Pool Pump Volute: Function and Maintenance

What is a volute in a pool pump?

A volute is the curved, spiral-shaped channel inside the pump housing that collects water from the spinning impeller and directs it toward the discharge port. As water exits the impeller at high speed, the volute's widening cross-section slows the water down, which increases its pressure. This pressure pushes the water through the filter and back to the pool.

In a pool pump, the volute is part of the pump body, often made of thermoplastic, composite, or metal. The impeller sits inside the volute, and the two work together to move water. The volute's shape is designed to match the impeller's output, so the pump can operate efficiently. When reading a pump listing, the volute is not usually named, but the housing material and the pump's flow rating give clues about its design.

The volute is different from the diffuser, which is a separate component in some pumps that also helps convert velocity to pressure. In many pumps, the volute is the main pressure-building element. Understanding the volute helps you know what to look for when comparing pumps and what to maintain over time. For more on pump components, see the article on pool pump impeller size.

How the volute works with the impeller

The impeller is a rotating disc with curved blades that spins inside the volute. As the impeller turns, it flings water outward by centrifugal force. The water enters the volute at high speed, and the volute's expanding shape converts that speed into pressure. This is why the volute is sometimes called a 'scroll' or 'spiral casing.'

The size and shape of the volute must match the impeller's diameter and speed. A pump with a larger impeller or a higher speed needs a volute that can handle the flow. In a listing, the impeller size and the pump's flow rate (in GPM or GPH) indicate the volute's capacity. The pump's horsepower (HP) and speed type also affect how much water the volute can process.

When comparing pumps, look at the stated flow rate and the pump's speed type. A variable speed pump can adjust its speed, which changes the water's velocity entering the volute. The volute is designed to work across the pump's speed range. For more on speed types, see the guide on variable speed pumps.

Common volute issues to watch for

The volute can develop problems over time, and knowing them helps you decide when to replace a pump or repair it. One common issue is cracking or warping, especially in pumps with thermoplastic housings exposed to extreme temperatures or physical stress. A cracked volute can leak water and reduce pump pressure.

Another issue is wear from debris. Sand, dirt, and small stones can pass through the impeller and erode the volute's inner surface. This wear can roughen the channel, reducing the pump's efficiency. A worn volute may also cause noise or vibration.

Debris buildup can also block the volute, especially if the strainer basket is not emptied regularly. A clogged volute restricts water flow, which can cause the pump to run dry or overheat. To avoid this, check the strainer basket and clean it as the maker's manual directs. For more on the strainer basket, see the article on pool pump strainer basket.

If you notice a drop in water flow or pressure, the volute may be damaged or blocked. In that case, consult the pump's manual for inspection and repair steps. For a new pump, choose a model with a durable housing material, such as reinforced thermoplastic or composite, which resists cracking.

How to care for the volute

Caring for the volute is mostly about keeping the pump clean and preventing damage. First, always keep the strainer basket free of debris. A full basket can allow debris to reach the impeller and volute, causing wear. Empty the basket regularly, following the maker's instructions.

Second, check the pump housing for cracks or leaks, especially after winter or a freeze. If you see a crack, the volute may need replacement. The maker's manual will guide you on whether the housing can be repaired or must be replaced.

Third, avoid running the pump without water, as this can damage the impeller and volute. Make sure the pump is primed before starting. Also, protect the pump from extreme weather, as freezing can crack the housing. For winter, follow the maker's winterizing steps. For more on winterizing, see the article on pool pump winterizing.

Finally, when shopping for a pump, consider the housing material and the pump's build. A pump with a sturdy volute is more likely to last. For more on pump housing materials, see the article on pool pump housing material.

What to look for in a pump listing

In a pump listing, the volute is not usually mentioned by name, but you can infer its quality from other details. Look for the housing material, such as 'thermoplastic' or 'composite.' These materials are common and resist corrosion. Some pumps list 'reinforced' or 'engineered' plastic, which indicates a stronger volute.

The pump's flow rate, stated in GPM or GPH, tells you how much water the volute can handle. A higher flow rate means the volute is designed for more capacity. Also, check the pump's horsepower and speed type. A variable speed pump may have a volute that is optimized for different speeds.

When comparing pumps, read the bullet list for features like 'corrosion-resistant housing' or 'heavy-duty construction.' These words suggest a durable volute. For more on reading pump listings, see the article on how to read a pool pump listing.

What to pick for your situation

Questions

What is the volute in a pool pump?

The volute is the spiral-shaped channel inside the pump housing that collects water from the impeller and converts its velocity into pressure, directing it to the filter.

How do you know if your volute is damaged?

Signs of a damaged volute include water leaks, reduced water flow or pressure, and unusual noise. Inspect the housing for cracks or wear, and consult the maker's manual for repair steps.

Can you repair a cracked volute?

Some cracks can be repaired with epoxy, but it's often safer to replace the housing or the pump. Follow the maker's manual for guidance, and consider a new pump if the damage is severe.

Does the volute affect pump performance?

Yes, the volute's shape and condition directly affect the pump's ability to build pressure and move water. A worn or blocked volute reduces efficiency and flow.

What materials are volutes made of?

Volutes are typically made of thermoplastic, composite, or metal. Thermoplastic and composite are common in residential pumps for corrosion resistance and durability.