Suction Side Problems: Air Leaks, Bubbles in Returns, Pump Won't Prime, etc.

[ADMIN: The new suction leak sticky is here: http://pool9.net/leak-s/ ]

We have fairly regular questions about suction side problems with pools. But answering those questions is fairly tricky, because the list of possible causes and problems is very long.

So, I spent several hours today cataloging some old threads on the topic. Here they are:

• Suction leak causes pump priming problems
• Suction Air Leak Causes Skimmer to Spew
• Suction side leak . . . Found in Pump Drain Plugs
• Air Bubbles from SWCG
• Air coming into pool through jets
• Air Bubbles in Return Lines
• Pump Sucking Air; Won't Prime - Needed to be primed
• Suction Air Leak Cause Filter Bleed Off Issue
• Air bubbles in return jets
• Air in system won't let pump hold pressure (Skimmer weir stuck)
• Help, suction leak!! (fixed with new pump lid o-ring)
• Air Leak? (from bad O-rings in Jandy valves)
• Suction Leak Causes Pump to Run Dry
• Can Small Leak Prevent Pump From Priming?
• Air bubbles coming from return (from crack in pump pot)
• Finding a suction leak
• How To Test for Air Leak? (found - tree root grew into line!) Wow!
• Suction side leak (PIC) am I close???
• Air bubbles - finding leaks with a stethoscope
• Gradual loss of suction while vacuuming
• Suction Leak Causes Pump to Lose Prime

list of threads: 19841, 16560, 16813, 13964, 11811, 11332, 11203, 10901, 10022, 8713, 8608, 8324, 8006, 7872, 7484, 6337, 5455, 5304, 1499, 487

I went through each of these threads as I have a suction side leak. My problem is slightly different though. I get bubbles out of the outlets and twice now my pump has lost prime. However each time after I backwash it primes fine again. I just changed the sand in the filter a couple of weeks ago. Is it possible that the new sand is working so well that it loses prime?

I usually backwash every 2 days or more if I'm vacuuming.

I can't think of a series of causes and effects that would result from your change of sand, and lead to a suction leak.

Oops. I thought of something.

It *is* possible that your new sand has lowered back pressure (really, resistance to flow) on the output (effluent) side of the pump. This would in turn lead to higher overall flow, and thus increased negative pressure on the input (influent, suction) side of the pump. That might, in turn, stress a pre-existing weak point in your suction lines or valving, and possibly increase the damage or opening there.

But, it still comes down to there being a leak in the suction side piping and valving. The sand might have triggered a worsening of the leak, but it didn't cause the leak in the first place, and is not related to the location of the leak.

By the way, you do not need nor want to backwash every two days or even every time you vacuum. You only backwash when the pressure rises 8-10psi over clean filter pressure.