P-Trap problems

[odgeuk]

Hi all.

So my dear old Mum told me she’s always had a leak under her kitchen sink, while I was there to replace the taps. I could see it was damp but cracked on with the taps, dreading that it might be a leak from the compression fittings that I was securing my new tap tails to. Well, long story short, I realised it was actually a slow leak from the sink waste. I unscrewed it, to find a total travesty.

That pipe has just been cut and doesn’t butt up to the waste trap at all, just goes up inside it!

Anyway, I figured one of these would do:

(In the foreground is the original butchered Mcalpine part. In the plastic wrapper is the proposed B&Q replacement).

However as you can see, the angle of the bend is tighter on the old part, so things don’t line up….

Both are 40mm

What am I missing?? What do I need here..

 

[MeldrewsMate]

There is a joint halfway along the new trap, loosen this and you'll be able to rotate the coupling and line up the outlet to your existing pipe, then retighten it.
Alternatively modify the downstream pipe by 1/4" or so to allow for the extra length of the new trap.

 

[MeldrewsMate]

Also it looks like the old trap was adjustable for height. You could always cut the (correct) flange off the B&Q part and slide it into the old trap's compression fitting....or exchange it at B&Q for an adjustable P trap.

 

[odgeuk]

There is a joint halfway along the new trap, loosen this and you'll be able to rotate the coupling and line up the outlet to your existing pipe, then retighten it.
Alternatively modify the downstream pipe by 1/4" or so to allow for the extra length of the new trap.

I just couldn’t get the B&Q one to line up, even with rotation. The width of the new one is just too much larger.

 

[MeldrewsMate]

Plan B is therefore to read post number 3 of this thread.

 

[Madrab]

The old trap is a McAlpine adjustable height trap with the top waste connection and nut cut off it for some reason and a 40mm nut and sealing washer added

You need to get the same again (screwfix) but this time don't cut the top nut off but if needed take the inner adjustable trap tube out and cut from the bottom. Check it is actually a 40mm nut the sinks basket waste takes too.

 

[odgeuk]

Plan B is therefore to read post number 3 of this thread.

Cheers, that makes sense. I’ve left it for now but will see if I can make that work when I get back to it. One problem I think I’m might have is that I couldn’t unscrew the highest nut / compression fitting on the old trap, it felt glued. But I might just need to try more force..

 

[odgeuk]

The old trap is a McAlpine adjustable height trap with the top waste connection and nut cut off it for some reason and a 40mm nut and sealing washer added

View attachment 328158

You need to get the same again but this time don't cut the top nut off but if needed take the inner waste tube out and cut from the bottom. Check it is actually a 40mm nut the sinks basket waste takes too.

Yes, this looks spot on. Many thanks. The waste trap in the sink is defo 40mm. I don’t quite follow where I’m cutting though (if need be)?

 

[Madrab]

If you loosen the 2nd nut down on the left, the adjustable height tube with the nut that connects onto the sink waste will pull right out. If you offer up that trap connected to the outflow waste pipe and that upper piece of pipe to the sink waste connection is still too high, it will only slide down into the trap so far then it bottoms out. if it needs to be a little lower then take the tube right out of the trap and cut the bottom of the pipe so it can slide right down to the bottom of that section of the trap and give you more space.

 

[odgeuk]

If you loosen the 2nd nut down on the left, the top adjustable height tube will pull right out, so if you offer up that trap and it needs the top waste connection to be a little lower then take the tube right out and cut the bottom of it so it slide right down into the trap.

Perfect. I understand. This is great thanks. I’ll order the Mcalpine replacement.

One thing I don’t understand. Why is a height adjustable P-Trap narrower / shorter in width than a standard P-trap?

 

[Madrab]

not sure what you mean about shorter/narrower? they are all standard diameter, the actual trap shape may be a little different, maker dependent. The Mcalpine part is far superior than the Floplast

 

[odgeuk]

Just this dimension here in blue. Being shorter in this dimension means that it’s not easy to grab an off-the-shelf replacement from another manufacturer (e.g my B&Q P-trap). Always assumed these things were kinda standardised!

 

[Madrab]

Nope, they can all be slightly different but even then you should be able to adjust the trap angle to make up for that difference by adjusting the angle of the right hand section that fits into the outflow in relation to the rest of the trap.

The trick with these is just loosen every nut on the trap a little and line/connect everything up, tighten the nut on the sink waste connection and the outflow connection, then twist the trap body to get it to fit evenly/straight and then tighten it all back up.

The one issue sometimes is that the flange of the trap doesn't fit into the throat of the sink waste properly, they aren't made all the same size either, if that happens just trim the outside face of the the little upstand section where the rubber seal sits (top left of the picture) with a sharp knife/stanley or file until it fits in