Red face day. Yesterday I tried, and failed, to replace the three elements of my toilet cistern. The overflow pipe (outlet), the siphon (outlet) and the refill entity, this one. I'll call it the inlet valve. This is where I had the real trouble. I have a 'low' close-coupled toilet, where the pan is connected directly to the cistern. The inlet is on 15mm copper, out of the wall, drain valve teed off from the feed, which is via a screwdriver controlled inline valve, which then needs connecting to the bottom of the Torbeck valve, which is in nylon. Herein lay the problem. I looked at it. I guessed it to be 15mm Yorkshire coupling... sorry, compression coupling. It screwed on quite nicely... when in my hand! [What I really needed was this]. The existing coupling was rather old and tatty... and I assumed it to be a straight through, F-F connector! I was wrong. When I rummaged around in my plumbing bits and found a new 15mm compression joint, coupled it all up... it leaked like a sieve. So this morning I called in my plumber (yes, a trusted one, not yet online), quite prepared to be laughed at. Turns out my error was in not using the right coupling. Where copper joins a tap, under your sink, seems this type of connector, known as a tap connector, is the item to use! He replaced mine with the proper type, tweaked the other compression joints as needed, and walked out. I did feel daft.

This is the item in question. He used plastic as apposed to copper.

I was looking for a drawing of such a connection to show you the difference, but I can't find one. I may sketch one, take a pic and update this entry... if I make time.