Low water pressure

[Davva]

I recently had the supply pipes from the street to the house replaced and now my water pressure is a lot lower.
The guy that replaced the pipes said that the pressure at the house was 125PSI and that I should fit a PRV. I did this today and now the water pressure is very low.
The PRV is set to 50PSI but I believe it can be adjusted up to 80PSI.

Given that the old pipes had no PRV and I had the gate valve open all the way, is it safe to assume that I can set the PRV to max without causing any pipes inside the house to rupture, split, leak or whatever old pipes do under pressure?

[Caduceus]

I wouldn't recommend setting the PRV above 65 psi. The problems that are caused by excessively high pressure are not always immediate. Toilets are usually the first victims, but any appliances that have solenoids to open/close the water supply can suffer unseen damage. With the installation of a PRV and/or a backflow preventer, it is also recommended to have a thermal expansion tank installed on the cold supply to the hot water tank. Be sure that the thermal expansion tank is pressurized with air to match the incoming water pressure. Thermal expansion can do the same damage as high pressure. Some plumbers cite the bypass on the PRV as enough protection from thermal expansion, but it truly doesn't do the job, especially if a back flow device is installed.
There is usually an adjustment period when something changes in your water system. Your plumber should explain this to you before installing the new service and installing the PRV. It is also important to check the aerators and shower heads to see that they are clear of debris and not affecting to volume of water at the fixtures.
Experience #1. Service call for "Water shuts off to clothes washer".
Customer states that sometimes the new washer gets no water and will also shut down between cycles. To resolve the issue she has to open the laundry tub faucet and the washer starts to fill again. Problem: high pressure and thermal expansion, failed PRV. New PRV and TET installed. Appliance performs normally now.
Experience #2. Service call for "Leaking hot water tank". I arrive at the same time as an appliance repair tech. He is there for a warranty repair on the dishwasher. We both head to the basement, he is the first to check pressure. Pressure was 130 psi, no regulator but back flow was on service. He informed the customer that the warranty is now void on the appliance and will have to charge full price to repair the dishwasher. The leaking T&P valve on the tank was also caused by the situation.
When altering or adding to any water distribution system there is always a chance that solving one problem can result in creating one or more issues. It's important to have a complete assessment done by a registered plumber and ask lots of questions if you have any concerns.
I hope this long-winded reply answered your question and gave you some insight as to what to expect from future plumbing services.