1/2" Black Alkathene pipe fittings

[aidan.f]

local allotment have had brass taps and  fittings stolen from the stand-pipes. 
I do know we have a 1/2" pipe OD 21.5mm
https://www.stevensonplumbing.co.uk/black-alkathene-pipe-fittings.html

The name of the pipe does not match it's actual dimensions... 

Looking for replacements Philmac advertise their fittings as universal
Descriptions  though are inscrutable and Philmac catalogue is no help

hilmac 3G Metric Wall Plate Elbow (Plastic) - Black, 25mm/¾" x ¾" BSP part 9032

https://plasticsuppliesdirect.co.uk/philmac-3g-metric-wall-plate-elbow-plastic-black-25mm-3-4-x-3-4-bsp.html
Can anyone confirm this choice as correct?

[The Family Cyclist]

Disclaimer...it's a few years since I've dealt with this stuff but think the below is correct

Basically black is obsolete although possibly some lesser known companies then philmac still produce. It had thicker walls then the blue pipe so no need for inserts

Now iirc your could get 20mm or 25mm tap wall plates. The smaller took 1/2 inch taps the bigger took 3/4 but could be bushed down to the smaller.

I wonder if you'll need the 20mm connector for 21mm black pipe. Do you have a local agricultural merchant or plumb centre/wolseley as this will sell and if you have a bit of sacrificial black pipe can check what actually fits

However regarding the universal bit what that means is they stopped loads of inserts you previously needed to fit black pipe into modern fittinga

[aidan.f]

You are right about try before you buy, I will visit Wolsey. The wall plate is  3/4" repair attempts (not by me) damaged the pipe.

[rafletcher]

Disclaimer...it's a few years since I've dealt with this stuff but think the below is correct

Basically black is obsolete although possibly some lesser known companies then philmac still produce. It had thicker walls then the blue pipe so no need for inserts

Our black mains incomer in Coventry certainly had an insert to prevent crushing by the compression fittings. Fortunately this was 35 years ago and the plumbers merchant in Earlsdon had adaptors in stock to go to the blue pipe.

[aidan.f]

I have found stock of inserts and olives. It appears that some plastic clamp on fittings require inserts, others don't. Have fully briefed my friend who has taken on the repair.