One of our showers has an intermittent leak, and I've figured out that it happens when the hot water heater is on. There's no expansion tank on the cold supply side for our hot water tank, so I'm guessing that the increased pressure while the heater is on is causing the leak.
I picked up a cheap water pressure gauge and measured the cold water pressure at a slop sink in the basement at 100 psi. Presumably that gets even higher when the water heater is on.
I had been thinking that an expansion tank would solve this problem, but now it seems like the water pressure is just too high in general. Do I need something else? Should I just repair / replace the shower faucet and leave the pressure alone?
EDIT: There's definitely no pressure-reducing valve inside the house where water service enters. Our water meter is outside near the street, under a small manhole cover. Might the PRV be in there as well? I couldn't find an obvious way to get into it, perhaps I need a crowbar or something? Municipal water service was installed at this property relatively recently; prior to that it was on well water.
EDIT 2: I've measured the cold line as high as 170 psi while the hot water heater is on. So clearly this is way too high.
My meter is by the street, under this cover (gloves for scale):
Is it possible there's a PRV in there? I couldn't pry the lid off with a screwdriver. Do I need a special wrench for one of those fittings to get in there? Am I even supposed to open that thing?