Search for “¼ BSP male blanking plug”

This one seems similar to the ACS part, although it’s stainless steel rather than brass:

https://www.accu.co.uk/imperial-flat-head-socket-pipe-plugs/72410-HPPF-1-4-G-A2?uk_google_shopping=1&c=3&gclid=CjwKCAjw4c-ZBhAEEiwAZ105RcbBfcmbFm3CdqxCCTCVULCUoiRsknj9xjVobOOyRYame5ChojdU2BoC3gIQAvD_BwE

and one in brass:

https://www.thehosemaster.co.uk/bspp-allen-key-plug-o-ring-nickel-plated?gclid=CjwKCAjw4c-ZBhAEEiwAZ105RRq6fcbL6Qq6d6Hm-KDE2yF2nlHWVqdW-E1o--VVtgDhup7RhcYCyxoCwsEQAvD_BwE

(No particular recommendation for these vendors; just the first ones I found)

Thanks guys ,just a note, i clicked on the link to the stainless steel plug and noticed it was 16mm long, would it matter if the replacement plug is longer . Im guessing not as it would just mean a few mill more sticking inside the boiler .

    canaryone Also, note that the plug itself is 12 mm; 16 is the total length including the head - I don’t know what ‘length’ measurement ACS took.

      Thanks Dave, CoyoteOldMan the plugs have 8mm thread length and overall length of 12mm

        canaryone Totally fine with the stainless plug - you’ll have a boiler that holds 0.132 ml less water. Or you can cut the plug with a fine hacksaw and refine the thread a bit, but I wouldn’t bother.

          canaryone Hi i am having problems with my Minima , I’ve taken the boiler off and removed 4 of the bottom blanking bolts but the 5th one just wont budge and i have unfortunately rounded off the hex head inside the bolt, and i cant turn it

          If you carefully use a hacksaw, you can cut 2 flats into the nut without going into the stainless boiler, it’s brass so will cut easily. They you can put a good fitting spanner on it to turn it. If that doesn’t work, then you can still go down the extractor route!

          Contact me

            Cheers dave good tip, i did manage to get it off by adding some heat and penetrating spray, then turning the screwhead with a chisel by slowly tapping it until it moved, and finished screwing it off with mole grips.

            11 days later

            A hypothetical question around the stainless steel plugs since my Minima has yet to be shipped.

            Would it be better to get the A2 or A4 version? A4 is fractionally more expensive by £2.30, but has a better resistance to tarnish and corrosion to the A2. Or does it not matter in this type of hardware application?

              Verion It probably doesn’t matter considering the content of a boiler (fairly low chloride/sulphate concentration), but I’d get the A4/316 version precisely because it’s only £2 more.