New basin waste - won't drain once trap fills

[richw]

Hi all,

I've spent a few hours on this, to no avail, and it's driving me crazy. Suggestions welcome.

My in-laws bathroom basin mixer failed (broke apart). It was a Bristan mixer with a rod/lever waste and bottle trap, installed almost 20 years ago by bathroom fitters. They bought a new one, essentially the same thing, but updated to a pop-up clicker waste (slotted type, since the basin has an integral overflow). I've removed the old and fitted the new taps fine. The waste was fun because the new one is a different length to the old, so it doesn't line up with the pipework. So I swapped the unbranded bottle trap for a McAlpine adjustable one.

The problem: when running water, once the bottle trap fills up, the water no longer drains. It just sits there in the sink. If I unscrew the bottle trap enough (which presumably lets some air in?) then it will drain (and slightly leak all over my hands, of course). My overflow slot, well, one of them, is lined up with the hole cast into the basin.

What am I doing wrong? Before I touched it, the basin was draining OK. As part of my bottle-trap replacement, I cleaned out plenty of yuk, so if anything, it should be better! But as it stands, the water sits in the basin and doesn't go anywhere (I have even unscrewed the plug-top from the mechanism, and it's the same).

When searching for help on this, I see loads of advice on leaking threads, mait vs. silicone vs. 'basin mate', but that's not my problem! Anything about water not draining suggests it must be a blocked trap or drain, but I know the drain is fine, and the trap is brand new!

Cheers,
Richard.

 

[Alec_t]

If I unscrew the overflow enough

How, if the overflow is integral to the basin?

 

[terryplumb]

Pictures of the set up under the basin may be useful ,together with pics of the old and new traps.

 

[CountryFan]

Disconnect the trap from the waste pipe and discharge into a bucket or suitable receptacle

 

[richw]

How, if the overflow is integral to the basin?

Sorry, I meant the bottle trap! If I start unscrewing that, then it seems to 'breath', and the basin drains (mainly down the drain, and slightly out the side of the trap!).

 

[richw]

Pictures of the set up under the basin may be useful ,together with pics of the old and new traps.

Sorry, I didn't take a pic. It is all basically the same stuff in principle. Old waste was identical, but a touch shorter, and needed the rod mechanism. My in-laws bought a replacement tap from a merchant, and were told it is essentially the new version of the one they had (looking at them both, I'd agree).

 

[richw]

Disconnect the trap from the waste pipe and discharge into a bucket or suitable receptacle

Yes, if I just let the waste flow into a bucket, it works. But that's not ideal. . I have also poured water directly into the basin overflow and know it flows through the slot into the waste pipework.

I started doubting the trap, so I stuck it under the bath tap for a while - it isn't somehow blocked!

 

[CountryFan]

Yes, if I just let the waste flow into a bucket, it works. But that's not ideal.

Yes, not ideal but it rules the slotted waste and trap out

I started doubting the trap, so I stuck it under the bath tap for a while - it isn't somehow blocked!

Good. So I would be looking at the wastepipe and or soil stack for a blockage. If you can connect the trap onto the wastepipe only and pour water down, does it drain away, if yes, something is amiss, if no, you have a blockage.

 

[richw]

The waste pipe is fine, I assumed, because it was all fine before I started, although they said it could be slow to drain (no surprise: I cleared out loads of black gunge from the trap and where that joins to the waste pipe.

I wish I'd connected only the bottle trap (forgetting the waste and basin) and just poured water down - that's a good idea actually.

If I run some water into the basin, it works wonderfully until the trap is full, then just stops. It's making me blame the brand new McAlpine trap, but how can that be 'faulty'?! It's a blooming bit of plastic with holes in! I did wonder if, with it being an adjustable one, and I've almost got it on the shortest setting, if the collapsed pipework inside is somehow 'cutting off' the exit to the drain, so I need to take it apart and shorten it. But surely you don't need to do that? There were no instructions supplied. It's this, 32mm, A10A: https://mcalpineplumbing.com/traps/bottle-traps/adjustable-inlet-bottle-trap/

After so much faffing about, the white rubber washer/flange is rather stretched and looks like I shouldn't use it. Can I just buy a few spares of those, or would a load of silicone work on its own? Or a Basin Mate?

 

[CountryFan]

The waste pipe is fine. It was all fine before I started, although they said it could be slow to drain (no surprise: I cleared out loads of black gunge from the trap and where that joins to the waste pipe.

Who said it could be slow to drain, but you’re dismissing it?

Nothing to do with the adjustable trap.

 

[richw]

They only said 'slow', not 'holds even a tiny amount for many minutes', which is what I'm seeing. Even the tiniest little bit, just beyond the plug hole, will just sit there. It's bonkers.

 

[CountryFan]

It's bonkers.

Ime - a blockage.

 

[terryplumb]

If you connect the trap to the basin ,but not to the waste pipework,put a bucket below the trap outlet,does water run thru and basin empties ?

 

[Alec_t]

I've almost got it on the shortest setting, if the collapsed pipework inside is somehow 'cutting off' the exit to the drain, so I need to take it apart and shorten it. But surely you don't need to do that?

I'd guess you possibly do. Undo the bottom of the trap and see if the adjustable tube is blocking the trap exit.

 

[dilalio]

Where does the waste pipe drain to?
Does it go into a hopper or a stack?
Does it have its own run or does it join other wastes such as bath/shower etc?

Sounds very much like blockage or no adequate vent for the run.

You could just try an anti-vac trap but I would be also looking for gunk in the waste run. I have made a rig that allows me to connect between basin cold feed and waste so that I can push water directly down the waste pipe, be it 32, 40 or 50mm waste.

I usually try my wet vac first.