We have low water pressure: the garden hose nozzle projects water about 8' horizontally. We have old 1/2" galvanized pipe which is likely clogged with rust. A 6' section of this pipe leading to the outdoor faucet was recently replaced with no improvement. The plumber said the pipe from the street is probably clogged and should be replaced. The estimate for this is 00. It was replaced about 40 years ago with more 1/2" galvanized. We also had a rust-through leak in a bathroom pipe a few months ago, which was patched.
Can I increase the pressure by adjusting the pressure reducing valve? Is this more likely to cause a leak that replacing the pipe to the street (which would also presumedley increase the pressure in the system)?

1/2" from the street? That's really small. Street pressure has little relationship to house pressure or flow since that is regulated by the PRV. Increasing the pressure may do little if anything for flow. It will give you a quick burst and then drop off due to the decreased pipe diameter. Just think, you could have a 1/4" line with 90# or a 3/4" line with 30#-which one will yield more water?. If you decide to go with a new line, make it at least 3/4", particularly if it is any distance. I just had a 3/4" galvanized replaced with 3/4"PVC, about 70' for $1200.

Hi Bill

You keep talking about pressure when you should really be talking about VOLUME. Here, the internal diameter of the old galvanized pipes has probably been choked down from a 1/2" pipe to a 3/8" pipe (or smaller at certain junctions), so increasing pressure will only serve to increase pressure on the old pipes and will not deliver a greater volume of water to the fixtures.

Questions, OK?

When you removed the old pipe leading to the outside faucet was there any indication of sediment deposits? How about between the brass outside faucet and the galvanized fitting?

How is the pressure/volume of water at all the other fixtures in the home... you only mention the outside faucet?

How is the hot water pressure/volume?

Finally, if you want to know how the volume of water is at the water entering the home, you could install a boiler drain (has shutoff and hose connection) after the water meter and test for pressure and volume. If the main water supply coming in is good you may only need to replace the pipes inside the home... maybe?

Back to you...

Mark