PRIVATE WATER SYSTEMS - Installation - Control Units - Centrifugal, Jet and Turbine Pumps

Centrifugal, Jet and Turbine Pumps

If any of these types of pumps are mounted in a horizontal position, then a shallow-well float-type control may be used. Pumping efficiency is greatly reduced, however. Generally, one of the following types of control is used: Diaphragm-type air control; Water-displacement control; or the

Diaphragm-type Air Controls (2)

Diaphragm-type Air controls As the pump starts, water is removed from the right side of the control by pump suction causing a partial vacuum. This causes the diaphragm to move to the right against a spring. The sudden action causes a partial vacuum to form in the control on the left side of the diaphragm if the water in the pressure tank is above the opening connecting the tank. At the same time the partial vacuum causes outside air to force open the sniffer valve, and a charge of air enters the control.

When the pump stops, all the suction is removed from the diaphragm, and the spring forces the diaphragm to the left. This action forces the new charge of air through the small opening into the tank.

If the water level in the tank is below the water control, then air moves form the tank into the control instead of from the snifter valve. When the pump stops, the air is then forced back into the tank, no new air is added.

This type of control must be matched with the tank size. Also, the pump must turn on and off frequently, because air is added or re-moved only at the beginning or end of each pumping cycle.

Water-displacement Controls (2)

Water-displacement Controls When the pump starts, there is an immediate difference in pressure between the point where the control connects to the pressure tank and the point where the suction tube connects to the pump suction line. The highest pressure is at the tank connection. If the water level in the tank is above the opening to the control, water from the tank passes through the jet into the air-control cylinder. As a result, suction develops at the snifter valve, and air is carried with the water into the air-control cylinder until the air-control float valve seats in the charger. This stops further water removal from the cylinder.

When the pump stops, the water pressure equalizes amongst the pressure tank, the pump, and the pump suction line. Water moves from the pump suction line back into the air-control cylinder. The air- control float valve is lifted, and the cylinder fills with water. The new charge of air from the air-control cylinder is forced into the tank.


Displace If, when the pump starts, the water level is below the tank connection to the control, air flows into the cylinder from the tank. The air movement from the tank into the cylinder does not develop enough suction to open the snifter valve. As a result, no new air is added to the tank. Other designs for the same operating principle can be found in.


Venturi-and-Air-Release Controls (2) (2)

Venturi-and-Air-Release Controls The venturi unit is placed between the pump and the pressure tank. The pressure-drop adjuster valve is closed enough to force some water through the venturi as it passes from the pump to the pressure tank. Water passing through the venturi causes a partial vacuum at the snifter valve. This partial vacuum is enough to draw water into the water line and into the pressure tank.

When too much air accumulates for proper tank operation, the air is released through an air-release mechanism shown in the figure. This type of control may be used with ant of the centrifugal or turbine pumps.

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