I'm attempting to confirm which of the two pipes of my central heating spur is the flow and which is the return.

The advice I've found so far says to look for marking: RED marking (either tape or valve handle or something else) etc show it to be flow, BLUE/no marking for return. Or run the heating and the FLOW pipe will get hot first.

However, I have a pair of pipes which are a spur off my heating loop, which are put in place to connect to my under floor heating. Neither of them have any water flowing in them at the moment (so neither get hot), as the heating has not been fully installed. How do I make sure I connect the flow to the correct side of my under floor heating pump?

  • 1
    enable the flow and test ie find out which one gets hot first.. a "dummy" loop can help with this... – Solar Mike Sep 12 '19 at 10:18
  • So effectivly do a loop back, connecting the two pipe together? That might be a quite a fiddly job due to the location, and I wonder if it will be obvious which pipe gets hot first when they're so closely coupled. - But that is the only plan I've got so far. – Puffafish Sep 12 '19 at 10:33
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    Use a long coil of pipe or hose to connect them, and it will be more easily obvious. A shorter pipe/hose routed though a bucket of ice-water might also serve the purpose. Meanwhile, remember to curse the installer for not marking them in the first place. – Ecnerwal Sep 12 '19 at 13:15
  • A thermocouple probe would be what I would use the hotter of the 2 pipes would be the supply and the cooler the return. There is always a difference. – Ed Beal Sep 12 '19 at 14:29

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