The flow rate of a garden hose measures the volume of water that passes through it over time, typically expressed in gallons per minute (GPM) or gallons per hour (GPH). Understanding this flow rate directly impacts the efficiency of nearly every outdoor watering task, from filling a pool to setting up an irrigation system. This knowledge helps accurately budget water usage and determine the necessary operating time for a given task. This measurement is distinct from water pressure, which is the force exerted on the water.
Establishing the Baseline Flow Rate
The standard garden hose in a residential setting, typically one with a 5/8-inch internal diameter, delivers water within a predictable flow range. Under typical municipal water pressure (40 to 60 pounds per square inch, or PSI), the flow rate averages between 9 and 17 gallons per minute (GPM) when running freely without a restrictive nozzle. GPM is the standard measurement for hose volume, but it can be easily converted to gallons per hour.
To calculate the equivalent gallons per hour (GPH), one simply multiplies the GPM by 60. Therefore, a standard 5/8-inch hose delivering 9 GPM translates to 540 GPH, while 17 GPM equates to 1,020 GPH. These baseline figures assume the hose is fully open, has a moderate length, and is free of kinks or attachments.
Key Factors That Alter Hose Flow
The flow rate often deviates from the baseline due to several physical variables, the most significant of which is the water pressure supplied by the source. Water pressure, measured in PSI, is the force that pushes the water through the hose; a higher PSI generally results in a greater flow rate. However, the relationship is not always linear, as other factors introduce resistance.
The internal diameter of the hose plays a major role in determining the maximum volume that can pass through. A wider hose, such as a 3/4-inch diameter model, offers less friction against the water, allowing for a significantly higher flow rate compared to a narrower 1/2-inch hose. This difference means a larger diameter hose can deliver more GPM even at the same pressure.
Hose length also introduces friction loss, which reduces the flow rate over distance. As water travels along a longer hose, the constant contact with the interior walls creates resistance, diminishing the pressure and volume delivered at the end. A 100-foot hose will therefore have a lower flow rate than a 25-foot hose of the same diameter. Furthermore, the use of a spray nozzle or a sprinkler system will intentionally restrict the flow, often reducing the GPM well below the open-hose baseline to achieve a desired spray pattern or mist.
Measuring Your Actual Flow Rate
To determine the precise flow rate for a specific hose setup, the most reliable and simple method is the “bucket test.” This test requires a container of a known volume, such as a 5-gallon bucket, and a stopwatch. Begin by ensuring the hose is connected to the water source without any specialized nozzle or restriction.
The process involves turning the water on fully and timing exactly how long it takes to completely fill the bucket. Once the time in seconds is recorded, the flow rate in GPM can be calculated using a simple formula: (Bucket Volume in Gallons / Time to Fill in Seconds) × 60. For example, if a 5-gallon bucket takes 30 seconds to fill, the GPM is 10 GPM.
This GPM result can then be multiplied by 60 to find the actual GPH for that specific hose and water pressure combination. It is important to remove any fittings from the tap before starting the test to measure the true open flow of the system. This practical measurement allows for an accurate assessment of the water delivery capacity for home projects.
Practical Applications of Flow Rate Knowledge
Knowing the GPH or GPM of a garden hose transforms water usage into a measurable, controlled process. For large-volume tasks, such as filling an above-ground pool or a pond, the GPH figure allows for an accurate calculation of the total time required. A pool requiring 5,000 gallons can be timed precisely based on the known hourly flow rate of the hose being used.
The flow rate is also necessary for matching the hose output to modern irrigation equipment. Drip systems and many sprinkler heads are designed to operate optimally with a specific GPM input, and exceeding that limit can lead to inefficiency or system damage. By knowing the available flow, users can select the correct number of heads or emitters to operate simultaneously on a single line. This data is also useful for water conservation and budgeting, as the GPH figure provides a direct measurement of consumption.