Comment by dingleberry | Hacker News Reader

Comment by dingleberry | Hacker News Reader

I've used reverse osmosis unit for years. new unit is less than $100usd it paid itself in months. maintenance is cheap.

my RO has kinda low efficiency. 4 units of water in, i get 1 unit of clean drinkable water. 3 units are 'waste' (don't believe what socmed says, it's not dirty). the waste water is used for laundry, aquarium and gardening. my fishes and vegs are thriving.

to test purity, just plunge the ohm meter probes into a cup of ro water. if the resistence is in 1MOhm, it's pretty pure. mountain/mineral water bought from store is about 150kOhm. after drinking ro water for a while, store-bought water tastes slightly salty.

my house pumps water from ground (well-pump). for a family of 6, i need 1m3 of water. that's about half hour of 500W pump. an ro unit (40W) runs about 3 hours for 5gal bottle. so give or take, 1/2kWH or about 15KW per month. that's about $1 or $2 for my water need per month.

if i must buy raw water (such as living in an apartment), it's about $1 per m3, so about $30 per month; however, i get drinkable water too. ro units are portable. i saved $28/mo in water expense after moving from apartment.

flashing back from memory, i used to lug around 3 5gal water-cooler bottle from stores to my apartment every 3 days (i had 3 bottles). it was not pleasant and wasted time (go to store, queue, lug heavy bottles back)

ro unit has relay so you don't have to sit and wait for it to fill. it automatically cuts power to the pump when its internal clean-water-tank is full.

I was instructed (from professional chemists) to NOT drink 1 MOhm ( or other highly-purified) RO water. At that purity, particularly when hot, it will leach metals and other compounds from pipes, pots, cups, etc. Maybe it's worth dropping a little salt into the water after purification?

I'm also surprised that you use the waste water on your aquarium. In my experience, fish are MUCH more sensitive to water quality than humans are. This is particularly true for corals in saltwater tanks. In fact, many aquarium stores sell RO-purified water for fish tanks!

I do not see why extremely pure water would leach metals any more than tapwater would. Chemically it should not matter. All species will reach equilibrium between the surface of the container and the liquid and if dilute they will not care about one another. That equilibrium will be reached faster if the temperature is higher.

What is true is that you should not drink hot water from pipes because hot water does leach metals, tapwater or otherwise.

Was this not the issue in Flint, Michigan with the water leaching lead because it DIDN'T have something in it?

No, the water there was more acidic than the prior water the system used, causing leaching.

I see; thanks.

Very pure water is corrosive.

I built a CVD lab that had aluminum deposition chambers plumbed into a DI water cooling system. The water was fed from a purifier that provided 18MΩ-cm water.

The water corroded the aluminum chamber cooling passages, leaving aluminum hydroxide behind. This conversion of metallic aluminum to a gelatinous, clogging hydroxide was what alerted us to the problem. Feed pressure (regulated) was fine, but flow rates fell and chambers heated up.

We had to wire brush all cooling channels, a total pain. We ran on tap water for a couple of weeks while we researched the issue, and had very little corrosion but had other issues (mineral deposits).

Finally, we reverted to 18MΩ water and added ~10% volume of ethylene glycol (antifreeze, basically). Once we "degraded" the water purity with glycol, our corrosion problems stopped. It was very counterintuitive.

Here's an industry source that has a little bit to say about the corrosive properties of pure water:

http://www.lytron.com/Tools-and-Technical-Reference/Applicat....

Given the industrial importance of the problem, I'm sure there are in-depth chemistry explanations. Haven't pursued them.

Drinking just RO water isn't the healthiest thing because the RO removes the useful minerals too, and that's why there are add-ons to most RO systems for re-mineralization.

http://www.survivopedia.com/how-to-re-mineralize-water/

http://www.waterbenefitshealth.com/reverse-osmosis-water.htm...

just eat plenty of vegetables and fruits. they contain minerals and more palatable.

No, the point is we never normally drink totally pure water, we nearly always drink mineral water. Mineral water does in fact taste better most of the time. Pure H20 is going to start dissolving all sorts of stuff from it's surrounding, making it taste odd.

They are right. 1 MOhm water will jack the minerals off your teeth. OP would be lucky to not have cavities forming right this second.

i do have cavities on back of my lower jaws; however, it's not due to RO water. should RO water is causing this, the damage distribution should be uniform -> my other teeth should be equally damaged.

i still have other teeth intact, no holes, despite using ro water for 8 years or so.

i think there's the cause of my holes. i had wisdom teeth very late in age. my brushing pattern wasn't sufficient. moreover, i was addicted to oatmeal power drink and didn't brush after. those sugary flakes seem to linger on my back jaws.

yudkin book, "pure, white and deadly" discusses this. children who drink sugary vs eating candies. same sugar; however, those eating candies get more cavities simply because candies stick between teeth ... think twinkies

on interesting part of the book is about the slave in sugar plantations. they did eat raw sugar; however, the slaves didn't get the same disastrous level of disease as the masters, who eat refined sugar.

Cavity damage isn't uniform though. It depends on location of exposure and the way the mouth salivates. It makes sense that the cavities are toward the back of the tongue. Anyhow, I would be careful. Just get a potassium chloride rock and throw it in the water. No biggie.

How could that be the case? Tap water is nowhere close to mineral saturation. It should make an astronomically small difference. If anything, it could be less corrosive due to the higher resistance.

I do see a possibility for it to be slightly more corrosive in pipes under specific circumstances, due to the lack of anything forming a passivating layer on the long run. But for teeth I have a hard time believing this.

Are you kidding me?! Tap water has to go through dirty city pipes. Of course it's saturated with minerals. Not only that but Fluorine or Chlorine or whatever halogen they choose to kill the bacteria and protozoans with.

What I meant with saturation is the state when no more minerals can be absorbed.

Dissolution is based on concentration of existing solute. This isn't a binary effect of complete saturation like you suggest. Pure water has enough diffusion pressure to cause significantly more dissolution of a tooth's mineral lining than hard water. Diffusion pressure of pure distilled water is 1236 atm.

See DPD: https://en.m.wikipedia.org/wiki/Suction_pressure

Quote on quote: "If some solute is dissolved in water its diffusion pressure decreases. The difference between diffusion pressure of pure water and solution is called diffusion pressure deficit (DPD)."

i used to store hot water in thermos that the inside glass got stain from hard water (apartment water was hard, contains a lot of mineral)

after i got a son, we replaced hard water with ro water, including the thermos. well, baby is important, right?

over time (months), the stains are gone, the glass inside the thermos got cleaner.

so yeah, ro water being soft water probably cancels out the stains from hard water previously used.

on waste water for aquarium: it's because you misrepresent 'waste water'. water in an ro unit gets filtered four times (must go thru 4 different filters). the first is sediment, and the last is the ro membrane. can't remember the middles.

the sediment filter gets brown over time and need to be replaced (cheap, ~$1 per cylinder). so there's some impurities captured.

after last filter, the membrane, the water that fails to pass becomes 'waste water'. it's actually clear, tasteless, just didn't pass the ro membrane.

so ro waste water is actually cleaner than the input water. my fishes are okay with water from well. naturally, they should be okay too with water that's cleaner than well water.

on heavy metal, fishes are very sensitive to cu, not so much for pb. so if fishes are healthy and not jittery or die after a day, the water should be okay.

i also bought ro unit for my soft-water fishes: neon tetra. accidently, i found that human can drink ro water too ;)

It's not a theoretical issue, and not limited to RO water supplies. Here in Portland Oregon the municipal water source is Bull Run Watershed high up in the foothills of Mt. Hood, some 26 miles east of downtown.

The collected water is basically similar to distilled water since it's formed directly from cloud/fog condensate. Consequently the default pH is ~6.8-7.0, which leaches lead from old plumbing. The federal government forced the city to add sodium hydroxide to increase the pH to ~8.0 and reduce corrosion.

Obviously city water has very little dissolved solids which in principle could have health implications re: Ca, Mg intake. Diet is normally the main source of these minerals, not clear how much additional risk is attributable to low mineral content of household water.

Most people here consider our water to be very palatable as is and are reluctant to have further modifiers applied to it. If any new federal requirements are attempted it's likely to elicit a lot of controversy and pushback.

You are ROing potable water from a well not from an ocean or sea. Costs and requirements much different.

yeah, costs and requirements will be higher for saline water.

That's really cool. Do you face any regulatory issues for your pumping? Do you have to own water rights on your land to pump from the ground? Have you ever had your groundwater tested to ensure that there are no contaminants that might not be filtered by RO?

water from well is okay for home use; however, for hotel, you need permit.

i'm not overly concerned about contaminants because my water source is at the back of my house which has big trees, not some deserted mines.

likewise, i never really question the safety of spring water bought from store. my crude experiment say that it's purer than spring water. that's should be sufficient.

as far as i know, spring water is just that, water from spring, untreated.

FWIW, it is typical for anyone who lives outside of a city to have well water. I would be shocked if there were any regulatory issues with doing so anywhere in the US, or any issue with water rights. There are millions of people doing it right now.

I think hypothetically when the system is first installed it's supposed to be tested, but I don't put a lot of faith in that. Interestingly, in contrast to parent, it's pretty standard for the water to be totally unfiltered. Generally, you have an electric pump that cuts on any time the water pressure drops below a certain level to maintain it. Honestly I've no idea how much it costs me a month, but it's pretty nominal. My electric bill runs about $125/mo and most of that is the AC.

(In case you were wondering, sewer is dealt with via a septic system, which still amazes me. All your wastewater drains into a ~1000 gallon tank buried in the ground. At the top of the tank are field lines, which distribute water and drain it over a wide area. Solids are rapidly broken down by bacteria in the tank and quickly dissolve. These systems can be maintenance-free for 25 years, though the septic industry recommends you pump them every several years to remove "sludge" that slowly accumulates at the bottom.)

to get water from ground, drill a hole about an inch diameter so long pipe can be inserted.

if you can get good water within 9 meters, that's great because standard pump can suck up to 9 meter down.

if you get salty, rusty, smelly colored water, drill deeper. 30m is pretty much max depth for home-use jet pump and normally you get clean water.

you can get deeper too and use bigger hole too; however, that's when you need permit. industry and hotel often do because they need a lot of water very fast.

water collected from pump can be stored in large tank above roof. then gravity plays it part delivering tank-water.

there's a switch on the tank that cuts electricity to the pump when a buoy inside the tank float up to a certain level. so, my switch is simpler water-level-based, not pressure-based.

from empty to full, my pump runs about 30 min. my pump is 1 horse power or about 750w. so for a month that would be 30 * 30/60 * 750w = 11.25 kwh.

for disposals, my house get two lines. one for washing, bathing, etc and that goes to city sewer. another is for human waste that goes to house ground sewage tank.

sewage tank is basically an unsealed empty space inside ground. bacteria decompose human waste and the water just get filtered by ground beneath. the tank gets full over time and sewer tank service can come and suck the sewage tank.

Why are you filtering well water? What's wrong with it unfiltered?

Why did you buy water at a store when you lived in an apt instead of using city water?

nothing wrong, when i was a kid, i often drink well water directly uncooked. i filter it because now i can and i have a son.

well water are already filtered by nature. the deeper the well, the cleaner the water is. think spring water, which is rain water filtered by hundred-meter rock hill.

water in apartment often smell funky and can't be trusted (management mix water from its own water-treatment with government water).

i know for sure how nasty the apartment water because i often pour pure-strength (not grocery-bought) HCl or NaOH (wait for a day so they don't cancel out) down the drain when it's clogged in hope they dissolve matters.

the pipe still sometimes gets clogged after harsh chemical treatments so lately i just use thick-liquid SLS (or use downy super in the USA, or any concentrated detergent) and pour hot water. it moves clog point down further the apartment pipe. slippery it is!

i used to have my sink flooded within 10 seconds. now it's after 60 seconds, leaving plenty of time to do quick washings.

that's history because now i live in a house.

Wow, that's really interesting. Do you have other tricks you use for efficient homesteading? Using solar and whatnot?

How do yo check the resistivity, does it not depend of the distance? Is it 1MOhm/m?

i standardized so that distance is not important. just use dry cup, plus and minus probe on tip opposite each other, dip probes to the metal end.

it's not scientific, no replication, i did not even double blind myself and randomize. it's lazy, just for fun.

Reply on news.ycombinator.com