Waterway makes some of the most popular pool and spa pumps on the market — the Mighty Flo, Executive, and SVL series are found in thousands of installations. When a Waterway pump won't prime, the pool sits stagnant and chemistry deteriorates fast. Most priming failures have a straightforward cause that can be found and fixed in under 20 minutes with the right approach. Here are the 6 steps to follow, in order.
Before touching the pump, walk to the pool and check the water level. If it's below the midpoint of the skimmer opening, the skimmer pulls air rather than water. This is the single most common cause of priming failure on residential pools, especially in hot weather when evaporation is high. Add water to raise the level to the midpoint of the skimmer, then re-test the pump.
The pump lid o-ring seals the basket chamber from atmospheric air. If it's cracked, dried, dirty, or not properly seated in its groove, the pump pulls air through the gap and never achieves a solid water column. Remove the lid, remove the o-ring, and inspect it carefully. A good o-ring should be:
Clean the o-ring groove, lubricate the o-ring with a silicone-based lubricant (never petroleum-based — it degrades rubber), and reinstall. Teflon-based pool o-ring lubricants like Magic Lube work well.
Carry a Waterway replacement lid o-ring kit on your service vehicle — a $3 o-ring prevents a callback. The most common Waterway pump o-ring sizes are 5-1/4" and 5-1/2" depending on model.
If the pump has lost its water column completely (common after power outages or filter backwashing), you need to manually fill it before it can self-prime:
If the basket drains immediately when the lid is removed or if priming water disappears the moment the pump starts, you have an air leak somewhere upstream.
Air infiltration on the suction side is the root cause in most persistent priming failures. With the pump running, watch the basket lid carefully for a continuous stream of bubbles — any bubble stream means air is entering. Common leak points:
Apply water from a garden hose to each suspected fitting while the pump runs. When the pump momentarily pulls in the water (you'll see the bubbles in the basket lid stop briefly), you've found your leak.
A partially clogged impeller reduces suction dramatically, preventing the pump from lifting water up the suction line. Even 25% impeller obstruction can be enough to prevent priming in a system with significant lift. Remove the pump volute (unscrew the clamp or bolts), reach into the impeller, and manually remove any debris. Spin the impeller by hand to confirm free rotation. Reassemble and test.
The diffuser (the stationary ring behind the impeller) can crack or warp. A cracked diffuser allows water to recirculate internally instead of building suction in the volute. Remove and inspect — any crack requires replacement. While you're in there, inspect the mechanical seal for signs of leakage (a water stain or mineral deposit ring around the shaft is a telltale sign). A leaking seal allows air infiltration past the motor shaft.
Warning: Never run a Waterway pump dry for more than 30–60 seconds. Mechanical seals are water-cooled and lubricated. Dry running destroys the seal face in minutes and can cause the impeller housing to crack from heat buildup.
You can use SplashLens to cross-reference Waterway pump model numbers, o-ring sizes, and seal part numbers — offline, no signal required.
SplashLens includes pump priming guides, part cross-references, and flow charts for Waterway, Pentair, Hayward, and more. Free, no login.
Open SplashLens Free →The most common causes are: low pool water level, air leak on the suction side (pump lid o-ring, unions, drain plugs), clogged impeller, closed suction valve, or loss of prime from sitting idle. Start with water level and the pump lid o-ring.
Remove the pump lid, fill the basket chamber completely with water from a hose or bucket, reinstall the lid (ensuring the o-ring is seated and lubricated), then start the pump immediately.
Yes. A partially or fully clogged impeller reduces suction so severely the pump cannot pull water up the suction line. Remove the pump volute and clear the impeller before restarting.
Yes — it's one of the most common causes of air infiltration and priming loss. The o-ring should be pliable and round in cross-section. If it's flat, cracked, or has cuts, replace it and lubricate with a silicone-based o-ring lubricant.
A Waterway pump with a full basket and good suction conditions should prime within 1–3 minutes. If it's still not primed after 5 minutes of running, there is an air leak or obstruction that must be found and fixed.