Originally Posted by irritation
Doesn't make it right. I bet water heaters have a short life around there.
No, you don't understand. The high pressure is regulated down for the house, and USUALLY the system. Look at the photo I posted. There is probably 100-120 psi before the first PRV in the lower corner of the photo, before the meter. That PRV will regulate it down to water ever I may need for the system itself, the second upper PRV will again regulate it down to 40-60 psi inside the house, or what ever is needed. So inside house pressure is brought down to a manageable level. Water heaters, toilets, sink faucets, ice makers - would all be damaged by the 120+ pressure.