When the water pressure coming into the house runs too high, the signs show up all over. Faucets that spray when they open. Pipes that bang when a valve shuts. Toilets that keep running. In Santee homes, some regulators have worn out and some houses never had one, and the plumbing takes the strain either way.
High pressure is hard on everything connected to the water line, every joint, faucet and supply hose, and especially the water heater. When a water heater fails early, pressure is often part of the reason, and putting a new heater on the same high pressure just starts the clock over. A pressure regulator at the main brings the whole house into a safe range at once.
The contractor puts a gauge on the line and tells you the number. From there it's clear whether you have a working regulator, a failed one, or none at all. You hear the options in plain English, including what adding a regulator involves if the house doesn't have one, and the decision is yours.