I live in a small two story house (row home) with water service entering through the basement. The bathroom is on the second floor. Whoever did the main service line used 1/2 inch copper instead of the propper 3/4 inch, so I don't have ideal pressure. Moreover, the main shutoff valve is a globe valve, which I understand limits flow. After the valve, the rest of the main line is 3/4 inch pipe.

I don't have a water pressure problem when only one fixture is running, but the pressure drop is noticable when a second fixture is turned on.

Would it be worth it if I replaced the globe valve with a ball valve? How much difference should I expect in pressure just by replacing the valve?

  • 2
    Is the supply line coming out of the floor 1/2"?
    – HerrBag
    Mar 8, 2013 at 13:27
  • Yes. The supply line to the curb shutoff is 1/2 inch.
    – Edwin
    Mar 8, 2013 at 20:22
  • Its still worth it to replace, if only for convenience (1/4 turn 0-100%), But you'll still get 3x to 5x more flow
    – HerrBag
    Mar 8, 2013 at 20:26

2 Answers 2


YES! I came across a 10:1 flow rate differential between 3/4 ball (25 GPM) and 1/2 globe (2.2 GPM) There's almost a 50% reduction, just going from 3/4 pipe to 1/2 pipe (I inferred the pipe size flow differential by comparing 1/2" and 3/4" ball valves of the same type here). Table 2 here Compares 2" ball at 228 and a globe at 44 for a ratio of 5:1, then add in pipe diameter and 10:1 seems reasonable.

Be sure they put in a full port ball valve in bronze with drain (on house side). Full port has the least flow restriction. Bronze is safe for potable water, the drain is for future repairs to drain the lines.

  • Can you provide a link to the source of your information?
    – Tester101
    Mar 8, 2013 at 14:20

I went ahead and replaced the 1/2 inch globe valve with a 1/2 inch ball valve. Here are the results:


  • Static Pressure - 40 psi
  • With Bath Sink On - 26 psi


  • Static Pressure - 40 psi
  • With Bath Sink On - 32 psi

Although it's not as much an improvement as I hoped, I'm satisfied with having made the replacement.

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