Some here may have read my posts about reverse osmosis. This a continuation of them.

Tonight we decided to find out how low of a head pressure [differential pressure between the inlet and outlet of the filter] that we could get a reverse osmosis filter to operate.

The setup was kept basic so anyone can repeat the experiment in a few minutes.

Basically a water supply bottle was placed on the top shelf of a kitchen cabinet, the RO filter on the counter and a measuring cup on the floor to collect the purified water.

I left a solids filter and a carbon filter in the input side of the RO cartridge and a carbon filter in the output to simulate a near worst case resistance to flow.

Tubing was dipped into the supply bottle placed up high in the cabinet and fed the filter setup. Another piece of tubing went from the filter output down to the measuring cup.

The waste tubing was pinched nearly shut w/ visegrips.

The supply bottle was filled and the system purged by sucking on both the waste and output tubing. It is sort of hard to get the flow purged and started by mouth suction alone but I did it suckcessfully several times. A small squeeze bulb or pump would make things a lot easier.

After the filter and lines were purged, the waste line started dripping pretty fast as was expected. It was clamped off so that a drop came from it every 5 seconds or so.

The output [pure water] side started to drip slowly, a drop or 2 a second or so. That was surprising considering the filter components in the system and the very low head pressure/suction pressure of ~2 or 3 PSI.

An interesting thing was the change in flow with a small change in the elevation of the supply bottle. A 12" increase in height seemed to nearly double the output flow.

The output flow dripped about 1 to almost 3 times a second depending on the height of the supply bottle.

In about 10 minutes I collected four ounces of pure water so I figure even a minimal setup like this with no pressure other than that created by 6 feet of elevation could provide plenty of drinking water for several people and enough for cooking, brushing teeth, etc.

I bought this setup on eBay for about $40 and all the components are connected by simple quick connects and it can be taken apart or reconfigured in seconds.

A setup like this could probably take water from a septic tank or urine and make it drinkable.

This is important info and could make your situation a lot better or even save your life.

RO filters are all over the place and could be "salvaged" from under a sink and put to work like this.


They are cheap and readily available ––-for now...

Take some pics brother, we or atleast I would be interested in seeing the setup.
Thanks rooster

Originally Posted By rusteerooster: Take some pics brother, we or atleast I would be interested in seeing the setup. Thanks rooster

Can't take pix [don't know how to post] but will answer any questions so you can understand the setup.

IM inbound with questions.

Link to the Ebay components?

Good writeup.

Thanks,

Merlin

Update: Last night after I wrote this I found a way to increase the flow rate without changing the height of the water supply.

By putting a "U" in the last 2 inches or so of the outlet tubing where pure water is discharged into the measuring cup, it seems that the exit tube effectively stays 'filled' contributing more to the differential pressure of the system.

The flow really increased to maybe three times the rate or maybe a quart or more per hour.

Of course, our setup as pretty much worst case, and anyone can come up with a 10 or more foot differential between supply and discharge, even in the woods.

With this setup we can make lots of 'pure' water anywhere without much intervention.

Originally Posted By Merlin: Link to the Ebay components? Good writeup. Thanks, Merlin

Here's a general link to components on eBay and you can learn a lot by reading about them.

search.ebay.com/reverse-osmosis

This RO system is similar to the one I'm using, it weighs about 4 pounds and fits into a small gym bag. You can hook it to your sink and be making purified water in seconds to begin understanding how to use it for a BO or SHTF:




Note the tubing is 1/4 inch and is either stiff or soft and flexible. The connectors are simple quick connects that release by pressing on a small ring. Reconfiguring a setup takes just seconds.

If you scroll down this last link you will also see UVC ultraviolet 'sterilizers' that are cheap and good quality. Running water through one does the same thing as a SteriPen, but is a lot more powerful. You can process water much faster through a UVC 'filter' and power consumpion is very low, a relatively small battery can be used.

Sort of like a Coleman flourscent lantern except the tube puts out UVC light and the tube is in a housing so water can pass over it. A gallon can be treated in a few minutes and the light turned off saving electricity.  

The supplied ballast runs on 12VDC IIRC. I have several in my preps plus spare tubes and the stuff to make more. The weight is trivial compared to the water they can process.

-Eating my raw oatmeal and washing it down with RO water.

TDS inline meter. Really like them!




search.ebay.com/search/search.dll?sofocus=unknown&sbrftog=1&from=R10&satitle=reverse+osmosis+tds&sacat=-1%26catref%3DC6&saprclo=&saprchi=&sargn=-1%26saslc%3D2&sadis=200&fpos=81501&sabfmts=1&ftrt=1&ftrv=1&fsop=2%26fsoo%3D2&fgtp=



Ultraviolet water sterilizers, click to links on pg to learn more.

search.ebay.com/search/search.dll?sofocus=bs&sbrftog=1&from=R10&_trksid=m37&satitle=UVC++water&sacat=-1%26catref%3DC6&saprclo=&saprchi=&sargn=-1%26saslc%3D2&sadis=200&fpos=81501&sabfmts=1&ftrt=1&ftrv=1&fsop=2%26fsoo%3D2


search.ebay.com/search/search.dll?sofocus=bs&sbrftog=1&catref=C6&from=R10&_trksid=m37&satitle=ultravio*+water&sacat=-1%26catref%3DC6&saprclo=&saprchi=&sargn=-1%26saslc%3D2&sadis=200&fpos=81501&sabfmts=1&ftrt=1&ftrv=1&fsop=2%26fsoo%3D2&fgtp=



Here's my UV sterilizer. Cost about $40. Incredible price for the quality. It can run on batteries if you know how and uses very little power vs quanity of water sterilized.  Probably isn't needed unless your stream/water source is infected w/ viri. Like in a BF pandemic. But get a couple anyway.



Includes:

UV Housing with 1/4 inch quick connect fittings

UV Lamp

Stainless Steel sleeve

120 V/60 Hz Ballast

Specifications:

Flow Rate                                    1 gallon per minute

UV Output                                  253.7 nm

Lamp Current                             0.162 A

Max. Pressure                             120 psi

Max. Temperature                      104 F

Size                                             1.9 x 11 inch

EXPY37- Thanks for the info. I will try it out but I have one question. (Probably the first of many.) Considering that the main problem (as I have read) with rev. Osm, systems is the need for medium to high PSI levels just to get the water clear of the membrane. How does this accomplish this without a high output pump? Sorry about my ignorance on the subject as I just started my research but I'm very interested in it as I live by the Ocean and it could be very useful. Also, are the filters serviceable and if they are for how long. Ok so that was more than one question. Sorry.

Thank you Sir,

Riese

Originally Posted By riese: EXPY37- Thanks for the info. I will try it out but I have one question. (Probably the first of many.) Considering that the main problem (as I have read) with rev. Osm, systems is the need for medium to high PSI levels just to get the water clear of the membrane. How does this accomplish this without a high output pump? Sorry about my ignorance on the subject as I just started my research but I'm very interested in it as I live by the Ocean and it could be very useful. Also, are the filters serviceable and if they are for how long. Ok so that was more than one question. Sorry. Thank you Sir, Riese

I've been successful using low pressure at reduced output flow.

Life depends on how dirty the water is, replacements are relatively cheap and easy to change. Lower pressure might extend the life.

In any case life of the RO filter is probably way longer than most SHTF's will last.

Originally Posted By EXPY37: Originally Posted By rusteerooster: Take some pics brother, we or atleast I would be interested in seeing the setup. Thanks rooster Can't take pix [don't know how to post] but will answer any questions so you can understand the setup.

If you can take pics, you can email them to me at [email protected] and I will post them for you.

Originally Posted By colklink: Originally Posted By EXPY37: Originally Posted By rusteerooster: Take some pics brother, we or atleast I would be interested in seeing the setup. Thanks rooster Can't take pix [don't know how to post] but will answer any questions so you can understand the setup. If you can take pics, you can email them to me at [email protected] and I will post them for you.

We're on the left coast now but if there is time when we get to where the filters are I will.

I have sold and installed RO systems for a small water treatment company.  Iam not
an expert but do know that there needs to be pressure for optimal out put.  Take
your standard pressure tank out of the equation and even household pressure dwindles
the output.  I would be interested in pictures of your experiments and test of your output
water.  Do you have a TDS meter to test your output.  Also clamping off your wastewater
output leaves your waste water in your membrane housing which will contaminate your RO water.

I have tried to replicate a pressure vessel that can be pressurized with a bicycle pump but
my experiements have yet to produce.  My time has been spent else where.  Need to dust
of my experiments and get back to it.  I have a Bay of brackish water for the taking
should I need it.

I've lived with a low (7 psi ) ro system  since 1998 or so, they are designed to be self cleaning by self flushing the input constantly, this is not feasible for te rain water collector or the bucket collector as 99% of the water is wasted.
You must block the waste tube to reserve your water supply. It is also important to feed only clean water into the unit, they will clog with junk if you don't back flush and rinse periodically.

Use the cleanest water you can, it is also a good idea to use the accumulator tank to provide a back-flow pressure to force particals back through the unit once a week or so ( to keep the pores clean) .

after five years it still worked fine for 1 .25 people, now that there are two people it is not adequate. the fix is to increase pressure or replace it.

My rain water settles in 55 gal blue barrels so it is fairly particulate and mineral free, YMMV.  

Originally Posted By fire_medic: I have sold and installed RO systems for a small water treatment company.  Iam not an expert but do know that there needs to be pressure for optimal out put.  Take your standard pressure tank out of the equation and even household pressure dwindles the output.  I would be interested in pictures of your experiments and test of your output water.  Do you have a TDS meter to test your output.  Also clamping off your wastewater output leaves your waste water in your membrane housing which will contaminate your RO water. I have tried to replicate a pressure vessel that can be pressurized with a bicycle pump but my experiements have yet to produce.  My time has been spent else where.  Need to dust of my experiments and get back to it.  I have a Bay of brackish water for the taking should I need it.

"Optimal output" is of no concern in my SHTF application. As long as I can supply my BO location with enough to drink, etc, on a daily basis I'm GTG. It's not like it's providing water for a whole house.

Yes, ref the TDS probe. Have several, and they are cheap on eBay. The are several ones that go in-line with source and output , mine cost about $20 IIRC.

The water tested as if it were passed thru a RO filter. As my OP said, the processed volume was low due to the low differential pressure. The flow increased "exponetially" when the pressure was increased by raising the water supply elevation.

My needs for pure water are modest and I would also have a far greater elevation [pressure] differential that the experiment above. I used that elevation as a starting point to see if it would work.

The RO 'waste' outlet was not completely shut, just restricted more than normal to conserve water.

Which has me thinking. Maybe the 'waste' port could be pulsed every minute or so to accomplich the purging but conserve water.

My application is to purify water where there is an extreme shortage of it. Unlike most who have rainwater, a creek, or well available.

And the waste can be reprocessed or otherwise used, it won't be 'wasted'.

Originally Posted By LadyMacBeth: I've lived with a low (7 psi ) ro system  since 1998 or so, they are designed to be self cleaning by self flushing the input constantly, this is not feasible for te rain water collector or the bucket collector as 99% of the water is wasted. You must block the waste tube to reserve your water supply. It is also important to feed only clean water into the unit, they will clog with junk if you don't back flush and rinse periodically. Use the cleanest water you can, it is also a good idea to use the accumulator tank to provide a back-flow pressure to force particals back through the unit once a week or so ( to keep the pores clean) . after five years it still worked fine for 1 .25 people, now that there are two people it is not adequate. the fix is to increase pressure or replace it. My rain water settles in 55 gal blue barrels so it is fairly particulate and mineral free, YMMV.

Do you keep your waste port blocked most of the time? Aside from periodic flushings.

In a BO where I had limited ability to carry material I'd consider using a MSR hiking filter to reverse flush the RO filter once in a while.

Replace the filter, they are cheap. ~$20 on eBay.

Here's a portable system similar to the ones I bought a year + ago. Maybe the same one. My SO is in charge of using it now. It sits on the kitchen counter with the input connected to the faucet as shown in the auction below and the output line is directed into the container we want to fill. We keep the container in the sink so when she forgets to turn it off it doesn't flood the floor.

cgi.ebay.com/125-GPD-Reverse-Osmosis-RO-membrane-Water-Filter-Reef_W0QQitemZ160112560098QQcategoryZ20684QQcmdZViewItem



It weighs 4 pounds, will fit into a small gym bag, costs $40, and will process more H20 than you will ever drink in many years.

You can accessorize it with a TDS tester inline or separate, adjustable 'waste' valve, etc.

Features: Uses with this item
Want pure water immediately, this does the fastest one for all portable units
Use most reliable name brand TFC (made in U.S.A.) Reverse Osmosis membrane
High technology to deliver the greatest quality water you deserve
Perfect for apartment, RV's, business travel, vacation, yacht, boat, Mobil home or anywhere you need the pure water
Just turn the valves on and you have pure water
Comes with an adaptor that will fits most sink faucet Conveniently, easily, directly
Easy to install this system, just like replacing a kitchen faucet
Easy to place on counter top, the sink or anywhere you want
No more bottles of water to carry home
Removes 99% of all Sodium, aluminum, lead, copper, arsenic, mercury, calcium, phosphate, iron, magnesium, zinc, chloride
, nitrate, silicate, cyanide, sulphide, nickel, silver, bicarbonate, manganese, ammonium, barium, chromium and Phosphates
Removes 99% of all bacteria from your water
Water Purity Reference: (1.)Tap or well water(200~400 PPM), (2.)After RO system(1~20 PPM)
This system will start to generate the pure water under 35 PSI, please make sure if the pressure of your tap/well water is enough

.

Here's info on the press in/pull out to release John Guest fittings used with RO systems.

!/4 inch tubing available from any hdwr store, fun to work with, link.

Wow, this is a great link for fittings to see what's available.

www.waterfilterstore.net/fittings_valves_and_tubing.asp?gclid=CO-0kpiX948CFRogYQodNiiZ1A



And how they're used.

I installed a valve on the waste out flow, in the morning when the accumulator is full I turn off the water supply and open the waste valve for half an hour, the accumulator puts -pressure on the membrane to loosen particulates, then I turn on the water supply and let it flush for 5 min or so.

Originally Posted By LadyMacBeth: I installed a valve on the waste out flow, in the morning when the accumulator is full I turn off the water supply and open the waste valve for half an hour, the accumulator puts -pressure on the membrane to loosen particulates, then I turn on the water supply and let it flush for 5 min or so.

OK, so you don't let any waste flow except when you back flush. That's good info.

For a BO, my water is scarce [that works for me by the location being undesirable] and every bit has to be used. Plus the accumulator tank is too heavy to carry so I think a reverse pump with the hiking filter every day or so will work. Maybe if I can get enough head pressure by raising a juck 20 feet or so would do it, maybe add a little chlorine to the flush water too.

Hey, it's nice to find someone who thinks like I do about this stuff!

you can still use the flush water for cooking if your supply is very low.

please describe the procedure you use to flush the system.
Thanks, dont know how I missed this great thread.

that is really impressive

I have used RO systems before and really like them.  Thought they needed too much head pressure to work by gravity alone, but this really has me thinking (and looking at the pool in the backyard).  Good info, thanks.

[div class='quoteStyle']Originally Posted By rxdawg:
I have used RO systems before and really like them.  Thought they needed too much head pressure to work by gravity alone, but this really has me thinking (and looking at the pool in the backyard).  Good info, thanks.
Chlorine may or may notbe an ideal source of water. A creek or puddle might be better, I haven't tried pool water. IIRC there are reports of it working, worst case it shortens the life of your filter.

Filters are relatively inexpensive.

I don't plan on using pool water, I have to use a sort of brakish aria area water, so I'll clean it up with a deionizer before the RO filter.

.

Originally Posted By EXPY37: Chlorine may or may notbe an ideal source of water. A creek or puddle might be better, I haven't tried pool water. IIRC there are reports of it working, worst case it shortens the life of your filter. Filters are relatively inexpensive. I don't plan on using pool water, I have to use a sort of brakish aria area water, so I'll clean it up with a deionizer before the RO filter. We use the little portable unit in the pix above at the sink in CO. No tank, just fill up a container and put them on the shelf or fridge. My SO is trained so I don't get involved anymore on the day to day ops. It has cut our bottled water bill down mucho. The water tastes great, she learns how to process it in prep for any SHTF and I supervise.

Carbon block prefilters are cheap and usually handle chlorine without much problem.  I used a RO system on south GA shallow well water that smelled like King Kong farted in it, and it came out better than any bottled water you could buy.  Had to change prefilters like crazy due to the sediment but the membrane never died.

I am thinking extended event, after exhausting my stored water.  Having 13,000 gallons sitting outside that I can purify via gravity beats using a handheld filter and nalgene bottle.

Originally Posted By rxdawg: Originally Posted By EXPY37: Chlorine may or may notbe an ideal source of water. A creek or puddle might be better, I haven't tried pool water. IIRC there are reports of it working, worst case it shortens the life of your filter. Filters are relatively inexpensive. I don't plan on using pool water, I have to use a sort of brakish aria area water, so I'll clean it up with a deionizer before the RO filter. We use the little portable unit in the pix above at the sink in CO. No tank, just fill up a container and put them on the shelf or fridge. My SO is trained so I don't get involved anymore on the day to day ops. It has cut our bottled water bill down mucho. The water tastes great, she learns how to process it in prep for any SHTF and I supervise. Carbon block prefilters are cheap and usually handle chlorine without much problem.  I used a RO system on south GA shallow well water that smelled like King Kong farted in it, and it came out better than any bottled water you could buy.  Had to change prefilters like crazy due to the sediment but the membrane never died. I am thinking extended event, after exhausting my stored water.  Having 13,000 gallons sitting outside that I can purify via gravity beats using a handheld filter and nalgene bottle.

Thanks for the suggestion! And the prefilters are cheap.

I cant find any simular units up on ebay right now.  Does anyone sell one ready to go?

Originally Posted By Granola: I cant find any simular units up on ebay right now.  Does anyone sell one ready to go?

Are you spelling RO correctly, they're all over the place, like here.

$35 bucks! Cheaper than a hiking filter.Who here will invest in one? One or 2 people?

cgi.ebay.com/New-Portable-4st-100GPD-Reverse-Osmosis-RO-Water-Filter_W0QQitemZ110222661790QQihZ001QQcategoryZ20684QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Originally Posted By EXPY37: Originally Posted By Granola: I cant find any simular units up on ebay right now.  Does anyone sell one ready to go? Are you spelling RO correctly, they're all over the place, like here. $35 bucks! Cheaper than a hiking filter.Who here will invest in one? One or 2 people? cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=120188361612&ssPageName=STRK:MEWA:IT&ih=002

Man I suck at the internet today.  Thanks!

Bumped for another topic.

Originally Posted By EXPY37: The output flow dripped about 1 to almost 3 times a second depending on the height of the supply bottle.

How is this set up? Similar to an IV drip? (bottle filled, turned upside down and let gravity take its course)

Is it just me or is this $35 filter really $85 delivered The buy it now link is $49.99 but the ad copy still says its "buy it now for $34.99"

Not saying its a bad product or even a bad deal...just hate "loaded" S&H charges like that.

Keeping on the constructive side of things - I do have a question. What "input adapter device" are you using? they list three different options and it seems the garden hose adapter may be the most useful since that easily fits faucets (with a cheap adapter), clothes washing machine hoses (direct connect/same threads) and of course..wait for it..garden hoses.

I like the idea and just may pick one up for testing. Seems like this would be a nice complement to a stealth trailer electrical set up for semi portable RO on the go

ETA - I still need to revise the schematic in the other thread...

Originally Posted By ROMAD-556: Is it just me or is this $35 filter really $85 delivered The buy it now link is $49.99 but the ad copy still says its "buy it now for $34.99" Not saying its a bad product or even a bad deal...just hate "loaded" S&H charges like that. Keeping on the constructive side of things - I do have a question. What "input adapter device" are you using? they list three different options and it seems the garden hose adapter may be the most useful since that easily fits faucets (with a cheap adapter), clothes washing machine hoses (direct connect/same threads) and of course..wait for it..garden hoses. I like the idea and just may pick one up for testing. Seems like this would be a nice complement to a stealth trailer electrical set up for semi portable RO on the go ETA - I still need to revise the schematic in the other thread...

Yep, the big shipping charges tick me off too. But the guy has good positive feedback and I haven't been able to find compact RO systems any cheaper than his lately. I did update the link yesterday and I saw the price did go up, maybe all the AR15 guys are driving the price.

As far as how to connect it, go to HD or Lowes and look at the plastic 1/4 inch tube fittings and there are almost infinite options to connect.

IIRC, the faucet adapter comes w/ it. My SO is in charge of making water and that's how I hooked it up for her.

I am considering putting one in the ST so we don't have to buy bottled water all the time. Front and center up high inside roof is where it seems to want to go. Or tucked away in the bathroom.

The price went up to $49 on these UV purifiers since I stocked up but I think they would be useful in a flu pandemic or where you need to deal with pathogens in water and do it fast with little consumed energy. They are a deal pricewise.

i7.ebayimg.com/02/i/000/8e/7d/f4d4_1_b.JPG

tag to read later

get an aquarium mag. It has all of the RO and UV systems you could want.

Bump to link from another thread.

Bump per request.

bump to answer questions w/out spending an hour recomposiing.

Anyone putting together an RO system for SHTF?

Any other sources than Egay for this stuff? As in legit companies.

Hi EXPY37,
I have the same unit stored at the ranch. I unclipped the filters from one another and slid the unit down inside of a 3.5 gallon Spray Doc.(pump up sprayer) I'm of the understanding that the membrane operates better under pressure. My theory is that several pounds of pressure would be better than a gravity feed. I may be totally wrong. The Spray Doc also allow for faster filtered water production.

I need to look into the UV lamp setup, Thanks for the info

Just my solution
Ron

Billclo,

the companies on eBay are probably more customer sensitive than some box stores. That said, Sam's was dumping inventory and had the standard undercounter RO systems with faucet and tank for less than $100 IIRC before Christmas and I stocked up and posted about it here.

Any box hardware store will have them but the cost will be greater. Don't buy one of the GE or whatever gay systems with all the filters 'integrated' so you can't get to the hoses and reconfigure the system, once you are familiar with the process, which is intimidating at first but a lot easier than taking apart an AR once you get the hang of it.

Also, eBay will have at VERY good prices all the parts and pieces to customize your system for survival/portable use if you do a little research. Like TDS meters,hose, valves, etc. Open a PayPal acct and you click on a part and pay for it and pick it up at your door a couple days later. There is a lot of Buy-It-Now so you don't have to wait for an auction to come up.

Also I have found after getting great deals and selection of products of all kinds from ATV to XYZ on eBay, stuff that I couldn't easily have gotten elsewhere, it hasn't hurt me or turned me gay, at least not that I've noticed -yet.  

Try it and if you get hair on your hands or something give us a heads up.



Arpaul,

using a pressure sprayer should work OK [haven't tried it and don't know the pressure, if you have one of the big white plastic tanks with the 12 volt pump on it that should be great], also an RV 12 VDC pump would work great, but elevating a container high up on something on your ranch should still be the easiest for you.

That's why water towers were invented...

One last thing that is REAL important.

If you are using the RO system with a tank-

[I have always NOT used the tank and the included faucet for pemanent applications since I ususlly install the RO filter in a utility area and my SO just turns it on when she wants to fill our everyday water bottles, maybe twice a week.

I put a nice easy to turn 1/4 or 3/8 inch stainless ball valve on the water supply to feed the RO system and a piece of 1/4 FLEXIBLE tubing like silicone from a hobby shop on the RO output for her to stick into whatever she is filling up]


-back to the tank, it can be useful as an "accumulator" or 'storage buffer' on the INPUT side of the RO filter, just like the function of a pressure tank on a water well.

That's because the tank has a rubber diaphram dividing it into 2 chambers.

In an extreme example of how you could get pressurized water [remember you only need say 10 pounds to make it work] you can fill a gallon of water into one side of the RO tank and use a tire pump or whatever to pressurize it and the 'accumulator' function will keep up the pressure and the RO filter filtering while you go do something else like shoot Zombies.

Lots of other ways to use it too, just use your engineering imagination.

A few pressure gauges and an assortment of fittings are great to have around. I used to keep Home D in biz by buying all kinds of brass and plastic fittings.




Study the main part of this thread to build up your knowledge on the parts and pieces and don't let your fear of eGay cause you to loose opportunities.

Here's another idea, I noticed a hand held pressure sprayer the other day at one of the box hardware stores that has a pump that runs on batteries.

It looks like it could pressurize the RO accumulator tank [described above] real well to make a VERY NICE self contained water system for a camp or house if there was no power.

Sort of like a hands free version of what ArPaul is doing on his ranch with a sprayer.

"Billclo,

the companies on eBay are probably more customer sensitive than some box stores. That said, Sam's was dumping inventory and had the standard undercounter RO systems with faucet and tank for less than $100 IIRC before Christmas and I stocked up and posted about it here.

Any box hardware store will have them but the cost will be greater. Don't buy one of the GE or whatever gay systems with all the filters 'integrated' so you can't get to the hoses and reconfigure the system, once you are familiar with the process, which is intimidating at first but a lot easier than taking apart an AR once you get the hang of it.

Also, eBay will have at VERY good prices all the parts and pieces to customize your system for survival/portable use if you do a little research. Like TDS meters,hose, valves, etc. Open a PayPal acct and you click on a part and pay for it and pick it up at your door a couple days later. There is a lot of Buy-It-Now so you don't have to wait for an auction to come up.

Also I have found after getting great deals and selection of products of all kinds from ATV to XYZ on eBay, stuff that I couldn't easily have gotten elsewhere, it hasn't hurt me or turned me gay, at least not that I've noticed -yet.

Try it and if you get hair on your hands or something give us a heads up. "

The reason I don't use Ebay is that I've been ripped off a couple times, and their new rules suck. As a seller I got tired of over 50% bailing after making the winning bid and Ebay didn't give a hoot.

I don't use PayPal because they really stuck it to me - held $1000 for 6 months for "investigation" of a sale they didn't like because it was gun-related, despite it being 100% legal.

If the old links in this thread's body don't work anymore let me know or just do a general search for the key words on eBay.

Stuff should be coming down in price because of the economic situation we are having.

Here's an illustrative diagram relating particle size to various common materials. Note the bottom scale is conveniently defined in microns, directly relating to measurements we're already familiar with ––for hiking, Berky, ceramic, the new Sawyer filters, reverse osmosis, etc.







Note that the RO filter is on the far left of the chart and the far right relates to coarse sand as a filter media. A pin "point is about 80 microns and viruses can to be as small as .002 microns according to the chart. An RO filter pore diameter approches the the radius of an atom. Pretty danged small.

A sugar molecule is at the limit of being passed by an RO membrane, of which there are several kinds of membranes designed for different applications.

Processing brackish water requires pressures around 350 psi for efficient flow because of the type of membrane used, non-brackish water can be processed at around 40 psi, and as I have reported, at a considerably lower pressure albeit with much less flow.

Interestingly, the hollow fiber filter membrane that is used in the new hi perf Sawyer filter, being discussed in another thread, appears to be another form of a reverse osmosis 'membrane'.

The 10 inch standard RO membrane cartridge used in household RO installations can be purchased in various flow rates and in several materials depending on your specific application. They are available in 20 inch and larger sizes for institutional use.

Here's one similar to the one we're using at our location, it has a pore size of .001 microns [not too much smaller than the high performance Sawyer hollow fiber filter and it's designed to be tolerent to chlorine.] Note that the price is a complete ripoff for uninformed consumers.

http://www.advancedwaterfilters.com/filter-products/reverse-osmosis-membrane-cta.html

This chart is handy to print out and refer to in discussions of different kinds of filters especially when making a decision which is best for your needs.

Temperature of the membrane is directly related to the flow efficiency.

Also note the difference between "suspended" contaminants and "dissolved" contaminents. Dissolved contaminants won't be filtered out by ceramic and larger pore sized filters. Generally you have to use RO to remove dissolved substances at the atomic/molecular level.

A carbon block filter inline to other stages works well to adsorb some dissolved materials.

ETA One last issue.

There are reports of bacteria being able to "grow through" the pores of RO and other small pore filters. Filters that are used occasionally seem to have the problem, filters that are in constant use are reported to be less susceptible. Chlorine treatment of the input supposedly kills the bacteria.

Dunno if anyone's said it yet, but increasing the water supply's elevation by 1 foot increases the differential pressure by 62.4 psf (0.433 psi).

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