How Much Water Does Reverse Osmosis Waste?

Reverse osmosis is a popular type of water filtration in America. It is used for both residential and commercial water filtration. Reverse osmosis is great because it is easy to maintain, removes impurities, saves money, and improves the taste, odor, and look of water.

Does reverse osmosis waste water?

A reverse osmosis system uses more water than it produces. To produce one gallon of RO water, gallons of water are sent to the drain. It is just part of the purification process.

So, yes, reverse osmosis technically “wastes” water (water is sent to the drain) compared to other water filtration in which all the water that goes in ultimately goes to your tap (minus the contaminants).

Some folks see the water usage as one of the biggest disadvantages of reverse osmosis. Another way to look at it though is that there are other activities that “waste” all of the water used. For example, when you run the dishwasher or washing machine, or take a shower, 100% of that water is sent to drain. So it really is a matter of perspective.

Reverse osmosis is not this evil, careless method of water purification. It’s just important to keep up with proper maintenance (change your membrane regularly) and do your homework when purchasing a system to make sure it’s the latest, most efficient technology to cut down on uneccessary water waste.

The amount of water used by a reverse osmosis system is ultimately based on the RO system itself, age of the system, and what is in the incoming water.

Nowadays, there are reverse osmosis systems that are designed to waste minimal to zero water (read more about these below).

Many reverse osmosis manufacturers do not openly disclose their production ratios probably because they can be high and it would probably scare customers away. If a manufacturer does not state the production ratio definitely ask about it before purchasing a system. The production ratio does depend on a variety of factors (as mentioned above) but a manufacturer should be able to provide a good estimate as to how many gallons of reject water there will be for every one gallon of RO water produced.

Membrane recovery rate impacts how much water a reverse osmosis systems uses. The recovery rate is how much water is being “recovered” as RO water. The higher the recovery rate, the less water that is being sent to the drain as waste water. However, some RO designs cannot handle high recovery rates – it leads to scaling and premature membrane fouling. So bear this in mind if the manufacturer is stating an exceptionally high recovery rate.

Most residential RO systems have an actual recovery rate of 10-25%, even if a manufacturer claims a membrane has a 95% recovery rate. The recovery rate is what would be recovered if the incoming water is virtually perfect. Let’s face it: very few, if any of us, have perfect incoming water otherwise we probably wouldn’t be considering an RO to begin with.

This chart shows approximately how many gallons of water could flow to the drain per gallon of RO water produced under normal water conditions.

Amount of water sent to drain (“wasted”) per one gallon of RO water produced

RO System	Brand new system	1 year old system	2 year old system	3 year old system
HydroGuard (HDGT-45)	3 gallons	5 gallons	8 gallons	10 - 25 gallons
Watts Premier (5SV)	3 gallons	5 gallons	8 gallons	10 - 25 gallons
Whirlpool (WHER25)	3 gallons	5 gallons	8 gallons	10 - 25 gallons
iSpring (RCC7)	3 gallons	5 gallons	8 gallons	10 - 25 gallons
Other ROs	10 gallons	10 - 20 gallons	10 - 25 gallons	10 - 25 gallons

You’ll notice that as a system ages, more water flows to drain and is “wasted.” This comes down to the membrane. With usage (and time) the membrane is filling with more and more contaminants so in order to continue to produce pure water, more water is sent to drain.

A membrane should be replaced every two to three years. Once you replace the membrane, the efficiency improves and less water goes to drain. For example, if you replace the membrane in the HydroGuard system at year two, the ratio would return to three gallons of water wasted per one gallon of RO water.

What is Reverse Osmosis?

A reverse osmosis (RO) water purification system separates pure water from contaminated water by removing ions, molecules, and particulates from drinking water. A reverse osmosis system improves the taste, odor, and look of drinking water. A reverse osmosis filter has a pore size of approximately 0.0001 micron.

Most reverse osmosis systems have the same basic components and work in a similar way, but the quality of their components can vary greatly. Make sure you are purchasing a quality system.

A quality reverse osmosis (RO) system provides:

Healthy, safe water. An RO system removes harmful contaminants such as metal ions, sodium, chloride, copper, chromium, and lead. Reverse osmosis may reduce arsenic, bacteria, fluoride, radium, sulfate, calcium, magnesium, potassium, nitrate, phosphorous, protozoa, and viruses.
Clear, refreshing water. Not only is RO water safe, it tastes great! Other water may be cloudy due to sediment and particles, but the reverse osmosis process removes these particles producing water you can truly see the difference in.
Financial savings. Forget a water filter pitcher or faucet filter- these are cheap temporary solutions that do not deliver purified water and end up costing way more than a reverse osmosis system in the long run.

Best Reverse Osmosis System

Enjoy clean, safe drinking water with the HydroGuard HDGT-45 series reverse osmosis system. This systems offers the filtration capabilities of a conventional 5 stage RO system, with the advantage of less filters to replace making it a more cost effective system. It reduces the levels of lead, nitrates, cysts (cryptosporidium, giardia), arsenic, sodium and more. This reverse osmosis system has a compact design, is easy to install, and uses sanitary quick change filters which makes changing water filters fast, convenient and sanitary. One of the revolutionary features of the HydroGuard HDGT-45 is it’s leak detector shut off valve (FLOWLOK ™) which silently guards against any water leaks which may occur. It also has a water pressure regulator to protect your system from water hammer and spikes in water pressure.

Ultrafiltration: A terrific alternative to reverse osmosis with zero waste water during the production process!

The Premiere PS-PURUF ultrafiltration system easily takes the place of outdated reverse osmosis and ultraviolet systems which can have significant waste water issues. The PS-PURUF produces ZERO waste water in the production of filtered water. This is the perfect water filtration system for places with water use restrictions including California. It produces water on demand (1 – 1.5 gallons per minute depending on your incoming water pressure) and no storage tank is required. This means no bacteria growth (tanks are notorious for bacteria growth) and significantly less space required. The PS-PURUF works well under low pressure conditions.

We originally published a version of this article in February 2017. We’ve changed and updated this article with more information about reverse osmosis, the latest figures of how much water reverse osmosis uses, and the best RO system for 2020.

Author
Recent Posts

Whitney

Whitney is a water filtration blogger with over 10 years of experience in the water treatment field. She started off in the office for Premiere Sales many years ago, and her interest and technical knowledge in water filters grew and grew. Nowadays she leads customer care and technical product support, and even helps develop new water filtration products. She completed her Media Communications MA and MBA degrees at Regents University London. Whitney is on a mission to help people easily understand and learn about water filtration.