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The problem is that there is no water at the outlet when pump is working. When I disconnected 3/4" pipe that was in parallel to 1" pipe, and left 1" pipe only, the water showed up at the outlet and flow was ok? What was wrong with this parallel piping? Please explain that to me.

  • Are there valves throughout this system? – Steven Jul 29 '14 at 0:52
  • How are these pipes arranged in 3 dimensions? Where does that 3/4" line on the left go? Did you remove both it and the 3/4" feed, or just the latter? – keshlam Jul 29 '14 at 1:08
  • The pump is a 1-1/4 submersible one. There is enough water in the well. 3/4" pipe that splits from 1" pipe right after the pump is the one that I capped off, and got normal flow and pressure. 3/4" outlet and 1-1/4 outlet remained same. I need to point out that before I did it, there had been no water on both 3/4" and 1-1/4 outlets. – Nirman Jul 31 '14 at 21:14

Sometimes centrifugal pumps (those with a spinning impeller) will cavitate when there is a discharge path too big to supply back pressure, and/or if there is not enough suction pressure. Cavitation will result in low or no flow, and will usually be accompanied by pump noise. You may be operating the pump outside of it's design parameters (pump curve).

See if you can recreate the "no water" scenario, then slowly close off the pump discharge partially to provide some back pressure (which is what it sounds like you did when you blocked/removed the flow path to the 3/4" pipe). If the pump is cavitating do not run it for too long like that or it could be damaged.

  • Thank you for your comment. I did not completely removed 3/4" pipe. After I removed 3/4" pipe that run parallel to 1" pipe, I still got 3/4" and 1-1/4" pipes with outlets. – Nirman Jul 31 '14 at 21:33

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