High Pressure Shower head and water saving of the future

Updated: 3 days ago

TL; DR: high pressure and water saving can co-exist in showers, in 2022 user-centric designed smart shower technology will make showers great again.

Climate change is upon us, whether we’d like to admit it or not, and as its impact starts to trickle down to people’s households, everyone is starting to feel the pinch. One of the most significant aspects of our lives that has been impacted is water. US water prices have almost doubled in the past decade, roughly 20 to 70 percent of the U.S. is experiencing more recurrent dry weather conditions. What was previously abnormal is now becoming a regular occurrence. As the Chief editor of MIT technology Review Matt Honan stated, most of us will first experience climate change through water, we will flood, or burn or both, indicating that extreme drought or flooding would become a norm.

Showering uses on average 20% of all household usage and is the most water consuming activity everyday. For a normal family, you can easily use up to 1000 gallons of water in just showering alone each month. Moreover, shower water is usually heated water, which means that more energy is consumed during shower versus using a garden hose, or flushing a toilet.

Where have all the high pressure showers gone?

To avoid extra water usage or unnecessary water usage during showering, a maximum cap of 2.5 gallon per minute (GPM) at 80 psi house water pressure for shower heads was introduced nationwide in 1992. This led to the U.S. The Environmental Protection Agency (EPA) has been running a WaterSense Program since 2006 that further defines shower head flow-rates to 2.0GPM at 80 psi. WaterSense is a voluntary partnership program that labels water-efficient products and resources for helping you save water across all different products.

For shower heads, the WaterSense ensures that the maximum flow rate is capped, it also regulates the percentage of flow rate decrease and takes into account house pressure drop so that you would still have a somewhat decent shower flow when your house water pressure isn’t that high. It’s clear that WaterSense appreciates that a certain amount of water pressure and flow is needed for one to properly rinse.

Since it’s a voluntary program, states, counties or cities can decide whether they want to partner with WaterSense to help residents and businesses to lower water consumption. This is usually based upon geo-location differences, requirements and regulations that differ in different areas.

For example, where Oasense is located, in California, the shower heads that you can purchase will only have a maximum flow rate of 1.8 gallons per mins. It's not possible to buy a 2.5GPM shower head in home depot, nor purchase one on Amazon and ship it to California. There are places that have tighter regulations or looser on flow rate. And whether WaterSense compliance is required. For example in the States of Colorado, showers sold need to be at 2.0gpm rating at 80 psi and also need to be WaterSense certified, but in Arizona, the shower head needs to be at 2.0gpm but WaterSense Certification is not required.

Here’s a table based on the latest regulation of shower heads we compiled, credits to Neoperl who makes good flow restrictors and help products to have good flows during low pressure for providing data. You can also visit here to see how shower is tested by WaterSense Please note that these plumbing codes are subject to change, and we compile the latest regulation on shower heads for you as of Jan. 2021, you can also read more about detail WaterSesne testing here:

Highest allowed shower head flow rates per states and cities, 2022

Now we know why in some areas we cannot get high flow rate shower heads like our parents used to have. In the future they will no longer be available to anyone.

Low flow rate means low pressure

We have been addressing flow-rate of different areas in the country, but a more common term we use to describe good shower experience is “pressure”, which is actually not a very stringent scientific term. We won’t go into complex fluid dynamics, but we will try to explain this in layman's terms; we can easily comprehend that all the “pressure” we feel from shower is total force of the water droplets hitting our skin. If we limit the total amount of water allowed into the showerhead from the start (which is the definition of flow rate), no matter how we squeeze the nozzles to increase the flow rate out of the orifice, it can not get much higher, hence the "pressure" of the shower is limited.

Although not in an ideal world, water flow rate follows the continuity equation roughly:

Q (gallon per mins) = A1 (area of the standard half inch pipe)* V1 (water flow rate into the shower head) = Sigma A2 (area of nozzle orifice)* V2 (water flow rate out of the nozzle orifice)

Imagine a rubber garden hose is in our hand with water flowing, if we squeeze it, the total area (A2) becomes smaller and hence the flow rate (V2) becomes higher and we would see a somewhat higher pressure water stream. However, the total amount of water flowing out can only be less. And if the tap is half opened, no matter how we squeeze the hose, the pressure can not be increased too much.

Now consider the shower, same principle applies, if the total gallons per min, Q here is limited, no matter how tiny the the nozzle orifice becomes or whatever tricks that companies wants their consumers to believe, say vortex shower head, mist shower heads, jet-like showers, the experience just can't be as good as before. No matter how we change the nozzles, a 1.5 gpm showerhead would have no comparison to a high flow, 2.5 gpm showerhead, because the source of water is limited.

Shortcomings of nozzle engineering

Now that we know that the high water pressure we are feeling is actually the total force of water that reaches to our skin and that this is actually determined by water flow-rate and physics of the continuity equation, it would be easy for us to understand some other draw-backs from common high pressure yet water saving shower heads. Simply put, there are no shower heads that increase pressure without draw backs.

  1. Total water coverage is small and total water coverage areas are limited. In order to get a jet-like pressure, low flow shower heads often designed very focused water streams with very few nozzles so they can concentrate all water and burst them out so you at least get a decent rinse.

  2. Water gets cold very easily. For example, some of the filtered showerhead that uses laser drilled metal pin-holes or furthermore, some of the misting shower heads or shower systems, because of the water droplets are so tiny, the total surface area of water contacting cold air increase a LOT, therefore water get cold very fast. When you move slightly away from the nozzles while showering, you would feel a sudden the temperature drops. Even worse, you probably are asked and have to raise your water temperature setting at your heating tank or tankless heater temperature, which basically causes more energy and defeats the purpose of conservation.

Low flow shower heads could not be saving that much

One more common problem of low flow shower heads that people face is prolonged showering due to lower flow rate. (Koomey JG, Energy 20(7):627–635). It just takes that much water to dissolve the soap. If you decrease the water flow, then shower has to become longer to get the same about of cleaning, and thus offset the savings.

Another interesting study pointed out by evolve technology and the Lawrence Berkeley national lab is that the lower the flow rate, the slower the cold water in the pipe will be pumped out, and more losses of energy would happen during the entire system., in this study, it is showed that if we limit shower flow rate to 1gpm, it will waste up to 50% more of hot water during the warm up phase.

Over-limiting shower flow rate can be devastating for shower experience, not saving as much water because of the necessity of longer rinse, and more energy losses during warm up phase.

Future of high pressure showering and water saving, in a smarter way

In designing our truly smart shower Reva, we thought that the that best way to for people to enjoy high pressure showering and save water is not to take the low-flow approach like some of our friends with misting sprays or extreme concentrate beams or vortexes that look cool but don't really do much. We wanted to deliver an old school feeling, good flow, good coverage, and still be able to save water by concentrating all the water during rinsing and shut off the extra flow when you don’t use it through our tech integrated shower. We think that technology really benefits people by providing more than just LED lights as a shower timer or shower shut off timer, or just data streams over bluetooth that you would get excited the first week about the data but soon forget about the app in your phone months later. We want to have an interactive water saving experience that you can save without moving a finger and just enjoy a good shower.

We used a special engineered embedded sensor. Very much like a sensor faucet that you are familiar with, but a lot more. Learn about our sensor technology that enables the highest efficiency shower head here.

When starting the tap, our temperature sensor would start sensing the water temperature, and when the temperature reaches your tap setting, yes we detect that as well using mathematical approaches processing temperature data, the water flow turns into 10% of the maximum flow. That saves the behavioral wastes of 10 percent instantly. You can be replying to texts, watching the news, checking emails or finishing that last drop of beer or coffee without worrying about the water, money, or energy that would usually just pour down the drain unused. '

Once you are ready to shower, just step into the flow and our sensor will detect you and shower you with a full cascade of water. When you need to lather up, shampoo or shave, just take a step back and water flow will reduce to 10% again. It’s giving you the key to save water on your own terms, to be able to rinse as freely as you wish without having to compromise on experience with a typical low-flow showerhead. The technology needs to be able to design around user experience instead of limiting it. We think that this is how a true smart home product in 2022 should look like, addressing the issue, and keeping the good experience. We believe that Reva is the future of shower head design, and this is how we can enjoy and tackle water issues everyday at home.

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