Whether you're replacing an old pump or installing a new water well, you'll need to determine an appropriate capacity to ensure you meet your household's typical water demands. A pump with a flow capacity that's too low will struggle to fill your pressure tank under heavy loads. On the other hand, a pump with too much power will cost more than necessary and may use excessive energy.
Your plumber will work with you to select an appropriately sized pump, but you may still want to know how to calculate your water demand on your own. In most cases, you'll make this estimation based on the number of fixtures and appliances in your home. Taking the time to perform this calculation is the best way to ensure your new pump can operate efficiently.
How Does Flow Rate Affect Your Pump's Operation?
Before you begin to calculate the necessary capacity (or flow rate) for your pump, you should understand how it impacts your well system's overall operation. Most residential wells use a tank to store water and provide pressure for the fixtures in the home. Your pump will fill this tank to a maximum preset capacity and then allow the tank to empty until it reaches a preset minimum.
Under periods of high demand, you may use water faster than the pump can reach the tank's upper limit. If the increased demand lasts for long enough, you may lose significant water pressure at your fixtures as the tank falls below its minimum set level. As a result, your pump's flow rate must be high enough to keep the tank filled at peak demand.
Calculating Your Required Flow Rate
To determine your home's total required flow rate, you'll need to take an inventory of all the fixtures and appliances in your home. It's a good idea to consider even those fixtures that you may infrequently use, such as basement sinks or bathrooms in guestrooms. The age of your plumbing fixtures matters for this calculation, and you can use a flow rate table to get some rough estimates.
Add up the total gallons per minute for your fixtures and appliances, and you'll know your peak demand. For washing machines and similar devices, you can divide the total gallons for one load by the length of a cycle in minutes. When purchasing a pump, you'll want to choose one with a flow rate that closely matches your peak demand.
Remember to consult with your plumber before making any final decisions. Well pump contractors can double-check your numbers and ensure that you aren't choosing a pump under or oversized for your needs.