But the OP has said that it's in parallel with the hot pipe that goes to the pump.chrishutt said:Are you so sure about that, when we don't even know what it is?Softus said:OK then. So you could just ignore this device.
It could be two small pressure vessels, mounted end to end, one off the hot side and one off the cold, but with no water connection between the two (the black bit being the housing for some sort of sensor).
Tell me about it - good luck with that one.Unfortunately the OP refuses to show us enough of the installation for us to see how it functions.