How To Locate Flow and Return Pipes

How To Locate Flow and Return Pipes

The Basics:


Over the years one of the more frequent questions that homeowners ask me is how to locate which of their radiator pipes is the flow pipe and which is the return pipe. The question usually revolves around the need to install TVRs (Thermostatic Radiator Valve) at each radiator. In most cases TVRs are unidirectional. In other words it doesn’t matter if the valve installed on the flow or the return side of the central heating circuit.

When you search for a new valve make sure that you can install on the flow or return side of the circuit. If however you need, or just want to locate the flow and return side it is very easy.

Make sure the heating and hot water system is turned off and all the pipes in the house are cold. With all pipes cold switch the heating system on. Make sure to leave the hot water circuit off if you are able to do so. Some systems require the hot water to be on in order to have heating. As soon as the heating is turned on start checking the pipe work nearest the boiler for the pipe that heats up first. That should be the flow pipe. The flow pipe is the one with the pump attached to it. Start working your way around the radiators in the house and check to see which pipe heats up first. That too will be the flow pipe. Mark the flow pipes with the letter ‘F’ and you will eventually have all the flow pipes marked.

Depending on the type of TRVs you buy you will now be able to install them on the flow side or on either side as you will know which direction the water is flowing through the system.

A very boring subject indeed so if you’ve made it this far congratualtions and good luck.

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