Replacement of Backnut on Basin Pillar Tap

[Skind56]

The plastic backnut on my bathroom basin pillar tap (cold water) broke in half after 4 years. I think it's a 'Kingston 1/2" Basin Pillar Tap' and think it's a 3/4" 19mm nut.

Can I replace with a brass backnut Plumbsure Brass Flange Threaded Backnut (Dia)19mm | DIY at B&Q - https://www.diy.com/departments/plumbsure-brass-flange-threaded-backnut-dia-19mm/136677_BQ.prd or should I get another plastic one?

Also how easy is it to replace?

Thanks for any help.
Steve

 

[Ric2013]

By all means fit a brass one (I like to use a nylon washer as well) and, so long as you are happy removing the pipework from the tap and refitting, it's no harder than it looks. If you haven't the right tools, it can be laborious to get access, but that's for you to assess.

If you are a DIYer, it will make the job significantly easier if you have a second person to stop the tap trying to turn while you tighten the nut.

 

[steadyon]

1. If its a basin tap it's much more likely to require a 1/2" BSP threaded backnut. The one you have listed is described as 19 mm - which is not a UK standard.
2. B&Q's Plumbsure Brass Female Threaded Backnut (Dia)12.7mm, Pack of 2 | DIY at B&Q - https://www.diy.com/departments/plumbsure-brass-female-threaded-backnut-dia-12-7mm-pack-of-2/136676_BQ.prd looks more likely to me.

 

[Ric2013]

Good point and agree 1/2" BSP is standard for a basin. Best bet is for the OP to take the broken backnut with her/him when buying the replacement and get the same size. And agree it would seem probable that the smaller size is the half inch BSP.

B&Q should list them as 1/2" and 3/4" (unless they genuinely are a metric size, but seems unlikely: even Italy uses British Standard Pipe sized backnuts). As B&Q hasn't a clue about plumbing, it would require a necromancer to be sure what they mean by 12.7 and 19mm or how they've measured this.

EDIT: just noticed that some of the B&Q listings state the thread size too and this would appear to confirm that the 12.7 is half inch and that the 19 is three quarter inch.

 

[Skind56]

Good point and agree 1/2" BSP is standard for a basin. Best bet is for the OP to take the broken backnut with her/him when buying the replacement and get the same size. And agree it would seem probable that the smaller size is the half inch BSP.

Thanks for replies.
Attached is photo of backnut, is it not a 3/4"? I will take broken backnut with me when getting replacement anyway.

Edit: I think the tap is 'Kingston 1/2" Basin Pillar Tap' so does the 1/2" not mean it should be 1/2" nut then? I'm confused!!

I take it that the nylon washer will also help it stay tight?

And yes getting access and having the correct tools may hinder my progress!

 

[steadyon]

1. In plumbing 1/2" or 3/4" (and others) refers to the INSIDE diameter of pipes.
2. Thread sizes of fittings refer to the size to fit such pipes.
3. Allowing for the (varying) wall thickness of the pipes, the INTERNAL diameter of a female threaded fitting to screw onto a pipe clearly has to be larger than the pipe's inside diameter.
4. Thus the "across the threads" inside diameter of a female fitting for:
4a. Half inch pipe = just under 21 mm
4b. Three quarter inch pipe = just under 26.5 mm.

 

[Ric2013]

Edit: I think the tap is 'Kingston 1/2" Basin Pillar Tap' so does the 1/2" not mean it should be 1/2" nut then? I'm confused!!

I take it that the nylon washer will also help it stay tight?

My feeling is that a half inch tap would traditionally have a half inch waterway. This would involve a nominal half inch tap rubber washer and, usually, half inch connections (which will have a half inch backnut). Of course, in these days of all sorts of new-fangled developments some of the traditional terms may not be so appropriate.

The nylon washer makes it easier to tighten without the backnut skating on the uneven ceramic and forcing the tap to move. It should take up some of the uneveness of the surface. And it just seems more correct in my mind not to be scraping a brass nut around on a ceramic surface without a washer. Seeing as they aren't expensive, I cannot see the harm in using them.