How to tell flow & return on rad pipes All aspects of plumbing questions and answers, help, tips and information

[dajome]

I have a solid floor with live radiator pipes coming through - they both have identical standard valve heads on them and I want to put a radiator on - any easy way of telling which is flow and which is return?

[nitro23456]

the flow pipe heats up first obviously.

[htg engineer]

Flow gets hot first.

Htg

[dajome]

Thnx for replies guys - there's currently no rad attached and valves are turned off. Not sure of pipe run as under concrete but length will be several metres of 15mm - not sure heat will reach. Bit late after attached radiator cos need to make sure I get the TRV on right side first time.

[nitro23456]

With the heating on you should still be able to touch the pipes under the valves.

Normally (but not necessarily!) the flow is on the left as you look at the rad.

What is the orientation elsewhere in the house? it is likely (but not necessarily!) going to be the same.

Failing this, I cant see what else you can do apart from fit a raf with your current valves.... find out which is which with the heating on.... and then change for a TRV

[htg engineer]

If there's no radiator connected the pipes wont heat up as the water is unable to circulate. So the above posts not really much use.

Check the TRV instructions, there's many on the market that can be fitted to either the flow or the return.


htg

[nitro23456]

mine do.

Its a process known as convection and the heat will still pass through from the flow and return pipes on the circuit.

[chris_on_tour2002]

most modern TRVs have no orientation, you can fit them on the flow or return and they will work. check the specification of yours as this is probably the case.

[dajome]

Thanx for suggestions - I've got some 15mm polypipe somewhere so I'll just connect that between flow and return to create a circuit and as suggested, see which side gets hot first.
Many thanx

[bobplum]

good morning
you could open one valve at a time catch the water in the bucket,time it see which heats up fastest
you can also buy trvs which can be fitted to either pipe so it wont matter which is flow or return myson i think do them
bob