In article ,
"Dave Plowman (News)" writes:
In article .com,
Digby wrote:
Does it matter which way round the water flows through the system ?
Is the there any simple way to discover if I have them the wrong way
round ?

You should have an adjustable gate valve or TRV on rads usually fitted
on the flow side with a locksheild on the return. Check which pipe gets
hot from cold first at a rad. This will be the flow.

Most TRV's for some years can be fitted on either end.
I usually fit on the return side, where the pipework
will be cooler and have less direct thermal effect on
the TRV sensor. So in short, I don't believe you can
use this method to tell which is flow and return.

3-port valves always go on the flow side AFAIK.

--
Andrew Gabriel