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Highest allowed shower head flow rate per state and cities 2022

Updated: Sep 20



We summarized the highest flow rate allowed gallon per mins (GPM) for showers in the United States in 2022 with the granularity to the city level. Here you can find out what is the highest possible flow rate you can get from shower heads in your area. Later part of this article we will share how you can enjoy the highest GPM of shower yet save more water automatically, effortlessly with Oasense Reva smart shower head. If you are thinking about remodeling bathroom or getting a new shower head, the Oasense Reva is worth your consideration, don't settle for low flow shower head if you are looking for saving water.


Also read:

How do I get the highest pressure shower and still save water?

Smart shower heads and the secret behind their functionalities.

Why low flow shower head isn't saving you water


What is GPM, gallons per minute


Standard way to describe how many gallons of water comes out of a shower head is GPM, which stands for gallons per minute. The meaning of GPM is self explanatory, how much water comes out of the shower head or the faucet per minute. The shower head flow rate in the US is measured at an 80 psi in-coming pressure so it can be compared across different test setup. 1 GPM rating means that there is 1 gallon of water coming out of the shower head every minute when water pressure is at 80 psi. 1.8 GPM means 1.8 gallons of water and so on.


Typical household water pressure in the US is between 50 psi~ 80 psi, therefore often times the actual flow rate out of the shower head would be less than the flow rate rating because they are rated at 80 psi and your house setting is likely not.


Easiest way to measure flow rate is to get a bucket to collect water coming out of the shower head, however, if you want to compare different shower heads make sure you calibrate for incoming water pressure. Time it for 1 min and measure the volume or weight of the water that is collected. A flow meter can also be used but it often needs to be calibrated to have an accurate result. You can also get a pressure gauge to measure your water pressure from the shower arm. Just remember, if you want to compare different shower head pressure rating, they should be measured at a fixed in-coming pressure, like 80 psi.


National standard - 2.5 gpm


National standard of maximum 2.5 gpm flow rate for shower heads was established through the Energy Policy Act (EPAct) of 1992 in order to save water. If the state, county or city of residency does not specify a maximum flow rates for shower heads, a 2.5 gpm shower head is the maximum one can get. This includes all type of shower heads like hand-held shower, wall mount shower head, shower head systems, and rain showers. For shower heads made pre 1990s, it is still possible to find 3.5 gpm flow rate or even higher. So hold the thought for a 5 gpm one, it's probably not available in stores.


WaterSense Certification


Another shower head flow rate limit that could be required by local governments is a certification called WaterSense. WaterSense is a voluntary program run by EPA to help conserve water across kitchen and bath. WaterSense collaborated with the American Society of Mechanical Engineers (ASME)/Canadian Standards Association (CSA) Joint Harmonization and established the first universally accepted criteria for measuring shower head performance.


The requirements address flow rates across a range of pressures, spray force, and spray coverage, the three key attributes of shower head performance according to consumer testing. Therefore, not only that WaterSense regulates maximum flow rates, it defines minimum flow rates as well. After measuring flow rates of shower head at 80 psi to make sure it is below the maximum rating, it then measures 45 psi and 20 psi which represents the low end and very low end of possible water pressure. If the shower head have mode-switching function, it is measured with the mode that has the maximum water flow possible.


The flow rate at 45 and 80 psi the tested flow rate cannot be less than 75 percent of the shower head’s maximum rated flow rate value and at 20 psi the tested flow rate cannot be less than 60 percent of the shower head’s maximum rated flow rate value. WaterSense flow rate is also measured at 38 degree C.


Here's a break down of shower head minimum flow rate vs. pressure should be for a WaterSense certified shower head.

Example of minimum allowed flow rates

80 psi water pressure

45 psi water pressure

20 psi water pressure

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