They come in 15mm and 22mm compression.
Where do I install a pressure REDUCING VALVE?
In the mains cold water feed
before the component that requires reduced pressure. You can even fit a pressure
reducing valve directly after the mains water stop cock to allow control over
the whole premises pressure
How do I install a pressure reducing valve?
These valves are very easy to
install. Isolate the water supply and cut the pipe where you want to install the
valve. Using an adjustable spanner and some grips, tighten the compression
fittings on either side of the valve. Wrap some PTFE around the thread of the
valve gauge and wind it into the main valve body. On top of the valve is a
screwdriver slot. According to the direction arrows, rotate the screw to achieve
the desired pressure.