1/2" Blanking Cap Vs 15mm Blanking Cap - Difference ?

[WhatNext]

Hi there

My apologies if this question is a bit daft !

I need to blank off the male threaded section of a tap connection which I believe is 1/2" BSP - please see the attached picture.

I have found a 1/2" Female Blanking Cap which I think is a BSP thread which I believe will do the job.

However when I went to purchase the blanking cap I found that there was also a 15mm version ?

I was wondering what the difference was and why both exist ?

Many thanks in advance.

 

[Mottie]

• THIS IS TO SEAL A 15MM COMPRESSION FITTING. Thread is 1/2 inch BSP thread
• Important note- These blanking caps for 15mm fittings have a 1/2 inch BSP thread which actually measures 3/4 inch when measured with a measuring tape or caliper due to how BSP fittings are measured. Normally used to seal 15mm compression plumbing fittings which have a 1/2 inch BSP thread . Very flexible product that can be used in cold, hot, compressed gas and air applications and central heating systems.
• Most plumbing products are measured using BSP thread dimensions which measure 1/4 inches larger than that stated, therefore this 1/2 Inch BSP thread measures approximately 3/4 inches in diameter

 

[WhatNext]

Hi Mottie many thanks So the 1/2" Female Blanking Cap that I have is the right one for the 1/2" x 15mm Tap Connector that I have. However if I wanted to blank off say a 15mm compression fitting then I would need a 15mm blanking cap ?

 

[fixitflav]

However if I wanted to blank off say a 15mm compression fitting then I would need a 15mm blanking cap ?

I assume a blanking cap for that is a short length of 15mm pipe, capped at one end. If you can buy that, fine, if not, easy to solder a 15mm male blank to a pipe length.

 

[CACKATALLTRADES]

Hi Mottie many thanks So the 1/2" Female Blanking Cap that I have is the right one for the 1/2" x 15mm Tap Connector that I have. However if I wanted to blank off say a 15mm compression fitting then I would need a 15mm blanking cap ?

The female blanking cap you have doesn't care about the size of the pipe, only the size/pitch of the male thread.
A compression coupling for a 15mm pipe is almost certain to be ½ inch threads so your ½ inch cap should work but you will need to put a rubber washer or disc inside the cap if it didn't come with one. It doesn't matter whether there's a hole through the centre of the rubber so long as it makes good contact with the lips of the fitting.
If you want to blank off 15mm pipe with no pre-existing fitting, you can get a compression stop end.

 

[Jackrae]

• THIS IS TO SEAL A 15MM COMPRESSION FITTING. Thread is 1/2 inch BSP thread
• Important note- These blanking caps for 15mm fittings have a 1/2 inch BSP thread which actually measures 3/4 inch when measured with a measuring tape or caliper due to how BSP fittings are measured. Normally used to seal 15mm compression plumbing fittings which have a 1/2 inch BSP thread . Very flexible product that can be used in cold, hot, compressed gas and air applications and central heating systems.
• Most plumbing products are measured using BSP thread dimensions which measure 1/4 inches larger than that stated, therefore this 1/2 Inch BSP thread measures approximately 3/4 inches in diameter

Just to clarify, here are the 'official' figures for 1/2"BSP
Major diameter 20.955 mm / 0.825" Threads per inch 14

 

[Madrab]

Wouldn't use a female blanking cap with a rubber seal on a compression fitting, the end will bite into the rubber seal and invariably it will leak. Only use them on 1/2" flat faced ends.

I would always use a compression blank on a compression fitting.

 

[tyro]

Hi Rob,
I have just read this thread as I struggled to blank something off at am ancient compression fitting. I couldn't get it to work with a blanking cap, not sure if the inside lip of the compression fitting wasn't clean enough but also it didn't have much thread compared to my nut and I think it may have bottomed out thread before getting much force on the cap.
I had to stop for lunch so put a female blanking cap with rubber seal on and although I get your point about the sharp edge it seems to have worked. You mention invariable leaks but is that something that will inevitably happen later or since I've got lucky when I put it on does that mean it will be ok?
Also the old compression fitting didn't have hex nuts, just ridges running parallel to the pipe. Is there a matching plumber's tool for those? I couldn't see anything on screwfix.
Thanks,
Simon

 

[Madrab]

Not ideal resurrecting and old thread but ......

Went to a clients house just last week, water pi$hing out of the flexi female end above the cold ISO to the basin tap. Unfortunately the client didn't know all they had to do was turn the ISO off to stop the flood. Anyway, isolated the water and pulled the female flexi end off the valve, the rubber seal had split all the way around in a perfect circle and the water ended up leaking past the seal. The previous chap had installed the basin about a year previously and tightened the female flexi (and it's washer) straight down onto the end of the compression ISO.

So, it had taken that year for the sharp end of the ISO to work it's way through the washer and it has ended up with the cabinet as well as the laminate flooring. That was a working supply of course and the on and off action was probably what caused it to slowly chew it's way through but TBH I don't think I would take the chance