Upon arrival I was told that we had pumped loops up to 55psi LWP running and customer is concerned of leak. During diagnostics I found LWP at 13psi. Neither system has faulted. Checked all piping indoors and found no leaks. Used pump to pressurize loop to 50psi, burped pumps then found pressure slowly dropping 1psi every minute or so. 2 units but 1 flow center, FC2G-023371. Need to return to install water meter, speculating outdoor loop leak.