I noticed that one of the underfloor heating flow meter red indicators (see pic attached) constantly points to (nearly) 3 L/min (see the picture attached), even when heating is not in use; Other indicators will move back to zero when not being heated. I am a bit concerned. Is it shown some leaking in underfloor heating (although no visible leakage)? Or inefficient underfloor heating? Is it normal? Please advise. Many thanks.