Reverse osmosis unit anyone here use one

pete · Post by **pete** » 11 Nov 2003, 12:50

Am thinking of getting one as I have trouble collecting enough rainwater for 3 tanks.
Does anyone have any basic info on them like how do you know when to change the carbon prefilter and how long do the filters and membranes last
I dont use tapwater as they add chloramine where I live
thanks
pete

Caol_ila · Post by **Caol_ila** » 11 Nov 2003, 13:01

Hi!

I just recently bought one on ebay for 25 euros. It can do around 100 litres a day. The downside is the ratio of 1/~4 meaning if you dont have a cistern or other reservoir you waste a LOT of water. Im just using it for my L15 breeding Setup and cooking.
Mine doesnt have a carbon filter i think (not really sure) but i was told the membrane holds up to 6 years depending on how often you rinse it.
The ro water i get is kh <1Â° gh <1Â° from 10Â°/18Â° tapwater. for the clorine i cant tell cauz its only added here in cases of emergency and thats very seldom.
From a ecological standpoint this thing is an absolute nono.
greetings
C

flyinmike · Post by **flyinmike** » 11 Nov 2003, 13:39

You definitely need something to catch the overflow in. Like C said, for every one gal. of filtered water about 3-4 goes out the door.

The ro water i get is kh <1Â° gh <1Â° from 10Â°/18Â° tapwater.

Wow, my R/O comes out 0Â° & 0Â° with a pH of 5.8 (no buffers left to keep it up). I then use baking soda to raise the KH to 2Â° which brings my pH up to about 6.4..
Definitely check the pH of your water before you use it!

Remember too, when you are using R/O you are taking out the good as well as the bad. You need to add something back in. I use Tetra Blackwater extract and Florapride.

Caol_ila · Post by **Caol_ila** » 11 Nov 2003, 14:01

Hi!

The kh <1Â° gh <1Â° actually means that i cant measure how much conductivity it has the tests change color on the first drop. So it could well be 0/0 although afaik all RE work at 95% efectivity which means it cant be 0/0. The manual says re water will be around 30-50 ÂµS.
If you catch the overflow the question is what to do with it? I cant store 300 litres of water in my appartement.
greetings
C

RogerMcAllen · Post by **RogerMcAllen** » 11 Nov 2003, 16:09

Use it for anything you want. Water plants, do laundry, take showers, even drink it. It isn't so much bad water as it is simply not RO water.

Caol_ila · Post by **Caol_ila** » 11 Nov 2003, 16:18

hmm my appartement has 29 squaremeters...dunno how many plants you got at home...;) and im not sure the orchids would be very happy about 50Â°gh water. And i use the ro water for tea and coffee as the tap water tastes awfull and i cant imagine that harder water would be better. hmm i wonder how i could use the water to shower...maybe for taking a bath but then again its cold.

Caol_ila · Post by **Caol_ila** » 11 Nov 2003, 16:23

Another thing that just came to my mind...if u use it for laundry (if you have a laundry machine as i dont have one) you will surely (im no expert here) have to use huge amounts of washingpowder and antical salts and the machine wont be very happy about it...

angel · Post by **angel** » 11 Nov 2003, 16:59

You could try a deionising unit which wastes no water. They don't last as long as an RO unit but gives water of comparable purity. Another plus is that they are much cheaper. I use one to make up water for a marine aquarium and it works fine.

It you are going to buy a RO unit make sure it has an effective pre-filter. They are cheaper without but the membrane clogs very easily and has to be replaced on a regular basis.

Hope this helps

Caol_ila · Post by **Caol_ila** » 11 Nov 2003, 17:07

Hi!

deionising unit

but you have to regenerate it once in a while dont you? Ergo if you have very hard water the more often youll have to regenerate...handling acids isnt everyones thing.

Post by **Barbie** » 11 Nov 2003, 17:57

I haven't hooked my RO unit up at this house yet, but I will be by next summer. I intend to plumb it so that the "excess" water runs out into the swimming pool, which is wasting gallons and gallons of water to evaporation, and where we have to add calcium to keep the pH up anyway. It should work a treat. At least that 4 or 5 months of the year anyway

The hot tub just doesn't use enough water to make it feasible to use for it.

On another note, rather than adding soda to the water, you can always add back in a set amount of your waste water to bring the kH up to where you want it. It's usually quite easy to figure out just how much it will take to stabilize it, then use that same amount on your barrel of water every time. It worked great when I did it.

If your water is over 5 degrees kH, the resins in the DI units are rapidly depleted, like in 200 gallons or less. I'm not personally comfortable enough working with strong acids to make that something I want to mess around with. I'll acclimate them to my tap water first and do without fry.

Barbie

Post by **Janne** » 11 Nov 2003, 20:47

The ro water i get is kh <1Â° gh <1Â° from 10Â°/18Â° tapwater.

Thats lots of calcium in your tapwater and that will clog your membrane in the RO unit very easily, if you cant take that away before the RO you can rinse the membrane with kaustiksoda (hope it's the same in english) once in a while if you use a prefilter that you fill with water and soda and let the RO runs thrue the membrane, after you have to let the RO run for a while until all the soda is gone.

Wow, my R/O comes out 0Â° & 0Â° with a pH of 5.8 (no buffers left to keep it up).

Normally the pH should be neutral and 7.0 after the RO unit, in other cases your tapwater must contains acids mostly from humus.

Janne

magnum4 · Post by **magnum4** » 11 Nov 2003, 21:04

you can find some information here:
http://www.kentmarine.com/html/fullsizero.html

when to change the carbon prefilter and how long do the filters and membranes last

Depends which model you choose, this is the main reason to get a full size RO unit.

My RO unit gets replacement TFC, micron and carbon every 3,750ish gallons.

Deionization is on a seperate link which i only use to produce water for marine tanks because it only treats 400 gallons, replacement cartrage cost Â£30 rrp.

what does the unit need to produce each day to suit your needs, also you mention chloramine in you tap water, have you any idea of the level?

Post by **Barbie** » 11 Nov 2003, 22:00

Actually, the pH of your RO water will depend on what the pH went into the unit at. You remove the ability of the water to have a stable pH, but it takes some sort of waste or CO2 or something of the sort to start the pH on its downward spiral. Mine would regularly come out of the RO at 7.8, but would be down to 6.8 overnight in a 40 gallon barrel with 1/4 teaspoon of acid buffer.

Barbie

flyinmike · Post by **flyinmike** » 12 Nov 2003, 00:09

Janne wrote:Normally the pH should be neutral and 7.0 after the RO unit, in other cases your tapwater must contains acids mostly from humus.

Janne

The following is a short quote from a permanent post on fishgeeks.com by katestjohn:

"RO water often is not 7.0 when pulled from an RO unit, and actually can be quite startlingly acidic. This is because of the 'tightness' of the membrane. The electrons can actually be stripped off the water molecule, leading to a net 'H+' charge: acidity."

Click here to see the full post:

http://fishgeeks.com/index.php?name=PNp ... ic&t=10784

It is well worth the read.

Post by **Janne** » 12 Nov 2003, 20:08

"RO water often is not 7.0 when pulled from an RO unit, and actually can be quite startlingly acidic. This is because of the 'tightness' of the membrane. The electrons can actually be stripped off the water molecule, leading to a net 'H+' charge: acidity."

Don't agree, you will not split the H2O molekyle in the membrane...but if the water you use contains organics acids the pH can be lower(electrones both H+/H- past the membrane) and you maybe need a carbon filter before the RO, but if the water not contains any kind of acid or carbonate the electrones H+ and H- will be equal and the pH will be 7.0 and neutral.

Mine would regularly come out of the RO at 7.8,

If the RO-unit and the membrane are of good quality the conductivity will be between 0-10 ÂµS and does not contains any carbonates and the pH will be 7.0 or lower.
Maybe if the pH in your tapwater are over 8.3 and it's not the carbonates that buffer the water the pH could be higher then 7.0 or if the water contains gasses but they leave the water very fast and if you use some air in the tank with the RO water they will leave faster and the pH should be 7.0 or lower after 24 hours, depending of your tapwater quality.

Janne

magnum4 · Post by **magnum4** » 12 Nov 2003, 22:40

Don't agree, you will not split the H2O molekyle in the membrane...but if the water you use contains organics acids the pH can be lower(electrones both H+/H- past the membrane) and you maybe need a carbon filter before the RO, but if the water not contains any kind of acid or carbonate the electrones H+ and H- will be equal and the pH will be 7.0 and neutral.

Janne tell this to katestjohn as i'm sure she will want to know, i would argue because mine comes out at about ph 6.2, but kate will explain not shout.

Post by **Janne** » 13 Nov 2003, 20:25

Not my intention to shout?...sorry if you feel like that.
Maybe my explenation not are so good but my english is not enough either to explain in a good way. But in your case with a pH at 6.2 for exampel your water must contains organic acids with lots of H+ or lots of Co2 are relaesed from the carbonates if you have a high kH level but that will leave the water very fast after a short while and I think I explain that before. The membrane for RO use are not tight enough to split the molekyle and if it was there would not come any water from the other side of the membrane, next step to make the water even more pure is to use a special membrane that only let the H2O molekyle past thrue and nothing else's after a RO unit...dont know the name for that filter in english right now but the techniqe is to use electric charged ion's on one side of the membrane like a battery that will drag all the rest of the electrones from the water and the H2O molekyle will be pass thrue the membrane under high pressure and absolutely pure water have a resistance of 18.3 Mohm after that the molekyle would be split. Maybe not exactly a right description but I do my best

Janne