Pool pump running but no water flow

Split the problem in half first

Every cause of this symptom is either before the pump or after it, and one glance tells you which.

Look at the pump basket through the clear lid while it runs:

• Full of water, no flow at the returns → the restriction is after the pump. Filter, valve, or return-side plumbing.
• Half full, or swirling with air → the problem is before the pump. Something is letting air in or blocking water.
• Empty, won't fill → the pump cannot hold prime. Also a suction-side problem, and a reason to switch it off — a pump running dry destroys its seal quickly.

That one observation rules out a whole side of the system, which is why the diagnostic asks it early.

Then read the pressure gauge

The number itself means nothing. The comparison does. Every filter has a normal clean pressure, and everything useful comes from the current reading against that.

• Higher than normal → restriction in the filter or after it. Hayward's low-flow table pairs a high gauge reading with a plugged filter or a partly closed valve, and sends you to backwash or clean the filter as its own manufacturer instructs (Hayward Super Pump 700 manual, p. 12).
• Lower than normal, or zero → the filter isn't receiving water. Look upstream.
• Normal, but flow is still weak → often the impeller, or a restriction the gauge can't see.

If nobody has ever told you your clean pressure, note it after the next filter clean. It turns the gauge from an ornament into an instrument. Filter pressure too high and filter pressure too low take each reading further.

Before you open anything

The pump and filter run under pressure. Pentair warns that air trapped in a pressurized system can blow a lid off, with serious injury possible (Pentair SuperFlo guide, p. 4), and Hayward says to stand clear of the equipment at start-up and never to move the filter valve handle while the pump is running (Hayward Super Pump 700 manual, p. 2).

• Switch the pump off before opening the pump lid or a skimmer.
• Close the suction and return valves if your pad has them, and release pressure at the filter's air relief valve before opening the pump lid (Hayward Super Pump 700 manual, p. 7).
• If the pot is hot, leave the lid on. Pentair warns that a pump that has run without water can build vapor pressure and hold scalding water; open it only once the pot is cool to the touch (Pentair SuperFlo guide, p. 4–5).

Safe checks at the pad, in order

Genuinely — several of these end the problem.

1. Empty every basket. Pump basket and all skimmer baskets, with the pump off. Hayward and Pentair both list a full strainer basket in their troubleshooting tables, and Jandy notes that debris in the basket starts to block flow (Jandy VS pump manual, p. 18).
2. Check the water level. Pentair puts the right level at about halfway up the skimmer opening; below the opening, the pump draws air through the skimmer, loses prime and runs dry (Pentair SuperFlo VS guide, p. 11). Evaporation can take the level down between top-ups, more so in an East Valley summer.
3. Check the valves. Suction valves open, return valves open. Pentair's chart asks you to make sure the suction-line valve is working and open (Pentair SuperFlo VS guide, p. 18). Diverter valves get moved and forgotten, sometimes by whoever last serviced the pool. Automated valves are covered on our valve actuator repair page.
4. Check the pump lid and o-ring. Lid seated flat and locked by hand, never with tools. O-ring clean, uncracked and sitting in its groove, and no debris on the seat around it (Jandy VS pump manual, p. 18). How to lubricate it depends on the brand: Hayward specifies "Jack's 327" (Hayward Super Pump 700 manual, p. 11), while Jandy says to use no lubricant or sealant at all — soapy water only (Jandy VS pump manual, p. 18). Follow the manual for your pump.
5. Look at the returns. Bubbles coming out of the return fittings mean air is getting in on the suction side (Hayward Super Pump 700 manual, p. 11–12).
6. Refill the pot and re-prime. With the breaker off and pressure released, fill the strainer pot with water up to the inlet, lock the lid, restore power, open the filter's air relief valve and stand clear while you start the pump. Close the air relief valve once a steady stream of water comes out (Pentair SuperFlo VS guide, p. 17; Hayward Super Pump 700 manual, p. 7).

How long priming should take

Manuals give different limits. Use the one for your pump, and stop it if it goes past that.

Pump	What the manual says
Hayward Super Pump 700 (single-speed)	May take up to ten minutes; if it hasn't primed within five, stop and find the cause (p. 7)
Hayward VS Omni pumps	Can take up to fifteen minutes; if not primed in fifteen, stop and find the cause (p. 11)
Pentair SuperFlo two-speed	Prime on high speed, and not longer than eight minutes (p. 6)
Pentair SuperFlo VS	Priming mode runs at 3450 RPM for 5 minutes by default (p. 11)
Jandy VS (H0707400 models)	Default priming speed 2750 RPM, about fifteen minutes at 10 ft above the water; at 3450 RPM, within about six (p. 18)

Variable-speed pumps

A variable-speed pump can be running exactly as programmed and still move too little water.

• Speed and schedule. Pentair lists a speed set too slow for the filtration cycle as a cause of inadequate circulation, alongside a dirty filter or pump basket and undersized piping (Pentair IntelliFlo VS+SVRS guide, p. 28).
• Priming alarms. If an IntelliFlo VS+SVRS doesn't prime within its set maximum priming time, it stops, shows a priming alarm for ten minutes and tries again; after five failed attempts the alarm stays until it is reset by hand (Pentair IntelliFlo VS+SVRS guide, p. 27). Pentair's chart also ties a pump that never leaves priming mode, or leaves it too early, to the priming range setting (p. 29).

Pentair's causes for a priming failure are on the suction side — air leaks, not enough water, a clogged basket or impeller — so work through the checks above before changing settings. Our variable-speed pump repair page covers drive settings, alarms and motor faults.

Where it stops being homeowner work

• Opening the pump to inspect or clear the impeller. It means switching off and isolating the pump and separating the motor from the housing (Pentair IntelliFlo VS+SVRS guide, p. 29). Hayward's answer to a damaged impeller is to replace it with a new seal assembly (Hayward Super Pump 700 manual, p. 12).
• A clogged suction line. Hayward's answer is to contact a qualified repair professional, and it gives 5–6 inches of vacuum at the strainer cover as the reference, measured with a vacuum gauge (Hayward Super Pump 700 manual, p. 11–12).
• A suction-side air leak that is not visible. Those are often at a fitting or underground and are found by testing rather than by looking — our equipment leak repair page covers how.
• A filter that reads normal pressure and still restricts flow, which is a real and confusing failure mode. See pool filter repair.

Why running it like this is not harmless

Water is what cools and lubricates the pump's shaft seal (Hayward Super Pump 700 manual, p. 7). Run the pump dry and the seal is damaged and starts to leak; keep running it and Pentair warns of damage to the pump body, impeller and seal (Pentair SuperFlo VS guide, p. 11). If the basket will not hold water, switch the pump off until someone can look at it.

Get it looked at

Not sure what's wrong? A $120 diagnostic finds what has failed and what fixing it involves, and the $120 is credited toward your repair if you go ahead. If you would rather narrow it down first, the Pool Problem Finder asks the questions a technician would and points you to the next step. Pool pump repair covers impellers, seals and lids, and pool equipment diagnostics explains how the visit runs.

Related

Pool filter repair · Pool pump losing prime · Pool pump repair · Variable-speed pump repair · Pool pump making a loud noise

Sources

Manufacturer documents opened and read for this page. Page numbers are the printed numbers in each document.

• Hayward Super Pump 700 Series Owner's Manual, IS26001 Rev-B — pressure warnings p. 2; start-up, priming and strainer cover p. 7; troubleshooting p. 11–12.
• Hayward VS Omni Pump Owner's Manual, 092708 Rev B — starting and priming p. 11.
• Pentair SuperFlo High Performance Pump Installation and User's Guide, P/N 350096 Rev. P (12/19/23) — high-pressure and strainer pot warnings p. 4–5; priming p. 6.
• Pentair SuperFlo VST, SuperFlo VS and SuperMax VS Installation and User's Guide, P/N 356292 Rev. A (7/10/20) — priming mode and water level p. 11; restarting p. 17; troubleshooting p. 18.
• Pentair IntelliFlo VS+SVRS and IntelliPro VS+SVRS Installation and User's Guide, P/N 356916 Rev. D (11/6/23) — alerts p. 27; troubleshooting p. 28–29.
• Jandy Variable-Speed Pumps Installation & Operation Manual, H0707400 Rev F — start-up, priming and basket cleaning p. 18.