Centrifugal Suction Leak Question

Discussion in 'Pumps and Tanks Well Forum & Blog' started by gritres, Jul 3, 2011.

  1. gritres

    gritres New Member

    Messages:
    56
    Location:
    nw florida
    I've got a centrifugal and a leak on the suction side (small trickle of air bubbles). The drop line is fresh poly, the leak is most likely in the joints between the poly and the pump, however, it's been hell trying to find the leak and I'm redoing joints left and right and running out of shaving cream.

    My question is this: if the drain plug on the bottom of the centrifugal didnt have a good seal would that produce a water leak or a suction air leak? Seems like it'd leak water from what I know about the way the pumps work but I've never opened it up to see exactly how the impeller works in there so I'm curious if anyone had any insight.
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,062
    Location:
    NW Ontario, Canada
    A suction leak does not always manifest as a drip when no suction is present. As for the drain plug question, if you loosen it up, does the shaving cream get sucked into the threads?
  3. gritres

    gritres New Member

    Messages:
    56
    Location:
    nw florida
    i was trying to avoid empirical testing but i guess thats the only way to know for sure

    another question: if i was having cavitation issues at the impeller would i still see the bubbles caused by it in on the pressure side or does the water vapor all condense once it hits high pressure?
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,062
    Location:
    NW Ontario, Canada
    Bubbles are air, not water vapour. The water vapour returns to a liquid state in the absense of a high temperature or vacuum to sustain it as a gas.
  5. gritres

    gritres New Member

    Messages:
    56
    Location:
    nw florida
    it's definitely not the drain plug either, it's high pressure and squirts out water when i loosen it. probably my pipe doped galv -> iron
  6. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,330
    Location:
    Houston, TX
    On a lot of pumps the drain plug will be in a vacuum when the pump is running, and be under pressure when the pump is off.

    You could hook up a vacuum gauge to that port and test the pump for suction problems.


    DonL
  7. gritres

    gritres New Member

    Messages:
    56
    Location:
    nw florida
    just to confirm the test was done while the pump was on. since it's likely toward the outside of the impeller on my pump it makes sense that it's pressure during and after operation.
  8. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
    If the pump sounds like it has gravel inside while running, it's cavitation. Cavitation will cause bubbles in the outlet if placed in the bottom of a bucket of water. You could be experiencing a high lift or plugged well screen. To know I usually install a vacuum guage in the suction line. If it reads more than 21 you have a lift problem or partially plugged well point or screen. If the needle quivers, you have a suction leak. Occasionally a pump seal will suck some air if it's a high lift. NOTE: It's a good idea to have the pump as low as possible. In developing countries people with a lift problem place the pump in a pit nearest the water level as possible. Near Alma, Arkansas we used to tie 4 wells together some 60 feet and 10 to 12 feet deep, then install the pump 10 to 12 feet below ground to reduce the lift for irrigation of bottom farm land along the Arkansas River.
  9. gritres

    gritres New Member

    Messages:
    56
    Location:
    nw florida
    ya it must just be a small suction leak from heavy lifting, the pump is not making offensive noises. i'd love to dig a pit for extra efficiency but im afraid of it getting flooded. we can get a truckload of rain at once here and be inundated in no time.
  10. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Grey PVC cement is a good alternative to shaving cream, and let it harden. Looks stupid, but it works.

    If the barbs are PVC and you didnt sand the cast line off the barbs, that will do suction leaks quick
Similar Threads: Centrifugal Suction
Forum Title Date
Pumps and Tanks Well Forum & Blog centrifugal start/run switch not engaging Aug 31, 2014
Pumps and Tanks Well Forum & Blog Centrifugal vs jet for pressure boost Jul 18, 2014
Pumps and Tanks Well Forum & Blog Centrifugal sand filter/CSV questions Mar 31, 2014
Pumps and Tanks Well Forum & Blog For Sale: Grundfos Centrifugal Pump with Baldor Motor Mar 29, 2014
Pumps and Tanks Well Forum & Blog confusing data sheet re: centrifugal/jet pump Aug 3, 2013

Share This Page