Updated: Nov 21
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.
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.
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
Although buying a WaterSense certified shower head means a lower maximum flow rate, but it guarantees the flow rate at low pressure so an acceptable rinse performance can still be achieved. And finally, the highest flow rate allowed by WaterSense is 2.0 gpm for shower heads.
How many gallons of water does a shower use?
Average American shower for 8.2 mins long. Considering shower head flow rate typically is between 1.8 gpm to 2.5 gpm, if we use 2.2 gpm as a medium number, and consider the pressure drop (remember that all shower heads are rated at 80 psi, but house pressure typically are not at 80psi), then the shower usage would be somewhere between 16.5 gallons to 18 gallons . Obviously it varies between everyone, but 17~18 gallons would be a very good answer.
Maximum flow rate and WaterSense requirements for different regions 2022.
Here is a complete list of highest GPM shower heads allowed other than the 2.5 gpm national standard. Higher flow rate shower heads can not be shipped to locations where flow rate mandates are enforced. Please note that plumbing codes do change and we might not be able to keep up to date on the latest regulation. For the most up-to-date information, check with the local municipal offices.
Scottsdales, Arizona - 2.0 gpm
West Hollywood, California - 1.5 gpm
California - 1.8 gpm
Ft. Collins, Colorado - 1.8 gpm & WaterSense certified for new constructions
Colorado - 2.0 gpm & WaterSense certified
Miami-Dade County, Florida - 1.5 gpm & WaterSense certified
Broward County, Florida - 2.0 gpm & WaterSense certified
Hawaii - 1.8 gpm
Chicago, Illinois - 2.0 gpm & WaterSense certified
Massachusetts - 2.0 gpm
Rockville, Maryland - 2.0 gpm
Nevada - 2.0 gpm
New Jersey - 2.0 gpm & WaterSense certified
New Your City - 2.0 gpm & WaterSense certified
Oregon - 1.8 gpm
Vermont - 2.0 gpm
Washington - 1.8 gpm
Washinton D.C. - 2.0 gpm & WaterSense certified
More rinsing and automatic shower saving
Although EPA estimates that switching to a WaterSense labelled shower head could save 1,200 per shower per year, if the flow rate is too low, the shower experience could be compromised. Typically, a low flow shower head refers to flow rate lower than 1.5 gpm. Not only that these low flow shower heads have certain draw backs, it also can pro-long the shower time off-setting the water saving. After all, it needs certain amount of water to remove the soap, that is physic.
Studies have shown that 1.8 gpm is the minimum flow rate to have a good enjoyable rinsing, so the common 1.75 gpm models, is somewhat good enough for a decent shower. To save water further and still have a full enjoyable rinsing experience. Further reducing flow rate would cause some compromises in rinsing, pressure or coverage of water. Oasense Reva smart showerhead with its latest embedded sensor technology is a great way to enjoy luxury rinsing and still promotes water conservation and reduce shower water usage. Superior than other smart showers, Reva is the most tech-advanced shower head that saves water.
Learn more on how flow rate impacts shower pressure.
Learn more in general about smart shower heads.
Oasense Reva smart shower combines advance sensing, machine learning algorithm that controls the built-in shut off valve that will eliminate extra water wastes when shower is not actively in use and during warm up phase of the shower. Oasense Reva concentrates all water towards rinsing, making a 1.8 gpm showerhead effectively a 1 gpm showerhead yet still have the high pressure that every one likes. It can be installed in just 15 seconds without the need to remodel the bathroom contrary to any other motion activated shower system.
Oasense Reva is the winner of Consumer Electronic Show (CES) 2022 Innovation award, Reddot product design award 2022, Reddot innovative product 2022, and Fast company world changing idea.
Learn more about Reva showerhead by visiting Oasense or sign up and claim Oasense Reva smart shower head $35 discount here