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Galvanized pipe is main feed, corroded at copper junction.
I'm in Baltimore city. Moving into a townhouse built in 1928. the inside plumbing is nearly 100% copper (or so it appears) Nice work, good solder joints, parallel runs, Type L, 1" main runs. The feed to to the house is a large Galvanized pipe, the OD measures 1.683 inches so I assume it is SCD 40 1&1/4 pipe.
Naturally, where the galvanized meets the copper 1" main in the house, it is corroded badly. Pressure gauge on the inlet side reads 120psi. PRV (Watts N35B 1") outlet side reads 120 psi also when static, but goes down to 40 psi when water is running.
I know this is a problem waiting to happen and needs attention. I ask for sharing of wisdom.
1) I am more inclined to replace the PRV rather than rebuild - considering a Watts 25AUB-Z3 1", but looking for advice here. I am nervous about undoing the lower union nut with the corrosion from electrogalvanization about a foot below this joint. If I replace, is that an ok PRV or should I consider something else.
2) Most importantly I know the main feed should be replaced. It goes under a small stone patio and a piece of sidewalk but appears to be a completely straight run of only about 35 feet. What would be the correct size and material to replace the main?
3) can a digging Mole (horizontal trencher) go from the house out to water valve? there seems to be room in the basement to do this, and it would avoid ripping up 10 feet of the patio. on the other side the water meter is on the opposite side of the sidewalk.
Please help me to make sure this is done correctly - thank you!