Weird! Brand new bottle trap won't drain!

[RigidRaider]

This is bizarre. I have installed a small hand wash basin with a bottle trap. The trap is very close to the wall so I had to find a trap connector to make the 90 degree bend and sink it into the wall then add a kink to bring the waste back in line. The picture shows the waste pipe trim, which I optimistically included but will probably have to ditch when I come to box it all in.

Now the baffling thing is that although water flows freely out of the waste, the bottle trap is completely unobstructed and there's a healthy breeze of cool smelly air coming up the waste pipe, the trap itself fills up with water leaving the basin a couple of inches full and refuses to drain. As soon as I unscrew the bottle itself it all drains out and works fine for a few seconds until the bottle fills up again.

I can blow freely down the waste, which is not full of backed up water.

Before you ask, no, the plastic tube inside the bottle is nowhere near the bottom of the bottle.

What the heck have I done wrong? Is there some kind of airlock effect taking place with the very short horizontal pipe length?

 

[breezer]

dont know if its my eyesight but the bottle trap looks like it leans inwards, so water will not drain out becuse pipe to wate is wrong way (if you see what i mean(

 

[corgiman]

breezer is probably right, but just out of interest, how long is the run of waste pipe from the basin??

 

[RigidRaider]

Well, the trap may be a degree or two off vertical but how could that affect it? Even if it was 10 degrees out, water should still flow down under its own weight and keep spilling over the "lip" out of the bottle until it equalised inside the trap.

The distance from trap to bend is only five or six inches but from the bottom of the photo the pipe drops about 3 foot vertically under the floor then turns out and runs another couple of feet before dropping into the soil pipe for the WC you can see in the background.

Talking about it last night, we wondered if this has anything to do with the fact that this small basin has no overflow? For this reason and to avoid flooding if a child leaves the tap running we have used one of those "non-closing" wastes, which is just a cover plate like a pop-up but fixed in place. Here again, water flows freely around the cover if you remove the bottle and hold a bucket underneath.

Is there anything different you as professionals would have done in this installation?

 

[martin43]

Rigid

If I'm not mistaken it's an Ideal Standard trap, one of which I installed last year and also wouldn't drain. If you take it apart inside you'll find a clear plastic tube that goes to the bottom of the bottle effectively sealing it. This need to be cut slightly shorter, try 1 cm off it, it should then work, my one did.

Regards
Martin

 

[martin43]

Sorry, didn't read your OP properly, I'd still check it out though.

Martin

 

[ChrisR]

Are these the ones where the plastic tube can slip down?

 

[RigidRaider]

As I wrote above, the plastic tube is nowhere near the bottom of the bowl. I even cut off 10mm to be sure but that made no difference. The tube can't slip down as it has a lip at its top.

Following Breezer's suggestion I shortened the telescopic section at the top of the trap so as to force the whole arrangement upwards a little, ensuring the horizontal section is horizontal or even slightly downhill. Again it made no difference.

Experimenting with it last night I discovered that you can let the tap trickle half open and it will run happily for ever. But as soon as you open the tap fully it overwhelms the trap, which blocks and won't flow. The basin then remains full of water, not even trickling out. You have to remove the bottle to free it. There is definitely some kind of air lock effect taking place, enough to block the column of water inside the trap, up into the waste and a couple of inches above.

For the moment I have resolved it by closing the isolators to the point where neither hot nor cold nor both combined delivers enough water to produce the effect. It now runs happily but I'd still love to get to the bottom of this phenomenon!

As I wrote, the pipework is all clear and there's a draft of cool smelly air coming out of the pipe so that's clear down to the soil stack.

 

[chrishutt]

Have you got a long horizontal run at floor level? Could this be unsupported in the void between joists, and therefore prone to sagging in the middle (with the weight of water)? This could result in the phenomenon you describe.

 

[ChrisR]

I don't see that, unless the saggy bit is blocked - but there's a breeze.
What direction does the waste pipe go when it disappears in the wall?
If it went UP you'd get what you have!

Try a sink plunger. I'm not quite sure why but it might show something!
Bizarre seems a fair description

 

[RigidRaider]

Thanks for the suggestions but no, it's only about 3 feet under the floor and I made sure it had a good fall on it because it's open to the outside (don't ask!) and I didn't want it to freeze in winter.

My latest theory is that the waste is the problem. Because the little basin doesn't have an overflow and because the cloakroom will be used by kids we didn't want to risk flooding so we have used a mushroom waste, which is just an immovable cover looking like a pop-up. This is pretty close down on the basin and although water flows freely around it, I'm wondering if somehow a bubble of air is getting trapped beneath it and is prevented from passing around it by the equalising weight of the water above. I will insert a couple of brass washers on the stem to raise it and see what happens.

 

[Tinitus]

Might be worth trying a different trap, I would get an anti-vacuum extendable bottle trap not a big job to swap it over. I think it will solve your problem. The air admittance valve on the trap should allow the water to flow freely. I had a similar problem which I put down to there being no overflow on the basin

Regards Paul

 

[Nige F]

Hep V O with kitchen foil wrapped round it to look like chrome

 

[RigidRaider]

Ha ha! LOL! Thanks Nige, I'll remember that.

Problem solved!

It was the mushroom-type waste, which was fairly low in the basin. The underneath is cupped and when you filled the basin an air bubble was forming underneath the cap, exactly equalled by the weight of the water above it. I unbolted the cap, added a washer to raise it and now there's enough space for air to bubble out.

Certainly caused me a day or two of head scratching though!