Pressure Storage Tank Guide

Pressure Storage Tank Guide

When it comes to your private water system’s pressure tank it is easy to take it for granted. However, it is important to understand what the tank’s purpose is and the way it works.

A private water system’s pressure tank has three main purposes. First, it stores water. It also supplies water under pressure whenever the pump is not functioning. It builds a reserve water supply so that when the pump doesn’t start and stop as often, it prolongs the pump’s life. It also supplies a reserve water supply to use during times of high demand.

A pressure tank’s operation is based on certain physical properties. While air can be compressed into a small area, water cannot. Whenever water is pumped inside of a tank that contains air, it compresses the air, which places the water under great pressure. The higher the amount of air that is compressed, the higher the water pressure is. Whenever the water reaches its preset pressure, which is usually 40-60 psi (per square inch), the pump shuts off automatically. As water continues to be used, the tank’s pressure is reduced. Then when the water reaches its preset pressure usually 20-40 psi, it causes the pump to start up again. The tank’s minimum pressure has to be as high at least as the amount of pressure that is needed by any appliance or fixture that uses water. To operate correctly, many require a minimum of 10 psi. Dishwasher, clothes washers, water softeners, and water treatment units might need a higher water pressure in order to function correctly; potentially up to 30 psi or even higher.

There are different kinds of pressure tanks that are available. Older pressure tank types included galvanized steel tanks that have a floating wafer and regular galvanized steel tanks. These days it is common for pressure tanks to have a rubber bladder or diaphragm.

The most common kind of pressure tank that was used by until 1970 with private water systems was the galvanized steel tank. One major disadvantage that the galvanized steel tank has is that water and air come int direct contact with one another. Some of the water may be absorbed by the air, and this air needs to be replaced so that the tank does not become waterlogged. If that occurs, there will not be much air remaining in the tank to get compressed, so almost every time that water is used the pump runs. Also, when the tank has too much air in it that causes a problem since it reduces the amount of space that is available for storing water. Extra air has to be released. Otherwise, the tank becomes air-bound. the volume of air can be controlled automatically when the steel pressure tank has an air-volume device that is attached to it. Steel galvanized tanks that have a wafer comes with a floating wafer to separate the air out of the water.

A majority of private water systems since 1970 have used a bladder-style pressure tank. Usually, the bladder is a bag that is made out of flexible polyvinyl chloride or butyl rubber. The water is held inside of the bladder and doesn’t come direly in contact with the air that is inside of the tank. The bladder that holds the water expands inside of the pressure air space as the tank continues to fill. As the system uses the water, the bladder starts to collapse until the water is nearly emptied before reaching the minimum pressure, which activates the pump. These are pressurized in the factory (usually, at about 20 psi). However, you can adjust the pressure by using the air valve that is located close to the top part of the tank. Since there is practically no water remaining inside of the bladder whenever the tank is turned on. this type of tank might not be well-suited for low-yield wells (e.g. when the pumping rate is very slow) unless an extra tank is utilized. Diaphragm pressure tanks sometimes are used as well. The diaphragm is a type of membrane that separates the air and water inside of the tank.

One way that you can choose the right pressure tank size is basing it on the flow rate of the pump. Water supply pumps typically supply water at a 5-10 gallon per minute (gpm) rate. To determine the right size of bladder tank or diaphragm, the flow rate should be multiplied by four. For example, a 36-gallon storage tank would be needed by a 9-gpm pump. The same size formula is used for galvanized steel tanks that have a wafer installed. For galvanized steel tanks that don’t have a wafer installed, they are sized at 10 times the flow rate. So, a 90-gallon storage tank would be needed by a 9-gpm pump. Consult with the pump supplier in order to determine what the right pressure tank size is for your specific water system.

There are exceptions, like with all formulas, including systems that have low-yield well. If you own a low-yield well, your pump supplier can help you figure out the right size pressure tank.

Also, motors and water pumps that are designed to be used with a variable frequency drive (VFD) motor controller are also very popular, particularly with submersible pumps. They are also referred to as constant pressure water system due to the fact that the controller determines what speed the pump motor needs in order for pressure to be maintained. Whenever water is used, the pump speeds up and the pressure drops. When the use of water stops or slows down, the pump stops or slows down and the pressure increases. This maintains almost constant pressure. For more household uses, usually, only a 1-2 gallon pressure tank is needed for a VFD-controlled water pump. Let Wells Inc., provide a well solution for you. Contact us today!

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