DIY Doctor UK DIY Forums

My mothers central heating system consists of two loops with each of the radiators sat on the loop pipe (yes old design I know).

The penultimate radiator on one of the loops struggles to get warm over it's whole surface. generally warm vertically around the inlet pipe. (it has been bled)

It is fitted with a TRV on its inlet. but it is as if the flow along the loop pipe beneath the radiator is preferable to flow through the radiator.

I obviously can't restrict the flow through the loop as this would impact all the radiators especially when the TRV shuts on this one. Is there some form of differential pressure valve which could be fitted in the line under the radiator to direct flow through the radiator in preference to the loop but not impede flow when the radiatr's trv closes?


Any ideas greatfully received.

Remove themostat head (should only be hand tight) and check the valve pin is free to move in and out - dont pull it, push it. If this does not work try turning down the lock shield valves on the other rads just a little at a time an see what happens. Good luck - one-pipe systems suck!

Thanks for the pin tip. I'll give that a go next time I'm down there.

Not sure how closing the other rads down will work, the temp of the loop under the rad is reasonable, but any port in a storm ;-)