Plumbing – Would Replacing an Existing 3/4“ Water Main Line with 1” Improve Overall Volume/Flow to House (GPM)

If you are on a municipal system and have pressure that high, you quite likely already have a pressure reducing valve (PRV) installed near your water meter. The International Plumbing Code requires PRVs on any water supply over 80psi. If this is the case, your PRV may just need adjustment. As they age, the spring regulating the device's operation can soften. Or it could be faulty and need repair or replacement. If you do not have one, you need to have one installed.

If you are on your own well with a pressure tank, the pressure switch controlling pump off operation needs adjustment. Other types of systems should have similar arrangements to control pressure.

How to adjust a PRV. There is typically a bell shaped housing with an adjustment screw and lock nut on top. Loosen the lock nut and turn the adjuster counter clockwise a small amount. The adjustment can be rather sensitive. Operate the faucets and toilets in your house to allow the system to equalize to the new pressure setting. Take a new pressure reading. How much it changed will give you an idea how much more adjustment is needed. Typical water system pressures should be somewhere in the 40-60 psi range. Shoot for the high 50's.

If the PRV controls supply to a fire sprinkler system (it normally shouldn't), you will need to check with a fire supression professional to determine if and how much you can reduce the supply pressure.

If you do need a new PRV, check with your municipality, they sometimes offer rebates to help mitigate some of the cost.

B2 is a bypass valve. B1 and B3 are so you can remove the water softener to replace it and still have water pressure in the house. B2 (only) or B1, B3 (only) should be open at any one time.

"All the way to the right" (wound in clockwise) is closed on a standard valve. "All the way to the left" (wound out anti-clockwise) is open on a standard valve. You may also be able to see the stem (behind the valve handle) go in/out as you wind it (in is closed, out is open.) Some valves may not have visible stem motion.

The system is not foolproof, since you can have valves open that should not be open at the same time, yet it's (last I knew) code in Massachusetts, which does not allow the use of a foolproof, or at least fool-resistant, bypass valve as usually supplied with new water softeners, and successfully used in 49 states that are not in thrall to antiquated plumbers.