Several years ago we had our water heater replaced. At the time, the plumber said that our regulator wasn't working and he replaced it. It could have been not working for decades but I never had a problem from the high pressure. About a week ago, I bought pressure gauge (I don't know why I waited so long to get one). I measured the pressure at a hose bib in front of the regulator and it read 100psi. I checked the pressure at hose bib behind the house which I know is after the regulator, and it read 100psi there too. I figured that this newer regulator was toast. Again, I don't know how long ago it went bad and I don't have any problems in the house. Just for grins, I tried adjusting it, thinking it wouldn't help since it was beyond the 75psi upper limit. As I suspected, I still got 100psi at the rear hose bib. The weird thing is, I checked the pressure at the bathroom basin, and found that the adjustment had made a huge difference. I had to readjust the regulator to bring the pressure up to around 60psi at the basin. Any idea why the adjustment affected the bathroom faucet but not the hose bib?