A common problem with private water systems is the loss of water pressure, generally during times of heavy use. There are a number of possible reasons for this. You might need a larger pressure tank or it could be that your pump is undersized for the amount of water needed. Your pump and your pressure tank work together to provide your water, and understanding how they work will help you determine the best solution.

Typical private well water systems that have a constant rate pump are designed to work between two pressure ranges. When you turn on a tap, it is initially supplied by the water in the pressure tank. As the tanks drains, the pressure in the tank and system decreases, which lowers the pressure level at the tap. This continues until the system reaches a preset lower pressure at which point a switch kicks on at your pump. This is the cut-in pressure.

The pump supplies water to your home, refills the pressure tank, and increases pressure in your system until the system reaches a preset high pressure at which point a switch is flipped and shuts the pump off. This is the cut-off pressure.

Most systems operate with about 20 PSI between the cut-in and cut-off pressure. For example, they may be set at 40 and 60 PSI or 30 and 50 PSI, so your home system typically has a drop in pressure of 20 PSI as water is used.

When there is heavy water use, the pressure tank may not have enough volume to supply the needed water and will eventually need help from the pump to keep up. When the water use stops, the pump will continue to run, filling the pressure tank, and increasing the pressure in the system until the cut-off pressure is reached. The larger the tank, the more water can be stored with sufficient pressure.

If this is your situation, increasing the size of your tank or adding a second tank will provide more water at a higher pressure, before relying on the pump to help keep up. If the pump is undersized and cannot provide water equal to what is being used, the pressure will continue to decrease as long as water use continues. If this were to occur, it is likely you would need a larger pump to provide sufficient water pressure.

Another solution, and one that is becoming more commonplace, is a variable speed pump. They can run at different speeds to supply a variable rate of water depending on the amount of water being used. The pump speed is managed by a control that monitors pressure and helps maintain a constant pressure in the system using the pump instead of relying on water coming from the pressure tank.

In these systems, the pressure tank is very small, maybe only a few gallons, and the pump comes on almost as soon as the tap is opened. Though the pump may run more often, these systems are much more efficient because they are not always running at maximum capacity.

The biggest advantage is the pump can speed up or slow down based on use to maintain a nearly constant pressure in the system. These pumps are a good solution as long as the well has the capacity to provide a high volume of water. They are not recommended for a low-yielding well that cannot sustain a high flow rate that meets the high demand for the system.

The Private Well Class is a collaboration between the Rural Community Assistance Partnership and the University of Illinois through the Illinois State Water Survey and the Illinois Water Resource Center, and funded by the United States Environmental Protection Agency. The views expressed here are solely from the class authors and not endorsed or reviewed by USEPA.