Gallatin Valley Water Well Flow Rate & Capacity Information

by Craig Delger

Given the drought that is impacting many western states, one of the most common questions clients ask is about the well on a property, how much water is in a well, and is it adequate for the average home.

When buying land or a house with a private well, well flow rate, well yield, and water quantity are important factors.

The ground water resources for the Bozeman area are controlled by the Gallatin Local Water Quality District(GLWQD).

For real estate in Gallatin Valley the most common well water measurement is flow rate, typically described as Gallons Per Minute. The Federal Housing Administration (FHA) requires 3 to 5 gallons per minute for older wells and a rate of 5 gallons per minute for new wells to pass inspection.
The average American household needs 100 to 120 gallons per person per day, and a flow rate of about 6 to 12 gallons per minute. This requirement may be higher if the well serves a home housing a large family or there are large water demands for a large lawn or garden.

Gallatin Valley is fortunate in that most areas have highly productive wells. Private residential wells typically exceed 15 gallons per minute, and can go above 30 gallons per minute. Water capacity is another consideration. There are a few different ways to look at the amount of water in the well. The first is water storage capacity. A standard 6-inch diameter drilled well can store 1.5 gallons of water per foot. If you know the depth of the well, the level of the water and pump depth, you can figure out the water storage capacity. Most people don’t know all of this information, but it can be figured out by consulting with a water system professional.

Minimum water supply capacity for use inside a home should be at least 600 gallons within a two-hour period, or about 5 gallons per minute for 2 hours. Some homeowners may find this recommended amount to be less than they ultimately need depending on the size of the family or if there are large outdoor water demands. This is also something you can discuss with a water system professional.

What can be done if a well falls short?

If after conducting a flow rate test, the well does not meet the recommended standards, there are some options to increasing flow. If there is space on the property, another well can be dug. This is costly, time consuming and may not get the results the homeowner needs. Existing wells can be improved by a process called hydrofracking, which blasts water into an existing well bore to clear debris and open fissures allowing water to flow through the bedrock.

Hydrofracking does not use chemicals and is different from the hydraulic fracking associated with the oil and gas industry.

In addition, if a well produces below the flow rate that your family requires, a holding tank(typically 500 gallons) can be installed with proper controls on the well to keep it from pumping dry. The holding tank will provide the amount of water a family needs during peak usage periods(running dishwasher, sprinklers, and a shower at the same time). This usually is sufficient to support a family.

The last consideration is water quality. When purchasing or maintaining a property with a private water well, it is a good idea to get the water quality tested. This can reveal any contaminants that are a health risk, and also water contaminants that are not a health threat but which are aesthetic or even functional concerns such as color, sediment, water hardness, or water odors.

Much of the ground water in the GLWQD is considered hard because it contains a high proportion of calcium and magnesium. The hardness of water is expressed as a percentage of calcium carbonate, which is the principle constituent of limestone. Water is considered soft if it contains 0 to 60 mg/L of hardness, moderately hard if it contains from 61 to 120 mg/L, hard between 121 to 180 mg/L of hardness, and very hard if more than 180 mg/L of hardness. Hardness of ground water of the GLWQD ranges between 6 to 340 mg/L.