The Role of a Well Water Pressure Tank

Under residential applications a water well pressure tank is used to control the systems pressure. Water, unlike air, cannot be squeezed or compressed into a smaller volume. A pressure tank has air that is compressed by the rising water level in the tank as a means for storing energy. The compressed air resides at the top of the pressure tank and acts like a coiled spring.  This in turn pushes down on the water at the bottom of the tank. When a fixture or faucet in the system is opened, the air pressure at the top of the tank forces the water to flow out of the tank (drawdown) and into the system delivering water to the fixtures calling for it. The pressure in the tank will then drop below the 40/ 60 or 30/50 psi* the system is set for and the pump will kick on to provide the system with continued water flow. The pump continues to deliver water under the pressure of the tank. As the tank refills, the air over the water is being compressed readying itself for the next call for water. If no water is being used then water will continue to enter the tank until the appropriate proportion of water is in the tank. When the call for water ceases, the pressure switch will kick off and the pump then stops.

Issues Caused by Pressure Tank Problems

If you pressure tank is not working properly, it will result in water pressure issues. It will cause increased wear and tear on your well pump due to short cycling. This is caused when the well pump is turing on and off to often, most well pumps need to run for at least a minute and a half to cool after starting. It is better if your well pump runs for long periods of time, but does not start and stop often. And of course, if this is all going on your PG&E bill will reflect it. 

Well Tank Sizing

In some cases the well pump size has been changed, or inproperly sized for the pressure system and this will cause issues. Pressure tanks are not a one size fits all item. If they are not sized correctly, they will act like a bad tank. The basic idea for sizing a pressure tank is to make sure the well pump takes more than 1.5 mintues to fill the tank. In general it is better for the pump to run longer and start less often. This helps to keep the pump cool, reduce torque on the drop pipe and reduce wear on overall well components. 

Pressure tanks are set up to be 2/3 air and 1/3 water. For example: You have a 22 gallon tank which means the actual holding capacity (in terms of water) would be 7.3 gallons. This (in the event of power loss) does not give you a lot of water to work with. Most typical residential applications call for a minimum of a 50 gallon tank (slightly larger for larger homes).

Troubleshooting Tank Issues

Troubleshooting tank issues can be fairly easy for the typical handy man homeowner. It’s always good to remember the (2/1 ration 2/3 air 1/3 water) the top 2/3 of the tank should sound hollow when tapped with knuckles on the side of the tank. If this is not the case than calling for service would be recommended.

*PSI stands for pounds per square inch of pressure


Common signs your pressure system is not working correctly. 

  • Low Water Pressure
  • Rapid Change in Water Pressure
  • Well Pump Starting and Stopping Often
  • Air in your water from a failed pressure tank
  • Leaks from the pressure tank

If you have any of these issues or if you want to have your pressure system checked out, Call Silverthorn Pump TODAY! 530-520-8270








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