Pressure loss

MWunsch995

I have a closed system with two zones. Last few days every time my bigger zone turns on (calls for heat) the pressure in the system drops rapidly to 0-5 psi. I know 15 is normal psi..I usually have mine at 20-25 since one of the manifolds has had a slow leak since install. What can be causing this pressure drop??

HomerJSmith

It could be where the relation of the gauge is to the pump.