Finding & Fixing Suction-side Pool Leaks
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Finding & Fixing Suction-side Pool Leaks
[2018 Admin note: in progress and incomplete.]
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People know that leaks on the pressure side (downstream of the pump) leak water OUT, but often are confused by the fact that suction leaks usually leak air IN.
There's a bit of terminology and pool piping lore you need to grasp. All pool pumps can be divided into 2 sides, with the impeller in between. The suction side includes the pump strainer pot and extends to the inlet or throat of the impeller. The pressure side begins at the outer edges of the impeller, and continues out the discharge pipe. Everything on the suction side will tend to leak air IN, if there's a leak. Everything on the pressure side will tend to leak water OUT. Many pumps have 2 drain ports, one at the bottom of the strainer pot, and one in the volute, which is the chamber that the impeller rotates in, and that contains the diffuser. In the diagram below, if O-ring #11 splits, the plug #10 will leak air INTO the suction pot. But if the O-ring on the un-numbered plug splits, water will leak OUT!
https://lh6.googleusercontent.com/-4...diagrammed.jpg
Suction leak symptoms- Pump won't prime.
- Air in the pump strainer basket. (visible thru #5 lid above)
- Air bubbles returning to pool.
- Air in filter.
- Poor suction.
- Pump loses prime.
- Pump loses prime when you connect a vacuum.
Not every pool with a suction leak will have all the symptoms above.
Common locations for suction leaks- Pump strainer lid. (#5)
- Suction pipe connection (#15)
(If the pump is allowed to 'run dry', often the connections on both sides will sag. If they leak, the pressure side connection will leak water OUT, but the suction side connection will leak air IN.)
- Pipe unions on the suction side. (#8 & #9)
Other unions may be present in the piping.
- Suction side valves
- Suction drain plug (#10)
- Stems on valves
- Piping between pump and skimmer and/or main drain may have cracked.
(Freeze damage is a common cause.)
- Skimmer weir (or flap) may be stuck up, causing skimmer to intermittently suck air.
There is another source of suction problems that's not exactly a leak. Off-line chlorinators, ozonators and the like are often directly connected to the pump on one fashion or another. Sometimes, the connection is directly to one or both of the drain plugs shown in the images; sometimes the connections are to the piping just before, or just after the pump. Sometimes there are small check valves or other arrangements designed to prevent unintended air or water flow.
But rather frequently, this tubing or these connections introduce suction problems that can be very hard to identify because users or service guys assume that, since the tubing was deliberately placed, that it's not the problem.
In all cases, if you have external equipment connected to, or near, the pump, DISCONNECT IT, and plug or close the connections while looking for suction problems. If doing so causes the suction problem to disappear . . . well, you've found the problem!
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Here's a list of past threads regarding suction leaks.
list of threads: 19841, 16560, 16813, 13964, 11811, 11332, 11203, 10901, 10022, 8713, 8608, 8324, 8006, 7872, 7484, 6337, 5455, 5304, 1499, 487
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