My pressure gauge was not working so I bought a new one and thought it would be an easy change. As per instruction from my pool store:
Turn the filter off and unscrew the old gauge.
Take the new one wrapped with Teflon tape and screw into the port.
I asked them if water would come out of the port and they said no.
When I unscrewed the old one water did come streaming out but I just put new one in and tightened.
I thought all was well until I got up this morning and the pool had drained down below the skimmer hole.