OK,

So I'm in the process of adding a sprinkler system to the back yard - and I checked the pressure at the hose bibs w/ a pressure gauge - 80 psi. Well, where the water enters the house (in the basement) there is a pressure reducer "set at 50 psi." I'm under the impression that the thing is not working. So my question.. .

Q.) Do I really need to worry about the extra 30 psi that now is running all through the house? Will there be any damage to the internal plumbing, faucets, toilets, etc?

I hate to install the entire back yard sprinkler system w/ an 80 psi design pressure, then find out I really need to get that PR changed out and regulated to 50 psi - just to realize my sprinkler system is then under-pressured.

Thanks -

Q.) Do I really need to worry about the extra 30 psi that now is running all through the house? Will there be any damage to the internal plumbing, faucets, toilets, etc?
When you realize that 45 PSI is the average house pressure then, yes, you are putting additional strain on all, your water pipe joints and faucets. You PRV valve is either misadjusted or faulty.
There's another issue you'll have to address when you install your sprinkler system. Local code will force you to put either a check valve nor a backflow preventer on your water service making it a closed system. This will leave no place for the water to expand to as it heats up in your water heater. This will cause leakage out the T & P valve on the heater. The solution would be to install a expansion tank, (see image) on the cold water supply to the heater. I'll put up a image showing you how they're installed. Good luck, Tom