i have bare pipes coming through the floor for my radiators how do i figure out which pipe needs the thermostat on

the one that gets hot first is the flow most modern stats will go flow or return

Hi, As a rule of thumb most thermostatic valves work on the return of the system. Check the valve itself and there should be a little arrow near the outlet. If the arrow points away from the valve it needs to go on the return side of the radiator, if it points into the valve it should be on the flow side. How to tell flow or return?. Turn off the boiler and let the system go cold, turn it on again whilst feeling both pipes into the radiator the one that gets hot first is the flow, the cooler one is the return. Happy fixing. Guy.

When you turn your heating on, the pipe which heats up first is the flow and your valve should go on this side of the radiator. However, you can now purchase bi-direction or reverse flow valves which can go on either side of the radiator. Regards, Alex.

Hi, Most thermostats are bi- directional and will work on either flow or return. Hope this helps.

Nearly all thermostatic valves are now bi directional so both they can go on either end now.

Hi, Most valves are dual flow, so it does not matter so much where you install your TRV. I suggest you put it on the side that will not be obstructed by furnitur, curtains ect and can be easily adjusted. Dont forget to clean your system when you empty it and then top up with an inhibutor. Regards Dean

Radiator thermostats nowadays are universal and work on flow and return

Hi No need to worry most thermostic radiator valves work in both directions flow or return, you can see on the valve body that the arrow will go in both directions. I hope this helps Dave

use a plumbase trade valve which can flow either way

buy reversable TRV's, these go on either the flow or return and will work perfectly. They are only a little extra and the pin wont stick as much as time passes. Good luck David Oliver

you should put the thermostat on the flow pipe to the rad ,,you can find this out by when you turn on your heating the pipe on the rad that gets hot first is the flow pipe ie the water is travelling through that side of the radiator first then through rad and out of the other end pipe ,,return pipe ,, so basicly the hotest pipe to the rad is normally the flow side ,, hope this helps regards richard taggart

Hi Adam, Today you can fit a thermostatic radiator valve to either pipe, they are reversible, just ask your plumbing merchant for the correct type. Otherwise you can switch the heating on and go around each radiator and feel the pipes. The one that gets hot first is the flow. This is the one to fit the thermostat to. Good Luck Sincerely Martin Hislop

Turn on your central heating and see which side heats up first. That side will be your flow and the other side will be your return. By putting the thermostatic valve on the flow side you can accurately control the temperature through your radiator.

The one that get's hot first.