Trap won't fit basin outlet

[Mike-M]

I am fitting an Armitage Shanks bathroom basin and Grohe bidet. Both have outlets with lever operated plug mechanisms that screw onto the outet. The lever operated mechnisms have NF and EN274 stamped on them. They appear to be standard 32mm fittings but the outlet size is slightly too small by 1.0mm to fit a McAlpine 32mm EN274 trap. The screw thread does fit and the trap will fit onto the outlet that the NF lever fitting screws on to.

What on earth is going on here? Has anyone else had this problem and what's the solution? Fortunately I have a lathe and could probably turn out the inside oif the NF fitting but that seems like a last resort.

 

[picasso]

 

[Mike-M]

Thanks Picasso - that looks like the solution. I wish City Plumbing had offered me that when I asked them about it yesterday - All I got was a blank look!!

 

[Madrab]

Yup, had it a few times, I just file/sand the ridge/raised locating section of the trap that should fit inside the waste, until it slots in. Doesn't take much.

 

[Mike-M]

Thanks Rob.Sounds like what I imagined would be a solution. Now I've got another question. The waste fitting has two washers as in the photo. The black one obviously goes UNDER the outlet hole to seal underneath. But what is the white spongy one for? It doesn't really look luke a watertight seal. Should I use it or just use silicone under the flange?

 

[terryplumb]

The white spongy seal fits topside of the basin ,between the underside of the waste fitting and the basin. You can trash it and use silicone if you wish ( or plumbers putty). The actual shape of the "well " in some basins is very badly formed ,some very shallow and some very deep, and quite often the seal that comes with the waste fitting just don't cut the mustard !!

 

[Madrab]

As suggested, it's a compressable seal that will be drawn flat when you tighen the lower section of the waste, some basins have quite a shallow waste hole flange , others have quite an acute flange so it takes up the gap.

A basin waste can leak water at 2 places, well 3 if you include the trap to waste point ....

1st when the basin is full with the plug in and it runs past the outside edge of the waste flange, that washer stops that.

2nd is when the plug's out and the water runs down inside the waste and then passes at the internal slotted section over to the outside of the shank of the waste and then it leaks past the outside edges/under the seal and/or at the nut/thread below.

That seal you have on the waste is one of the better ones as it is fluted/wedged shaped therefore it will fill the rough gap between the basin and waste easier than a flat washer would, so you may get away with minimal silicone/mait.
I always put a fillet around the nut side of the seal at the thread before fitting the nut, just as a belts and braces to seal the thread

 

[Mike-M]

Thanks guys, that's really helpful. I can get on with finishing the fitting now.... at long last!