Reverse osmosis is a semipermeable membrane that will pass some atoms or
molecules but not others. The best common example of a semipermeable
membrane would be the lining of your intestines. The membrane allows
passage of water molecules but not salt molecules. One way to understand
osmotic pressure would be to think of the water molecules on both sides of
the membrane. They are in constant Brownian motion. On the salty side, some
of the pores get plugged with salt atoms, but on the pure-water side that
does not happen. Therefore, more water passes from the pure-water side to
the salty side, as there are more pores on the pure-water side for the water
molecules to pass through. The water on the salty side rises until one of
two things occurs. The salt concentration becomes the same on both sides of
the membrane (which isn't going to happen in this case since there is pure
water on one side and salty water on the other). The water pressure rises as
the height of the column of salty water rises, until it is equal to the
osmotic pressure. At that point, osmosis will stop.

Osmosis, by the way, is why drinking salty water (like ocean water) will
kill you. When you put salty water in your stomach, osmotic pressure begins
drawing water out of your body to try to dilute the salt in your stomach.
Eventually, you dehydrate and die.

In reverse osmosis, the idea is to use the membrane to act like an extremely
fine filter to create drinkable water from salty (or otherwise contaminated)
water. The salty water is put on one side of the membrane and pressure is
applied to stop, and then reverse, the osmotic process. It generally takes a
lot of pressure and is fairly slow, but it works.

Here is one more for you to debate. Take distilled, tap water, and RO
water. Put all 3 glasses in a microwave and see if they boil at the same
time. Pure distilled water will not boil a 212 it will become super heated.
The reason distilled doe not boil is there are no impurities in the water.
Tap and RO will boil sat the same time they both contain impurities. To
make the distilled water boil just add a little salt, sugar, or any other
impurity. Be careful it may explode back on you leaving a nasty burn.

Jack

Olly wrote in message ...
Watermakers remove almost all the TDS - supposedly 99+% - so the water
is like distilled. Is it unhealthy to drink nothing but distilled
water - no mineral content - for years while cruising.

So how would one go about building a home made water distiller? I understand the water must be boiled into steam then re-condensed into water again. Are there any house hold items I could use to achieve this? I looked online for intructions but I am unable to find any. Thanks

Davethewave wrote in
news
So how would one go about building a home made water distiller? I
understand the water must be boiled into steam then re-condensed into
water again. Are there any house hold items I could use to achieve
this? I looked online for intructions but I am unable to find any.
Thanks


All you need is a boiler and a condensor. The condensor should be made of
stainless steel so it doesn't contaminate the distilled water and add metal
oxides like copper does. Most distillers are stainless. Unfortunately,
the seawater condensor out of an extinct marine AC won't work, even if you
clean the oil out of it. A seawater condensor would be perfect if you're
into metalwork....stainless tubing with seawater water jacket. I have two
distillers here. One is a commercial unit used to make lab water. It's a
porcelain "pot", like a flower pot but white porcelain. The "unit" that
fits on it is another pot with slots around the top for intake air to the
fan, a simple fan with a 2-pole phonograph motor you'd find in any range
hood ashore. The boiler is actually a white porcelain tube with a pressure
relief hole about 2" underwater when it's in the pot. There is a 1500 watt
stainless heating element that's about 4" long and 1/2" in diameter in the
center of this tube. The tube, of course, submerges in the pot when its
full, keeping the "core" heater underwater at all times. (NEVER LET THE
REACTOR CORE BE EXPOSED!...just like 3 Mile Island.) The steam produced by
this red-hot little plug rises through the hot water into a sealed chamber
at the tube's top. The only way out is into the stainless tubing that
comes out a hole in its top..the condensor. This inlet wraps around to
become the top of a cone made of the tubing in a continuous, ever expanding
coil, like a flat coil pulled on the outside turn. At the bottom, the coil
exits the pot where a surgical 1/2" hose leads the distilled water away for
collection in a separate tank. I use 5 gallon glass jugs the water
companies deliver water in, sanitized at 220F in my oven after each use.
The fan simply blows air down on the coil cone to get the steam under 100C
and we're making water. Condensing is actually quite easy. It's so
complete no steam exits at the bottom, only hot water.

The pot is self-filling and stays full in operation. There's a small nylon
hose to a faucet fitting that plugs into a special bubbler attached to the
sink faucet. The hose goes to a float valve with a little glass float in
the pot. This float also trips a microswitch that cuts off the heating
element if the pot should drop below its working level, as when the water
is shut off, protecting the "core" from "exposure".

It makes 15-16 gallons per day if left running 24/7, at about 25c/gallon at
9c/kwh load at 115VAC.

I filter the distilled water through a column of activated carbon (fish
tank department of Walmart, 1 pound for $3.29) to collect the distillable
pollutants in tap water, such as benzene and other elements related to
benzene. Benzene is what gives distilled water its metallic taste, not the
condensor. It condenses near the temperatures of water, boiling off with
the steam. Simply dripping it through carbon grains in a coffee pot paper
filter to contain carbon dust and you get DELICIOUS, pure water that's only
about 3.8ppm total dissolved solids, about as pure as you can make it.
It's nearly a perfect electrical insulator at this purity, too! The carbon
column is also homebrew. It's a nylon, dishwasher-safe, turkey baster.
Pull the rubber bulb off the nylon tube and cut a hole in the end of the
bulb opposite the normal hole. Shove the tube completely through the
rubber bulb so you can use the bulb as a plug in the 5-gallon jug. Put a
plug of coffee filter paper as far as it will go to the small end of the
tube, then fill the rest of the tube to within an inch of the big open end
you're going to put the feed hose into. The whole thing transfers from jug
to jug hole without stopping production. You get to sleep 6 hours if you
start a new jug at bedtime. In winter, it keeps the furnace from running
with secondary utilization of the heat coming pouring off the condensor
(1500 watts). In South Carolina, it makes the AC work harder...dammit.

I also have a Sears unit that Waterwise makes:
http://www.waterwise.com/productcart...p?idproduct=24
This unit is a sealed 1.5 gallon boiler (on the left) you simply fill from
the faucet, click on the top which is a water separator/steam outlet, and
plug into the base unit making electrical and steam connections
automatically. The carafe comes with a top that has a place to put a
carbon filter cartridge they want way too much for that the water drips
through on its way into the carafe. (I used coffee filter paper with
carbon grains wrapped inside and it works fine). The carafe fits neatly
into the fridge and you can buy extra carafes to increase production.
Carafes are taste-free plastic and are priced like Lexus car parts. This
unit simply sets by the sink and makes one pot at a time. It's computer
monitors boiler current, pot positions and you just push the start button
to start it. It has a clock so you can tell it to start at some future
time....why remains a mystery. I want the water to sit in the carafe right
where it is to COOL before loading up the fridge with heat...idiots. The
unit has some design problems. They fixed one and I sent them the fix for
the other.

The original thermostats under the heating element like a coffee pot failed
often because the wires melted...duhhh.. They replaced the thermostat with
one with heavier wires welded on, thank you.

My design engineering fixed the problem of the steam seal around the top.
Waterwise used a linear piece of window seal superglued on the ends to make
the top seal. The length was too short, so the glue pulled apart on the
ends causing a leak and most of the steam condensed on the back plastic of
the main unit, running down onto the countertop...gallons of it.
Engineering came when stupid Sears wanted $13! for this seal, which would
have failed, too! Larry loves to tinker with things that don't work. I
took a piece of 1/4" surgical hose and cut it a little too long to fit
around the groove of the top. Initially I used piano wire inside the hose
to hold it in place permanently. Then, I noticed the air in the hose
expanded with the heat, making the seal REALLY tight...steam tight! I
dumped the wire and used a small nipple of nylon tubing inside the ends of
the rubber to seal the pressurized air inside the hose, so it couldn't
escape and cause the hose to collapse when it cooled. As the pot heats,
the air in the hose expands the hose. When the pot is boiling, you have to
pull REALLY hard to get the top off....problem solved! Waterwise never
gave me even a free carafe for my trouble....(d^

Well, that should give you some ideas. After you've made a still, don't
tell anyone about it. You'll have to hear all the alcohol still jokes if
you do....(c;

Exotic biology doesn't do well in steam, like it does flowing through an RO
membrane. The water makes superb coffee and drinks. If the container is
properly sanitized, the water can be stored for years as it remains pure.
NOTHING in tap water or spring water is useful to your body. I started all
this because the elemental calcium in our water, here, caused many kidney
stones I found quite painful. NO MORE! The iron, calcium, and other
metals in water are NOT useful to your health. They are elemental,
dissolved metals, not biologicals you use to make bones/teeth/etc. The
sales crap in all this filtering and RO systems is a pack of awful lies....
Filter your water and take it to a lab. Read the report. The big pot's
remaining, trapped stuff looks like sewage and stinks awful after I've
boiled off 20 gallons of water from it. I can't believe city water is safe
to drink. The calcium deposits look like seashells!

--
Larry