Reverse Osmosis FAQ
These are questions that people frequently ask about reverse osmosis.
What is reverse osmosis?
Reverse osmosis, often referred to as RO, is an advanced water
purification method that was initially developed by the U.S. Navy to
produce drinking water from sea water for submarine crews.
It is a membrane filtration technology that works by forcing water
under pressure through the very tiny pores of a semi-permeable membrane.
Modern reverse osmosis units for the home combine membrane technology
with carbon and mechanical filtration to produce highly purified,
great-tasting water.
How does it work?
In modern home RO units, water, driven by normal city or well water pressure, flows
first through a carbon pre-filter, which removes organic contaminants
including chlorine and its by-products.
Next, it enters the reverse osmosis membrane, a very tight, sheet-like
filter, that allows water to pass but rejects dissolved solids like
sodium and impurities like lead and arsenic. Some of the water entering
the unit is used to cleanse the membrane surface and flows to the
kitchen drain pipes.
The purified water is stored in a small storage tank until it is
needed. When the ledge faucet mounted on the sink is opened, the
purified water is forced by air pressure through another carbon filter,
which gives it a final polish, and from there to the ledge faucet.
(This is a simplified description of a three-stage RO unit. Additional
stages like sediment filters and additional carbon filters can be
included. The simplified description omits a few very essential parts
like flow control devices, check valves, and an automatic shutoff
devices that stops the inflow of water when the storage tank is full.)
Is a reverse osmosis unit like a distiller?
Both effectively reduce “dissolved solids” content of water, so the finished product is similar, but the processes are quite different.
RO filters water through a very tight semi-permeable membrane. A
distiller is like a big tea kettle: it boils water, catches the steam,
condenses it, and captures the resulting water. Most impurities are left
behind in the boiling chamber.
Both distillers and reverse osmosis systems rely heavily on carbon
filtration for chemical removal. (Cheap distillers often have little or
no carbon filtration and are, therefore, of limited effectiveness.)
But isn't distilled water purer than reverse osmosis water?
Distillers typically remove a few parts per million more of common mineral constituents like sodium.
However, distillers don't do a good job with volatile chemicals with a
low boiling point. Chloramines, for example, which many cities now use
instead of chlorine as a disinfectant, aren't removed well by
distillers.
Reverse osmosis, with the carbon filters that accompany it, does a very
good job with chloramines. Unless volatile chemicals like chlorine are
removed by carbon filtration before they enter the distiller, they will
be released into the room air or they will end up in the distilled
water.
But in general, distilled water is very pure, as is reverse osmosis water. We aren't trying to suggest that distillation makes great drinking water.
A guy told me reverse osmosis units waste a lot of water…
Is that true?
It depends on what you mean by waste.
A home RO unit uses water to clean itself and wash away impurities.
It's like a lot of other water-using appliances. We use water to wash
clothes, to wash dishes, to wash cars, to flush toilets, but we usually think of this as water that is used, not water that is wasted.
A reverse osmosis unit uses more water in its operation than you
actually consume, but it normally doesn't use enough that you'll notice it on
your water bill. It uses water only while it's filling its storage tank.
When the tank is full, the whole unit shuts down and no water runs to
drain.
In terms of expense, it's like a couple or three extra toilet flushes a day.
And, we should mention, RO membranes are getting better and many new membranes are quite water efficient.
Can I hook the reverse osmosis unit to my refrigerator/icemaker?
Yes, if you can reach it with a ¼" or 3/8" tube from the undersink RO unit. We normally supply a refrigerator hook-up kit without charge if you ask for it when you purchase the unit.
Pressure is a consideration with some refrigerators, so it's a good
idea to check with the refrigerator manufacturer. The pressure you'll get from the RO
unit is about ⅔ of the incoming tap water pressure.
How long will a reverse osmosis unit last?
Virtually forever if you service it regularly and replace parts that wear out, like the storage tank and the ledge faucet.
Typical membrane life is about 3 to 5 years, depending on the nature of the water that it's processing. Filter cartridges should be replaced at least once a year.
Some Reverse Osmosis units make 75
gallons of water a day, but some only make 12 or 16, yet the cost is
about the same. — Why would anyone buy the low producing RO unit?
More isn't always better. If you need 75 gallons a day, then you should
buy the high output unit. But if you're only going to use 3 gallons per day,
a lower production membrane will probably last longer and do a better
job because it gets to run longer and spends less time sitting idle.
Reverse osmosis membranes clean themselves as they process water, so
it's really healthier if the membrane has to work longer to fill the
tank.
Think of it this way: If you draw off a gallon of water, a
24-gallon-per-day membrane will refill the tank at the rate of about a
gallon per hour. For most users, that's plenty fast.
A guy who sells filters showed me a chart that said reverse osmosis doesn't remove chlorine. Is that true?
That guy may someday be president, because technically what he said was
true, but for practical purposes it's an out-and-out lie.
It's true that the reverse osmosis membrane doesn't remove chlorine. It
doesn't have to, because it has a couple of high quality carbon filters
with it that do the job. In fact, if the first carbon filter didn't
remove virtually all of the chlorine, the membrane would get eaten alive in no time.
Statements like this are an obvious effort to deceive. It's surprising
that some very large companies repeat such misrepresentations just to
sell their products.
The same guy told me that reverse osmosis
units remove minerals that are essential to health. Is that true or is
he again twisting the truth?
It's true that RO units remove minerals—about 95% of the mineral
content anyway—but he isn't really telling you the whole story.
The mineral issue is probably the most controversial question in
drinking water purification. Experts on both sides of the issue speak
convincingly.
My own view, after reading much of the expert opinion, is that the
mineral content of water—either high or low—isn't nearly as important as
they would have you believe. That is, minerals in water are inorganic
and hard for your body to use. You get most of your minerals from food,
which provides organic, easily assimilated minerals.
The human body is a sophisticated instrument capable of adapting to a
wide range of circumstances and capable of thriving in areas having
water of high or low mineral content. As long as water is palatable,
it's within the body's acceptable range.
The main issue with water is chemicals, not minerals. Whether water
contains 30 or 3 parts per million calcium isn't really significant, but
the difference between 0.5 and 5 parts per million chloroform is of
life or death importance.
Do reverse osmosis units need electricity?
No, they run on tap water pressure. You need electricity only if you add an
electric pressure-boost pump or an ultraviolet lamp. Standard units
have neither and normally don't need them. Electric booster pumps are needed only if the home's water pressure is very low.
Why are reverse osmosis units so popular?
Because they produce great-tasting, very pure water at a very reasonable cost and in a trouble-free, fully automatic format.
We've found that RO customers are very loyal. And the most frequent
comment we get is: “We drink so much more water than we used to.”
Why do some reverse osmosis units cost $1300 and others cost $189?
Beats me. Especially the $1300 ones.
The thing about getting what you pay for is true sometimes, but not
always. Often the more expensive RO units are actually inferior. Many
use undersized filters in an effort to achieve a stylish appearance. And
they often have some bells and whistles that are more trouble than
they're worth.
An obvious example here is the “smart faucet” that contains a
light that is supposed to signal the need for membrane replacement. What
you usually end up with is a mediocre faucet with an unreliable
dissolved solids meter built in. Soon the light doesn't work and you
have a mediocre faucet that will eventually cost $125 to replace. We
prefer to give you a great faucet and a
hand-held dissolved solids tester that gives you an accurate, digital
reading of your unit's performance rather than a red or green light. (We
also hope you'll test your friend Bob's water with it and tell him he
needs one of our RO units.)
A reverse osmosis unit is mainly a couple of carbon filters and an RO membrane. That's 3 stages. A 4th stage would be a sediment cartridge to protect the first carbon filter. That's 4 stages. After that, everything is mainly marketing. Beware of seven-stage RO units. There are a lot more cartridges to buy and change and a lot more things that can go wrong. In most cases a 3-stage RO unit is the very best.
As for the $189 unit, what you usually get is the least expensive part
available, the bottom of the line, in every category. That's not to say
that all of the parts on the $189 unit are bad. But using the faucet again as
the example, a really good faucet costs just a little more than the one used on the $189 units and the excellent faucet lasts for many years. The cheap one has to be replaced in about a year. The more cheap or missing parts the cheap unit has, the sooner it will fail. A good consumer tip would be always make sure the RO unit you're looking at has a shutoff valve on the storage tank. Most cheap units don't. The manufacturer saved a couple of dollars by leaving it off, but the owner will have to drain the storage tank any time any work or cartridge replacment is done on the unit.
Anyway, we build the best RO unit we can and sell it for the what we
have to get to stay in business and try not to worry about what everyone
else is doing.
