I put I 0-to100 p.s.I. gage on my water line and it pegged the gage. Can this be possible?

If the gauge is reliable AND Accurate it is.

Where did you test the pressure? On an unregulated water line, i.e. before the rergulator, water normally runs 100-150 PSIG. Inside the house should be another story. Test the pressure at a laundry tray or on an outside faucet AFTER the regulator. Should ber 60PSIG +/-. If the regulated pressure is over 100 PSIG, you need to adjust the regulator or possibly replace it.

The average house water pressure is 45 PSI. ( That's why water towers are 100 feet high) with 80 PSI at the upper limit. High water pressure puts a strain on the water pipe fittings and your valves and faucets. I take it that you have a PRV (pressure reducing valve) installed. You should reduce pressure at this valve. Do you need instructions on how to do this? Back to you, nTom

Depending where you are - yes, your pressure may be well over 100 psi. Our gauges go to 200 psi since in my area it is quite common to have incoming pressure over 100 psi. All plumbing fixtures in your house are designed to work under no more than 55 psi. Sprinklers manufacturers call for maximum of 95 psi for irrigation purposes. Do as Tom suggested. Milo