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Don't forget about the effect of ambient temperature on the system pressure. If I pressurize the down circuit in the afternoon when it's 90 degrees F, in the cool of the next morning the pressure will be near zero. I can watch the pressure climb back up to 500 -- I have pressure gauges on my panel -- as the ambient temperature climbs back to 90. Same thing goes for raising the gear when it's hot down low and climbing to a high altitude for a long cross country where it's significantly cooler. Typically, my high pressure will start out at about 1200 psi. After about an hour at 12,500 ft, the high pressure may be as low as 800 psi, and the pump may come on once to bring the pressure back up -- I've noticed that the pressure-switch hysteresis can be quite large when the pressure decreases slowly like this. I have no leaks in my system. The pressure will hold for days at constant ambient temperature.

Mike Reinath
N3602M
Std. Build 360