I recently had someone resurface my pool. During the resurfacing, they noted that the skimmer was not holding pressure per their test (long story short, these guys weren't 100% reliable and wanted a 3rd party's opinion).

After filling up the pool, the old pool pump (discontinued model) wouldn't prime. I installed a Hayward Super Pump and attached CPVC/PVC valves around it. Initially, it was observed that the PSI gauge would shoot and float to around 30 PSI and there were some bubbles coming out of the jets. The skimmer seemed to have an extremely small amount of suction alongside the pool jets to the point where it was unnoticeable to most. Water was still flowing through the pump though.

I've already run an in-scent test around the outer piping to identify if any air was being leaked into the pool without anything being obvious. I also shut off multiple paths via the diverters to see if anything caused the pressure to stabilize. Sometimes there were minor 5 PSI fluctuations. For the most part, the PSI remained at 25-30.

My biggest fear is that I have an underground piping leak causing air to get into the system. My theory is there's a leak between the pool suction and the pool pump.

Any guidance to an assisted answer or anything I can try would be helpful. I did already try to blow out the lines with a shop vacuum to check if there was any debris blocking the water flow. It seems that the air went through the pipes just find and shot the water up wherever appropriate.

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  • Pool novice here, when water is sucked up by a skimmer, where does it go after that? Watering the yard? The sewer? Any chance that outlet could be plugged up somehow? Feb 2, 2019 at 17:58
  • @Harper water goes skimmer -> pump -> filter -> pool Feb 2, 2019 at 18:00
  • And somebody just made changes on the last one. Any chance the filter-> pool route is impeded? Feb 2, 2019 at 18:43
  • 1
    Air bubbles are a leak on the suction side of the pump and don’t have anything to do with the pressure being high. Where is the pressure being measured? If it’s a gauge on the filter is the filter clean? What type of filter is it?
    – Tyson
    Feb 2, 2019 at 19:11
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    Suction side leaks result in air bubbles, pressure side leaks are pipe dribbles. The union where the pump connects would be my first guess since you took it apart, don’t over-tighten it tho instead clean/replace the o-ring and where it seats and add magic lube or non-hardening plumbers paste. If it’s an underground leak you can isolate that with suction side diverter valves (I bet it’s the o-ring on the pump union tho). Increased pressure is probably higher flow rate on new pump, is it variable speed? If so, just slow it down.
    – Tyson
    Feb 2, 2019 at 20:10

4 Answers 4


2 hp is WAY too big for that system. That looks like a 90 sq ft cartridge filter (C-900) which can handle up to 90 GPM when clean but that is extreme. 25-30 PSI is probably not out of the "normal" range for 2 hp. You don't say how many gallons the pool is but that should determine the size of the pump. You get far more efficiency and better filtration with a slower flow. General rule of thumb is smaller pump, larger filter. More power is not good when talking about pool pumps. In addition, it looks like your piping is 1 1/2" PVC. You can only force so much water thru that small of a pipe. Think of trying to blow a mouthful of water thru a soda straw. You will encounter pretty substantial resistance. That's a small version of your pool pump...that resistance, called "head pressure" or "friction loss" converts to PSI at the pressure gauge.

The real solution is to downsize the pump. If you don't want to spend the money since this one is new, you can refit it with a smaller impeller, maybe a 1 hp impeller. For a Super Pump (with the square lid) that would be SPX2607C. If it's a round lid, then it's a Super II and would call for an SPX3007C.

PS Air in the system generally lowers pressure, not raises it.

  • I purchased a 125 square foot filter to plug in and want the higher hp for my own reasons. With that being noted, the intake has 2 inch pipes. Return lines are 1.5 inch. The current is 90 square feet which identifies right around the GPM calculation for the pool size (around 23,000 gallons) rather above the calculation like it needs to be Feb 7, 2019 at 16:25
  • Removing the filter places the psi at 15, which indicates the pipes should be fine for the flow, but the filter is a blocker Feb 7, 2019 at 16:29
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    A clean cartridge should run between 8 and 15 psi. No cartridge should run less than that. A 23,000 gal pool should circulate around 32 gpm for a 12 hour turnover, Even for and 8 hour turnover, you only need 48 gpm. Think about what your telling me...your pulling water in thru a 2" Pipe and pushing it back thru a 1 1/2" pipe. That's like squeezing 2 lanes of traffic into one lane...you're going to have a backup! (i.e. more pressure) BTW an 2 hp pump would not even pass inspection in my state unless you're using 3 inch pipe!
    – Hank4Pools
    Feb 15, 2019 at 12:34
  • what you’re saying doesn’t match what any pool store or pool website has informed me: inyopools.com/Blog/can-go-higher-horsepower-pump. inyopools.com/HowToPage/…. Feb 15, 2019 at 12:38
  • For the most part, with about 30 feet of pipes (Head) and around a 25,000 gallon pool. The gpm should be somewhere around 90-110. For suction, a 2inch pipe should be more than enough. Ignoring that there’s 2 exit 1 1/2 inch lines that can feed their own flows (and could be coupled by a 2 inch pipe) hy-techroofdrains.com/water-flow-through-a-pipe general flow calculations notes that a 1 1/2 inch pipe can hand the gpm just fine for a 2hp pump 😁 Feb 15, 2019 at 12:42

When removing the filter from the pool pump, the air bubbles disappeared leading me to believe that the water flow was either too heavy for the filter, or the the filter was blocking the flow in general (or the filter is getting air inside).

  • As an update, upgraded the pool filter the 175 square feet and everything is perfect 😁 Feb 17, 2019 at 14:20

I use two Hayward Super pumps. They are incredibly powerful and can suck air into the system where that old pump probably wouldn't. Make sure the two screws on the lid are extra tight. I would even use some Swan grease or other lube to help seal that area. Checking and resealing every point on that sand filter would be a good idea. For instance, why is there a plastic bag wrapped around the inlet side of your sand filter? Is there a leak there? A leaking gasket in the filter can also allow air to enter the system. If it's been a while since the "O" ring or gasket has been changed, it might be time to change that out. Check the bleeder valve also. Leaks happen there a lot. Make sure the water level in the pool is at least 1/2"-3/4" above the skimmer inlet.

  • I put the bag there just in case.. it does nothing. It’s also not a sand filter. Already checked for airleaks and gaskets, all if good there. Feb 7, 2019 at 20:47

It will only leak water when you shut down the system .while system is in opperation it will not leak on suction side it just takes aor into the system. Leak pn return then it needs to be addressed. Your pump is running effeciently i would leave it alone. The pressure fluctates because of the leak on suction side not big deal most people dont even notice when they have one so the technians dont even bother fixing them. Lot of time and money for getting rid of a few air bubbles

  • Sorry, it makes no sense to me Aug 12, 2023 at 1:18

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