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Pressure Tanks – What You Need to Know

Davey pressure tanks

Technology of the modern pump coupled with the way we use water in homes, means we no longer install a new pump without a pressure tank. The home appliances used these days put higher demand on home pressure systems than they did twenty years ago, and pumps themselves are no longer manufactured the same way – they are still robust but have some components which are now made of plastic.

A pressure tank keeps your pump from turning on and off every time there is a demand for water. It also provides dampening protection from water hammer generated by household appliances. Your pump’s warranty doesn’t include damage caused by water hammer so it’s an important piece of equipment in your home pressure system.

What is water hammer?

Water hammer acts like a shock wave travelling back down the delivery line which depending on its strength and/or frequency can either split the casing or cause at least two or more of the casing bolts to shear off.

Water hammer can be generated from any device which is fitted with a quick acting solenoid valve and includes common household appliances such as mixer taps, dishwashers and high-pressure hot water cylinders. Water hammer is the “clunk” you hear when the mixer tap is turned off quickly. Most high-pressure hot water systems discharge pressure after an extended period of no demand, which is normally the middle of the night, so the resulting water hammer is often not heard or observed by the home owner.

In order to remove the potential for water hammer damage on the pump we recommend a pressure tank be placed in the delivery line*. Once installed the pressure tank will act as a “buffer” which will dissipate any water hammer which may occur. The pressure tank should be a minimum of eight litres in capacity to ensure an adequate buffer is created.

*If the pump is fitted with a Torrium2 controller then the pressure tank should be at least 1 meter from the pump to ensure the features of the Torrium2 controller are not affected by the pressure tank.

How does a pressure tank work?

Water cannot be compressed into a smaller area, while air can. When water is pumped into a tank containing air, the air is compressed, putting the water under pressure. The more the air is compressed, the greater the water pressure. When the water reaches a pre-set pressure, the pump automatically shuts off. As water is used, the pressure in the tank is lowered. When the water reaches a pre-set pressure, the pump starts again. The minimum tank pressure must be at least as high as the pressure needed by any water-using fixture or appliance.

Traditionally a pressure tank would sit on top of a pump, but this causes unnecessary weight on the pump so is no longer best practice. We install the pressure tank 1m from the pump to ensure electronic controllers of the pump are not interfered with.

Selecting the correct size for a pressure tank is usually determined by the type of pump you have and the pump’s flow rate along with your water source. Our team can help you determine the best pressure tank for your home pressure system.