How often should you check the air pre-charge in a pressure tank (hydrophore)?

The short answer

Check the air pressure in the tank once a year. Both manufacturers read for this guide say so: Grundfos calls an annual pre-charge check essential for its SCALA2 booster, and the Flotec (Pentair) owner's manual says to check the tank air charge annually to prevent waterlogging. The check must be done with the pump off and no water pressure in the system, and the target pressure comes from your pump or tank manual.

Why the air pressure drops

A pressure tank holds air on one side of a membrane or bladder and water on the other. Grundfos explains that each pump start and stop flexes the membrane, which lets air escape and lowers the pressure over time. Low pre-charge can cause noisy operation, fluctuating pressure, a higher risk of damage and higher energy use (Grundfos). Flotec warns that losing air can lead to a waterlogged tank and bladder failure.

What the right pressure is

It depends on the system, so read the plate or manual rather than copying a number.

• Grundfos SCALA2: set the pre-charge to 70% of the pressure setpoint and never above it. As shipped it has a 1.8 bar (26 psi) pre-charge and a 3 bar (44 psi) default setpoint, so the pre-charge must be adjusted at installation.
• Flotec pre-charged tanks: the pre-charge is set from a chart according to the pressure switch setting, and the chart value is a little below the pump-on pressure. The tanks ship at 40 psi, which is only a starting point.

Those two rules differ, which is the point: use the figure for your own equipment.

How to check it

1. Switch off power to the pump (or press STOP on the unit).
2. Close the supply pipe and open a tap near the tank to drain the water side and release the pressure. Flotec says to set or check pre-charge with no water in the tank and no water pressure in the system.
3. Remove the cap from the air valve on the tank and measure with a tyre gauge.
4. If the figure is off, add or release air to reach the value in your manual.
5. Flotec suggests brushing soapy water on the valve: continuous bubbling means a leak, and the valve core can be replaced with a standard tubeless-tyre one.
6. Refit and tighten the valve cap, reopen the supply and restart the pump.

Flotec also suggests checking sooner if the usable water per cycle drops noticeably.

Before you rely on this

This reflects two manufacturers' published instructions for their own products. Grundfos's page applies specifically to the SCALA2 integrated tank, and the Flotec manual is a North American document in psi. Brands such as Lowara, DAB and Pentax were not read for this guide. Your model's manual wins, and if you are not comfortable working on a pressurised system, ask an installer.

Track it in Epimeleia

Add your pressure system as an item, attach its manual, and set a yearly reminder for the pre-charge check, with the target pressure in the notes so you do not have to look it up each time.