Pool Pump Check Valve: Do You Need One?

What is a check valve?

A check valve is a simple mechanical device that allows water to flow through it in one direction only. It has a flap, ball, or disc that opens when water pushes in the correct direction and closes when water tries to flow backward. In a pool pump system, a check valve is typically installed in the plumbing line to prevent water from draining back into the pool or spa when the pump is off.

The term 'check valve' appears in pool equipment listings and manuals. It is not a pump component itself but a separate fitting that can be added to the piping. The purpose is to maintain water in the line, which can help the pump stay primed and reduce the chance of air entering the system when the pump starts again. For more on pump priming, see how self-priming pumps work.

When might you need a check valve?

A check valve is often recommended when there is equipment that could be damaged by water flowing backward, or when the pump is located above the water level. For example, if you have a pool heater, a check valve is commonly installed between the heater and the pump to prevent hot water from flowing back into the pump when it shuts off. This can help protect the heater's heat exchanger from thermal shock.

Similarly, if you have a solar heating system, a check valve prevents water from draining back up to the roof panels when the pump stops. This keeps the panels full of water and avoids air locks. In above ground pools, a check valve can be used on the suction line to help the pump retain its prime, especially if the pump is not self-priming.

The need for a check valve depends on your specific plumbing layout. If your pump is below the water level (common for inground pools), gravity keeps water in the line, and a check valve may not be necessary. If your pump is above the water level (common for above ground pools), a check valve on the suction line can help maintain prime. For more on pump placement, see above ground pool pumps.

Types of check valves

There are several types of check valves used in pool systems, each with a different internal mechanism. The most common are swing check valves, which have a hinged flap, and spring-loaded check valves, which use a spring to close the valve. Spring-loaded valves are often preferred because they can be installed in any orientation and close more quickly, reducing water hammer.

Another type is the ball check valve, which uses a ball that seats against an opening. These are less common in pool plumbing but may be found in some applications. When reading a listing, you might see terms like 'swing check valve' or 'spring check valve.' The choice between them often comes down to the flow rate and the vertical or horizontal orientation of the pipe. For more on flow considerations, see pool pump flow rate.

How to decide if you need one

To decide if you need a check valve, look at your pool equipment and the layout. If you have a heater, solar panels, or a water feature that is elevated, a check valve is likely a good idea. If your pump is above the water level and you have trouble with it losing prime, a check valve on the suction line can help.

Also consider if you have multiple pumps or a spa with a waterfall. A check valve can prevent water from flowing from one body of water to another when the pump is off. The best approach is to consult the installation manual for your specific pump and equipment, as makers often specify where check valves are required. If you are unsure, ask a pool professional to evaluate your setup.

Remember, this article cannot advise on specific installations. The decision depends on your pool's design, and a licensed pool installer can provide guidance based on your equipment and local conditions. For more on choosing a pump, see variable speed pool pumps.

Check valve vs. other valves

A check valve is different from a gate valve or ball valve, which are used to manually start or stop water flow. Check valves operate automatically, without any handle or control. They are also different from a diverter valve, which directs water to different parts of the system.

In a pump system, you might see a combination of valves. For example, a check valve might be installed near the pump discharge to prevent backflow, while a gate valve is used for maintenance isolation. Understanding the role of each valve helps you read a plumbing diagram and know what your system needs. For more on pump components, see pump strainer baskets.

What to pick for your situation

Questions

What does a check valve do in a pool pump system?

A check valve allows water to flow in only one direction. In a pool pump system, it prevents water from flowing backward when the pump is off, which can help maintain prime and protect equipment like heaters or solar panels.

Do all pool pumps need a check valve?

No, not all pool pumps need a check valve. It depends on the pump's location relative to the water level and whether there is equipment that could be affected by backflow. For example, inground pumps below water level may not need one, while above ground pumps may benefit.

Can a check valve help your pump stay primed?

Yes, a check valve on the suction line can help an above ground pump retain water and stay primed, especially if the pump is not self-priming. It prevents water from draining back into the pool when the pump stops.

Where is a check valve typically installed?

A check valve is usually installed in the plumbing line, either on the suction side (before the pump) or the discharge side (after the pump). The exact location depends on the purpose, such as protecting a heater or solar panels.

Is a check valve the same as a backflow preventer?

No, a backflow preventer is a more complex device used to protect drinking water supplies, while a check valve is a simple one-way valve for pool plumbing. They serve different purposes and are not interchangeable.