Pumping system components

Pumping water efficiently requires selecting and installing appropriate components. The pump should be selected based on the power supply available at the site and the required water flow. Pumping components are installed to control the flow rate and pressure under varying conditions.

An inexpensive centrifugal pump that runs continuously will avoid the frequent stop/start cycles that can cause greater pump wear and failure. With no pressure control components, a float (water-level control device) or shutoff valve at each drinking point controls the water level. A centrifugal pump continues to run even after the float or valve shuts off, so pressure is maintained for rapid water availability (Figure 1).

A pressure switch allows a pump to temporarily shut off while maintaining water pressure within a predetermined range, generally a range of about 20 pounds per square inch, and then restarts the pump when the water pressure drops below the range. Water pressure in the system fluctuates between pumping cycles but stays within the desired range. The pressure switch is generally installed on a separate tee in the water pipeline near the pump and power supply or near where the water enters the pressure tank, if a tank is used.

A pressure tank plumbed into the pressurized side of the water line reduces the number of times the pump cycles on and off while maintaining adequate water pressure. The pressure tank is a sealed vessel containing a volume of air, often in an air bladder that compresses and expands as pressurized water from the pump enters and leaves the container.

The pressure switch is set to the desired range. The air bladder is then filled with pressurized air when the tank is empty. The pressure should be 3 pounds per square inch lower than the lowest pressure of the water pressure switch range.

When the water pressure in the system reaches the high end of the range, the pressure switch turns off the pump (cut-out). When water drains from the system into a waterer, the air bladder expands as the water leaves the tank and water pressure decreases. When the water pressure drops to the low end of range, the pressure switch turns the pump back on (cut-in) to repressurize the system with additional water. The expansion and contraction of the air bladder keeps the water pressure within an acceptable range for a longer period of time while the pump is off compared to just using a pressure switch.

Leaks will lower water pressure more rapidly and result in more frequent pump cycling. The larger the tank, the greater the volume of water that can be pressurized.

A pressure gauge does not perform any water pressure control actions but is an important aid in evaluating water system performance. The pressure gauge displays the water pressure in the system and can verify that the pressure is being maintained within the desired range.

A low water sensor prevents damage to the pump when the well water level is below the pump intake level. When the water level is too low, the sensor shuts off the pump through wiring to the pump control box, which is designed to allow time for the well water level to recover before restarting the pump.

Check values and foot valves only allow water to flow in one direction through a pipeline. A foot valve is installed on the intake end of a watering system before the water enters the pump, while a check valve is installed on the pressurized side of the system. Foot valves are normally used to continuously maintain prime for the pump.

Water-level control valves (float valves) automatically maintain the water level in a livestock waterer or storage tank. Major types of these valves are diaphragm and mechanical (level-operated). The “Water-Level Control Valves” section of this handbook includes more details about these valves.

A water pressure reducer or pressure reducing valve lowers pipeline water pressure to a safe level and is most often used when the incoming water pressure is greater than 90 pounds per square inch, which is common in rural water district pipelines. A high water pressure is needed in the public water supply lines to maintain sufficient water delivery pressure for the most distant patrons. Many mechanical or lever action water-level control valves in livestock waterers fail to completely shut off when water pressures are extremely high. In some cases, the float may be nearly or completely submersed in the water and still not completely shut off water flow when the pressure is too high.

An air relief valve is placed in a pressurized water system at locations where air accumulates in the pipeline and water flow is reduced at the higher elevation points in the pipeline. Air relief valves are most often needed with longer and more complex pipeline systems. The air release valve is periodically opened to release trapped air. A livestock waterer placed at the highest elevation on a pipeline releases any trapped air without the need for a relief valve.

Shutoff valves are installed throughout a water pipeline system. Shutoff valves should be located on each branch of an extensive watering system so individual parts of the system can be isolated for maintenance and repair without shutting off water to the rest of the system, thus maintaining livestock water availability elsewhere in the pasture.

Shutoff valves are generally situated upstream of waterers and hydrants and preferably downstream of the pressure tank but before the pipeline branches out of the pump house, allowing pump components to be tested before releasing water to the entire system.

There are many styles of pipeline shutoff valves. The pipeline material often dictates the type of shutoff valve needed.

Stop-and-waste valves are used where a pipeline branch needs to be drained when not in use to prevent freezing. Often stop-and-waste valves are used for waterers or sections of the pipeline that are only used seasonally. Stop-and-waste valves have two openings: one that controls the flow of water (stop) and one that allows water to drain from that branch of the pipeline (waste).

Ball valves (or quarter turn valves) contain an internal ball with a hole through it. Turning the valve handle rotates the ball hole. Water goes through the valve when the hole lines up with the flow of water. When the hole is turned away from the flow of water, the flow rate is reduced and finally stopped.

Gate valves operate by sliding a retractable guillotine-type piece of metal (gate) across the flow of water to regulate water flow. The gate is attached to a threaded shaft extending from the middle of the valve and often ending in a circular handle.

Globe valves are constructed with a washer that fits into a seat inside the valve. The washer is attached to a threaded shaft with a circular handle at the end. Turning the handle moves the washer off or onto the seat. Water flow is regulated by the distance between the washer and the seat.

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