Pressurized Well Water System – How it Works

I’m going to address trouble-shooting external leaks, internal leaks and pressure switch failures in well water storage systems that utilize pressurized water storage tanks, so I thought an introductory article about how the system works might properly set the stage. So, here is an overview of a basic system. This might match what you have, or it might be quite different. I drew this to be what I consider close to ideal when it comes to configuration.

Two notes on the illustration. First, I haven’t shown every feature such as pressure relief, unions, power supplies, wiring, and breaker box. These are important, but I left them out so as not to clutter up the drawing.

Second, I didn’t purposely make the drawing fuzzy so you’d have an eye test today. It just turns out that way when I insert it into the article. Here is a larger and clearer view of the diagram.

System Overview

The idea behind a pressurized well pump water supply system is to pump water out of the ground to feed house loads such as indoor appliances and faucets, and outdoor spigots and hydrants. The storage and supply portion of the system uses a tank that has a bladder, with water on the input side, and pressurized air on the other side. Think of this like a thick balloon inside of a metal tank, but instead of air inside the balloon, it’s water, and air is on the outside of the balloon, held captive by the tank. The air in the tank is compressed by the water that enters and inflates the bladder, and the force of compression allows the tank to hold and supply water under pressure.

The advantage of using pressurized storage tanks is that water can be supplied by these tanks many time throughout the day without the need for the pump to turn on. As long as there is sufficient pressurized water stored inside the tank, the pump does not operate. This saves wear on the pump, and allows the system to provide water for at least a while even in the event of a power outage – until the system drains down completely.

My system at home has multiple tanks. This requires that my pump run longer, but less often (thus enhancing system reliability), and it gives me plenty of reserve water capacity in the event of a power outage. For systems that don’t use pressurized water storage (or gravity feed), the pump turns on each time there is a demand for water. That means you’re out of water once the power goes out.

Selected Components

The system depicted above uses a pressure switch that senses water pressure in the storage tank. The switch turns on the pump when pressure goes low, and turns off the pump when pressure rises to satisfactory levels. Local gauges help show how much pressure is inside the system. These can be used to adjust the pressure switch, diagnose system problems, and determine when maintenance is necessary.

Some systems, like the one shown, have a screen and/or filter associated with them. These components help keep sand and other naturally occurring debris out of the storage tanks and out of your water supply in the house. Screens can be cleaned when they load up with particles, but filters must be replaced as they clog up with fine silt. You can select from a range of filters according to particle size that you wish to capture, and some filters offer charcoal membranes that absorb odor-causing agents in the water.

Check valves are spring-loaded one way valves that allow water to flow past them in one direction, but prevent water from flowing backwards. They keep stored water from returning to the well. A foot valve (a type of check valve) helps keep the water line from the pump filled so you don’t introduce air into the system or hammer the system with each pump start.

Isolation valves (usually gate or ball valves) help close off portions of the system for maintenance, repair and testing. During normal operations, the isolation valves are always open.

System Operation

When water pressure drops due to usage, or leaks in the system, the pressure switch makes a connection between the main power supply and the pump motor start circuit, and the pump starts running. Water flow opens the check valves (and foot valve) to allow water to be pumped from the well to the house loads and storage tank.

As water flows out of the well, particles like sand, silt and rust are screened/filtered out of the water. Fine silt will always pass through even the best filters, but particles that can damage your system will be taken out.

Pressure gauges show water pressure on the pump side of the system as well as the storage side. The difference in readings between the two indicates, in relative terms, how loaded up the screen and filter elements have become.

The pump continues to operate until the pressure tank is filled and sufficient pressure inside the system activates the pressure switch to disconnect power to the pump motor. Once flow from the pump ceases, the check valves and foot valve quickly close to keep water from flowing back into the well.

As water is drawn off of the storage tank through normal usage in the home, the bladder inside the tank keeps air pressure on the stored water, but the delivery pressure naturally drops as the water is consumed from the tank. The pressure gauge near the pressure switch will show how much pressure remains in the system as it is consumed. If no demand for water is seen, and there are no leaks in the system, it remains in a pressurized state, ready to supply water to house loads.

System Problems

If you’re a homeowner with a similar system, you face three basic problems: external leaks; internals leaks; and, pressure switch failure. These will be the topics of my next set of articles on pressurized well water storage systems.

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Clair Schwan configured his own water supply system to have adequate pressure, high capacity, and good service reliability. He knows that trouble can spring up when you least expect it, and water is something you just can’t do without. See his advice about how to save energy when using a well water system and learn about the advantages he sees in having more than one water pressure tank in a pressurized well water storage system.