3 ms·

It really does depend on what your water source is and the pipes from there to your tap. For example, the Hetch Hetchy water that supplies San Francisco and som

It really does depend on what your water source is and the pipes from there to your tap. For example, the Hetch Hetchy water that supplies San Francisco and some other parts of the Bay Area is very pure. Reverse osmosis is not going to remove much of anything. Davis water, or San Jose water, well, that's a little different. The other thing about RO water systems is that they are not very efficient. For every gallon of pure(-ish) water that a home system generates, it typically has to throw away 5 gallons of salty water.

cheald 3y ago
RO systems vary by efficiency, but 1:5 seems way out of whack. My tankless system claims 2:1 output:waste, and while I haven't measured it directly, I'd say that's probably pretty close to right.
- whyenot 3y ago
  "For example, a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of permeate produced." https://www.epa.gov/watersense/point-use-reverse-osmosis-systems https://www.epa.gov/watersense/point-use-reverse-osmosis-sys...
  - reducesuffering 3y ago
    This is outdated as most of the mfgs have gotten better at it. Mine is 1:1 drinking:waste and my monthly water consumption is barely affected as it's indiscernible in the noisy variation. First 4 links on Amazon I'm seeing 2:1, 2:1, 3:1, 3:1
  - jon_richards 3y ago
    I looked into this a while ago and didn't understand why the efficiency claims were so different, but here's a video of a RO system running https://www.youtube.com/watch?v=2r_T7Bgi3hQ https://www.youtube.com/watch?v=2r_T7Bgi3hQ
reducesuffering 3y ago
"San Francisco and some other parts of the Bay Area is very pure" https://www.ewg.org/tapwater/system.php?pws=CA3810011 https://www.ewg.org/tapwater/system.php?pws=CA3810011 Contains Carbon Tetrachloride, Hexavalent Chromium (PG&E v. Erin Brockovich anyone?), Haloacetic acids, and Trihalomethanes, all carcinogens. All are reduced by reverse osmosis use. You say "not efficient" when it's more like an extra 1-2 gallons waste, and yet the outcome is much cleaner water that makes up a large portion of your biology. I'd say that's a pretty efficient way to be healthier, especially when drinking water is a very tiny sliver of water consumption. The average person uses 3,000 gallons of water a month and you're sweating an extra 5 gallons for drinking?
- zdragnar 3y ago
  That's an extra 5 gallons only if it is done at the point of consumption. To do it for all water- showers, washing dishes, laundry, etc- would require RO for all potable water for the city water supply. Depending on where in California you are, that much extra water consumption (since the waste will have an even higher concentration of harmful chemicals) isn't exactly an option.
  - reducesuffering 3y ago
    This isn't common or as much of a concern at all. I'm talking about drinking water for consumption. It's a $200 expense, an extra 20 gallons of water a month at most (out of 3000).
- whyenot 3y ago
  Water quality: see https://www.sfpuc.org/sites/default/files/documents/SF_Regional_WaterQualityReport_CY2022.pdf https://www.sfpuc.org/sites/default/files/documents/SF_Regio... Efficiency: see https://www.epa.gov/watersense/point-use-reverse-osmosis-systems https://www.epa.gov/watersense/point-use-reverse-osmosis-sys... For example, a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of permeate produced. Some inefficient units will generate up to 10 gallons of reject water for every gallon of permeate produced. In recent years, membrane technology has improved and some point-of-use RO systems have been designed to operate more efficiently, with some manufacturers advertising a 1:1 ratio of permeate to concentrate production, meaning only one gallon of reject water is generated for each gallon of treated water.

cheald 3y ago

RO systems vary by efficiency, but 1:5 seems way out of whack. My tankless system claims 2:1 output:waste, and while I haven't measured it directly, I'd say that's probably pretty close to right.

whyenot 3y ago
"For example, a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of permeate produced." https://www.epa.gov/watersense/point-use-reverse-osmosis-systems https://www.epa.gov/watersense/point-use-reverse-osmosis-sys...
- reducesuffering 3y ago
  This is outdated as most of the mfgs have gotten better at it. Mine is 1:1 drinking:waste and my monthly water consumption is barely affected as it's indiscernible in the noisy variation. First 4 links on Amazon I'm seeing 2:1, 2:1, 3:1, 3:1
- jon_richards 3y ago
  I looked into this a while ago and didn't understand why the efficiency claims were so different, but here's a video of a RO system running https://www.youtube.com/watch?v=2r_T7Bgi3hQ https://www.youtube.com/watch?v=2r_T7Bgi3hQ

reducesuffering 3y ago

"San Francisco and some other parts of the Bay Area is very pure" https://www.ewg.org/tapwater/system.php?pws=CA3810011 https://www.ewg.org/tapwater/system.php?pws=CA3810011 Contains Carbon Tetrachloride, Hexavalent Chromium (PG&E v. Erin Brockovich anyone?), Haloacetic acids, and Trihalomethanes, all carcinogens. All are reduced by reverse osmosis use. You say "not efficient" when it's more like an extra 1-2 gallons waste, and yet the outcome is much cleaner water that makes up a large portion of your biology. I'd say that's a pretty efficient way to be healthier, especially when drinking water is a very tiny sliver of water consumption. The average person uses 3,000 gallons of water a month and you're sweating an extra 5 gallons for drinking?

zdragnar 3y ago
That's an extra 5 gallons only if it is done at the point of consumption. To do it for all water- showers, washing dishes, laundry, etc- would require RO for all potable water for the city water supply. Depending on where in California you are, that much extra water consumption (since the waste will have an even higher concentration of harmful chemicals) isn't exactly an option.
- reducesuffering 3y ago
  This isn't common or as much of a concern at all. I'm talking about drinking water for consumption. It's a $200 expense, an extra 20 gallons of water a month at most (out of 3000).
whyenot 3y ago
Water quality: see https://www.sfpuc.org/sites/default/files/documents/SF_Regional_WaterQualityReport_CY2022.pdf https://www.sfpuc.org/sites/default/files/documents/SF_Regio... Efficiency: see https://www.epa.gov/watersense/point-use-reverse-osmosis-systems https://www.epa.gov/watersense/point-use-reverse-osmosis-sys... For example, a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of permeate produced. Some inefficient units will generate up to 10 gallons of reject water for every gallon of permeate produced. In recent years, membrane technology has improved and some point-of-use RO systems have been designed to operate more efficiently, with some manufacturers advertising a 1:1 ratio of permeate to concentrate production, meaning only one gallon of reject water is generated for each gallon of treated water.