Side-entry fill valve

No different to any other side entry valve IME

Thanks. A rare post from you!

Have you tried fitting a flow restrictor?

Can't say I have. I'd always assumed they were for Torbeck-style valves. The isolating valve being used at present only controls the flow to the CW tank, so I'd assume is effectively acting as a flow restrictor anyway. but it's an idea I'll keep in mind.

Fed up with all the politics.

If it has a large DIAPHRAGM WASHER like this change it and make sure you get it the correct way round they harden with age and cause water hammer

The float valve was brand-new in November.

Next time I remove it I'll have a look at the diaphragm.

have you read the feedback on screwfix seems as if PEGLAR have some quality issues I have fitted loads of these in the past without problems and only had to change diaphragm after 10+ years so still think if you fit a new Diaphragm ( perhaps Not from Screwfix) it would cure the problem

I think it's a combination of the valve and input water pressure/flow. The original was a Screwfix "cheapie" which had worked well for about 4 years. It started to make a hammer noise a few weeks after the gas CH boiler was replaced. Coincidence?

Taking apart and cleaning the valve would improve (but not completely remove) the noise for a day or two, but then it would get bad again. I decided to replace it with the Pegler, but that immediately turned the hammer into a foghorn. Fiddling with it would again improve things for a while. In fact, once it didn't make a noise for about 4 weeks, then just started again out of the blue, and once it had started rapidly got worse.