Jeff Layman wrote in newsjs58r$o1i$1@dont-
email.me:

On 01/08/18 11:33, Tim Lamb wrote:
OK so I finally got around to installing some toilets.

An earlier decision to use mains water is leading to noise where the
isolator valve is used to control cistern water flow to less than the
overflow will handle.

Any suggestions? An inline restrictor of some sort?

I'd be interested to see an answer to this too. When we replaced the
bathroom basin taps with 1/4-turn ceramic ones, I'd forgotten that it
would now be simple for "little hands" to turn the tap on full. As it is
at mains pressure, you can imagine the result of doing that! So I also
use the isolator valve to cut the flow right down. But, as you say, it
is very noisy.


Look at "Pressure Reducing Valves" on a plumbing site.