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  1. timmyc00

    Cavitation or deadhead?

    the water freefalls onto the surface on the sump, but it falls about 3' in front of the suction line. The perforance curve i have is for the goulds 3796 3x3-13 with a 12 1/8" impeller and 1770 RPM. Looking at the curve it seems like i am right on the pump curve at 137' head at 80 gpm.
  2. timmyc00

    Cavitation or deadhead?

    BigInch, I think the suction pipe might be too close to the bottom of the pit. Do you have any resource with info about this? This could be the source of cavitation, but can a pump cavitate with a severely throttled discharge valve?
  3. timmyc00

    Cavitation or deadhead?

    This is not a submerged sump pump. When the level climbed 1 ft the difference between the level of the pump and level of the water was 9' instead of 10'. Amps also went up on the motor as expected. I wouldn't expect the intake streams to interfere with each other.
  4. timmyc00

    Cavitation or deadhead?

    it is 10' from the pump intake centerline to the water level
  5. timmyc00

    Cavitation or deadhead?

    It is pumping something because the level stays constant even though there is water being dumped into the pit. I let the level in the sump climb up about 1 foot by shutting off the pump, then turned the pump on and it discharged at 40 psig (which it was designed for) and wasn't cavitating...
  6. timmyc00

    Cavitation or deadhead?

    The problem I'm worried about isn't the deadheading, it's the cavitation. I will worry about the deadheading later. Apparently these problems have existed since the pump was installed
  7. timmyc00

    Cavitation or deadhead?

    I found an impurity in the water whose vapor pressure is about 7 psig at these conditions. However, it is only in the range of about 0.1% of the fluid. Can this boil out and cause cavitation?
  8. timmyc00

    Cavitation or deadhead?

    I shot an IR thermometer on the pump casing and it was around 72 F. The NPSHa if the water is 70 F is... 34 - VP of water@70 F - 10' ~ 23'. The NPSHr of the pump is 10'. To get to 10', my water temperature would have to be 170 def F. That is the only temperature I see it being able to...
  9. timmyc00

    Cavitation or deadhead?

    I have a sump pump pumping from a pit below the suction line with a center to center height difference of 10'. The pump is a Gould's 3796 MTX 3x3-13 with a 12 1/8" impeller running at 1765 RPM on a 20 hp motor. The service is water at 70 deg F. The discharge pressure directly downstream of...
  10. timmyc00

    Sump pump discharge head

    the old switcheroo...stars to johngp and snorgy thanks guys
  11. timmyc00

    Sump pump discharge head

    to clear up, the gauge right before the impeller on the suction side is reading -5 psig
  12. timmyc00

    Sump pump discharge head

    right..the pump has to lift 12' of water from the sump below. thanks biginch, that makes sense
  13. timmyc00

    Sump pump discharge head

    I have the discharge pressure on a gauge downstream of the pump. I know the suction head at the impeller that also has a gauge and I have the pump curve. So I basically add the discharge and suction head, and that number is where I am on the Y axis of the pump curve...correct? So if the...
  14. timmyc00

    Sump pump discharge head

    I am new to centrifugal pumps. I have a pump above a sump open to atmosphere by 12'. There is a pressure gauge on the discharge of the pump reading 40 psi. When I look at the pump curve, do I add in the 12' of head to the 40 psi, or just read the 40 psi? Also, when the level drops in the...

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