Well Pump Check Valve
Figure 1: Check valve
Check valves are an essential component of well pump plumbing systems. They stop water from flowing back into the well when the pump turns off, protecting the system from various problems. Whether a well's plumbing system needs one or multiple check valves depends mainly on the depth of the well. This article looks closely at well pump check valves to help users understand their function and how to use them effectively in a well's plumbing system.
Table of contents
- Check valves and their function
- Well pump check valves
- Why well pump check valves are important
- Well pump check valve installation and maintenance
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Check valves and their function
Before diving deeper into well pump check valves, it is helpful first to understand what check valves are and how they work. Check valves are the simplest directional control valves. Their function is to allow flow to move in one direction and prevent flow from moving in the opposite direction. A check valve opens when media flows through it and closes when the media stops flowing or if backflow occurs. For a comprehensive understanding of check valves, read our check valve article!
Well pump check valves
The spring-assisted check valve (Figure 2) is the correct valve for a well pump's plumbing system. When the pump operates, the pressure of the water flowing into the valve opens it. When the pump shuts off, the spring and backflow pressure combine to close the valve quickly. This rapid closure is essential for diminishing water hammer in the system. Swing check valves are unsuitable because they close too slowly for a well pump application.
Figure 2: Spring-assisted check valve: flow direction (A), o-ring (B), poppet (C), and spring (D).
Why well pump check valves are important
A regularly operated well pump needs to stay primed, which means that when it’s not running, it needs to be able to turn on and function normally. Most well pumps need water within the pump and piping to work. Without a check valve, water would flow out of the pump and back into the well when it shuts off. The pump would be empty of water and unable to work without a user manually priming the pump.
Not having a primed pump is not the only concern if water freely flows back into the well. Check valves also protect pumps from backspin, water hammer, and upthrust, all of which can cause damage to the motor or piping.
- Backspin: When water freely flows back into a well, the pump may spin in the reverse direction. If the pump turns on during a period of backspin, the force put on the motor to reverse the pump direction can break the pump.
- Water hammer: A failed or leaking check valve can cause a vacuum to form in the piping due to pressure in the piping being lower than atmospheric pressure. When the pump turns back on, water will fill the space at high velocity and slam into stationary water above it. The resulting hydraulic shock can damage the piping, pipe, or motor.
- Upthrust: Without a check valve, the pump starts with zero head pressure. Head pressure is the amount of pressure needed to move media from A to B. The impellers in the pump rise slightly and wear against the diffusers, which will lead to relatively quick failure of the pump and motor.
Well pump check valve installation and maintenance
Consider the following when determining which check valve to select for a well's plumbing system. The recommendation is to communicate with the manufacturer to determine if their check valves can perform adequately in the system.
- Pipe flow velocity: For the best service life in most check valves, flow velocity should not exceed 3 m/s.
- System pressure: Calculate the hydraulics of the entire system, not just the pump’s pressure setting, when determining which check valve to install.
- Before installing: Ensure that the check valve has no defects and that its spring-assisted poppet can move freely.
- During installation: The arrow on the outside of the valve’s body should face the intended flow direction when the pump operates.
Where to install well pump check valves
Figure 3: A submersible well pump system: pump (A), check valve (B) is installed at the pump’s discharge head. Check valves (C and D) are separated by at most 200 feet. Check valve (E) is installed above ground level (F).
Three types of well pumps use check valves in a plumbing system: a submersible pump, a centrifugal pump, and a jet pump. Each type of pump system will use check valves differently. The depth of the well is the primary controlling factor determining the number of check valves to use.
- Deep wells: A submersible well pump is necessary for wells deeper than about 120 feet. As seen in figure 3, the pump sits directly in the well water. Typically, the pump has a check valve installed within its body and the next check valve in line should be no further than 25 feet from the pump. If a check valve is not installed in the pump’s body, though, the first check valve should be installed at the pump’s discharge head. In both cases, the usual recommendation is to install a check valve after every 200 feet of pipe.
- Shallow wells: Submersible pumps can be used in shallow wells, but jet and centrifugal pumps work as well. Both types of pumps use a foot valve. This is a specific check valve placed directly into the water. It has a filter around its inlet port, stopping larger sediment from entering the valve and possibly sticking it open.
- Above ground: Whether or not to install a check valve outside of the well casing or above ground (e.g., before the intake of the pressure tank) depends entirely on the local law. Some legal jurisdictions require installing a check valve before the pressure tank. Other jurisdictions forbid it altogether. However, one important concept to consider is that every extra check valve in a system adds static friction to the system. When added together, the static pressure can reduce the water pressure below desired limits.
Testing a well pump check valve
A common issue in well pump systems is the pressure tank losing pressure while the pump is not operating. This pressure loss can cost a significant amount of extra money because the loss of pressure causes the well pump to cycle more frequently, which demands more power. Therefore, it’s important to figure out if a leaky check valve is a reason this pressure loss is occurring.
To test whether or not the check valve is functioning correctly, first turn off the connection between the pressure tank and what it services (e.g., household plumbing). After waiting about one hour, if the tank is still losing pressure, it means something on the downwell side of the system is the cause. In many instances, the check valve is responsible for this pressure loss and must be repaired or replaced. However, further investigation may be necessary. Breakage in the drop pipe or buried pipes running from the well to the pressure tank can also result in pressure loss in the system.
Replacing a well pump check valve
When a submersible pump’s built-in check valve goes bad, it must be replaced. After lifting the pump out of the well, the check valve can be removed and replaced. The check valve chosen to replace the broken check valve must be the same model. Replacing the check valve in the pump is an excellent opportunity to replace the o-ring around the check valve’s seal. Contact the pump’s manufacturer if you have any further questions about this.
- Stainless steel: Stainless steel check valves are not vulnerable to rust or corrosion. If the well has steel piping, the stainless steel check valves might outlive the piping.
- Ductile iron: Ductile iron check valves are a cost-effective and stronger choice than bronze check valves. These valves may be a good choice for very deep wells that use many check valves in the piping.
- Bronze: Bronze check valves are not as strong as ductile iron but are corrosion resistant.
- PVC: A PVC check valve has more chemical resistance along its surface than a bronze check valve and is significantly less expensive. However, PVC has lower mechanical strength and does not operate well under high-temperature or pressure conditions as bronze.
Typically, the poppet and spring are stainless steel. Read our chemical resistance guide to learn more about these materials' properties.
Where is a well pump located?
In submersible well pump systems, the pump is down the well, sitting in the water. In jet and centrifugal well pump systems, the pump is aboveground.
Does a well pump need a check valve?
At the very least, a well pump needs a foot valve (a special kind of check valve) that sits in the water inside the well. A check valve stops water from flowing back into the well, which keeps the pump primed and the pressure tank pressurized.