things through, the other thing is a sink full of boiling water with the same stuff and pull the plug, do it a few times.