I often get asked the following questions about wells: This well is low-producing. How did they get a building permit? How many gallons per minute are required to obtain a building permit?
The minimum requirements to obtain a building permit in our area may surprise you. Before the county will issue a building permit, the applicant must prove that their potable water source is both safe and reliable and will provide an adequate supply for the intended use of the building. Most often, this water source is a drilled well.
To prove these things, you must first demonstrate the quantity of the water supply. This is accomplished by providing a copy of the well log or the results of a pump test. A pump test measures the quantity of water produced over a four-hour period and is usually reported in gallons per minute (GPM). In Stevens County, you must provide at least 800 gallons per day, or 0.56 gallons per minute. Spokane County requires 1,400 gallons per day, or 1 gallon per minute.
This is not a lot of water! If your well is near this minimum requirement, you may want to consider installing a water storage tank to avoid running short during periods of high household water use. The average household uses about 400 gallons of water per day, or approximately 100 gallons per person. A low-producing well may be able to supply enough water for normal household use but probably will not support watering a lawn or garden.
You must also demonstrate the quality of the water. This is done by having the water tested for contaminants at a certified laboratory. Each county has different testing requirements. Stevens County requires wells to be tested for coliform bacteria, nitrate, arsenic, lead, and uranium, while Spokane County only requires testing for coliform bacteria and nitrate.
What if your well does not meet the minimum gallons-per-minute or water quality requirements? Your project may not be dead. You may still be able to demonstrate an adequate water supply by obtaining approval to install a water storage system. If your well does not meet water quality standards, you will likely be required to install an approved water treatment system.
I consider these minimum well requirements to be quite low. Yes, you may still be able to build, but if your well is producing close to the minimum gallons per minute, you will most likely experience water supply issues in the future.