The pressure gauge on our new sand filter failed in its second year of life. When the pump is off the gauge reads 20 lbs. On the advice of a friend who's really into DIY irrigation (bored 500 ft well, installed his own drip and full pressure systems) I bought a "liquid filled" gauge from Northern for $12.95. My friend has run his liquid filled gauge for 8 or ten YEARS without failure.
Seems like a good replacement for the usual piece of c**p that the pool stores sell.