On 12/09/2016 23:46, Chris French wrote:
I've always used TRV4s. Ne er had a problem with them. Have
Sentinel in this system, can't remember for the old
house.

Last house had TRV4s on every radiator bar one. When I got there, the CH
was untreated water. Flushed the system, took radiators off one by one
for flush in garden, used Sentinel. Topped it up every few years.

Eventually had to replace one TRV4 (with another), seemed to be a bit
"sticky". That was it.

--
Rod