# using reverse osmosis RO



## Andrew Butler (18 Jan 2017)

I'm curious as to the consequence of using RO water alone, if not why not and how to avoid using tap water


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## ian_m (18 Jan 2017)

People use RO water along with remineralising salts (or cutting with tap water) to get 100% known values of hardness and mineral content.

If you are in a hard water area you can use it to lower water hardness if breeding certain types of fish. Plants generally don't care too much about water hardness.

You must not use pure RO water as it has no buffering capacity (ability to resist pH change) and any acid or alkali present will cause instant pH changes (a pH crash) probably killing all your livestock.

RO water is not cheap, if on a water meter, and not very environmentally friendly. RO water wastes typically 5litres of water (maybe more, down the drain) for each litre produced (6 litre used in total). This works out 1.6p per litre RO for my Southern water. I would need 90litres per week for my tank, £1.44.

Most tap water in UK, along with suitable dechlorinator is perfectly fine for keeping plants.


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## roadmaster (18 Jan 2017)

Only fishes I am aware of that might fair well in straight R/O water is German blue Ram and possibly some of the appisto's.


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## Andrew Butler (19 Jan 2017)

ian_m said:


> if on a water meter



That's a big IF there!
There are units on the market which will preform 1:1 also which make it far more cost effective both on the wallet and environment.

I keep seeing people who have used pure RO with success which is why I question this, are they just lucky?


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## ian_m (19 Jan 2017)

Andrew Butler said:


> There are units on the market which will preform 1:


Where, never seen any in domestic settings. Even using an 8bar pump you will be lucky to get better than 3:1 waste:RO, generally much worse.To get greater usage you need much higher pressure eg 50bar as used in commercial desalination plants.

You must add buffer to RO water before use in a fish tank. Could of course be added by only changing 50% of tank water and having limestone/crushed shell in you tank to add hardness back. Pure RO water will very quickly kill fish and plants.


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## Andrew Butler (19 Jan 2017)

ian_m said:


> Where



There is a unit that vertex make, it's called something like vertex puratek deluxe; they claim 1:1.

I'm going to have a research on the buffer front unless anyone has any wisdom from experience to share?


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## ian_m (19 Jan 2017)

Andrew Butler said:


> There is a unit that vertex make, it's called something like vertex puratek deluxe; they claim 1:1.


They quote 1:1 on their web page, but 1:2.5 in the instruction manual.

The 1:2.5 is produced by the 8bar/110psi  pump (on 200 series) to match the rough 1:3 I quoted above. All RO membranes are the same, a fact of physics, to get less waste water you increase the incoming pressure. Well not quite true, there are some less efficient RO membranes (bigger molecular holes ?), I have seen 75% retention membranes (normal is 95% retention ie resulting RO water still has 5% salts level) but they are rare and tend to be specialised.

Shame the 200 model is over £400. Ouch.


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## KipperSarnie (19 Jan 2017)

30 years ago I lived in Lancashire, beautiful water.  Now back in Kent the water is very harsh, alkaline & hard!

I use RO water but have made a couple of alterations to my RO unit.

I have added another diaphragm in the waste line of the first diaphragm to scavenge a little more RO water.
I have fitted two taps to bypass the diaphragms so the water be filtered but not RO.
I then mix 50/50 for water changes.
I do add trace elements but about a third of the recommended dosage.  I found if I added more than that I had a build up of "Brown thread algae"  (Or what ever it's called)


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## Andrew Butler (19 Jan 2017)

ian_m said:


> They quote 1:1 on their web page, but 1:2.5 in the instruction manual


That's a bit naughty of them, I used to run the smaller 100 gpd unit, I did spend out as it was the only unit I could find at the time with auto flush and a pump, not only is my water hard as a rock but also very low pressure. Oh and I thought it performed a lot better than others on the market!  I did also add an additional DI chamber after the unit to polish it a bit more.



KipperSarnie said:


> I use RO water but have made a couple of alterations to my RO unit


1. If I'm honest I'm not understanding what you mean here!
2. Do you mean you have put a tee inline before the RO chamber so it just goes through the carbon, pre filter etc (unsure how many parts you have) - again I'm not fully understanding you here and how does this help the water?
3. I think I can understand this part! 

why do you still use trace elements if you have mixed your tap and RO water in proportion?
Which trace elements do you opt for?
sorry the questions- I'm sure a picture would paint a thousand words!


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## KipperSarnie (19 Jan 2017)

1.  In the waste water line going to drain I have added a 2nd diaphragm this then produces a little more RO water from what would be waste water.  More RO less waste.
The RO water produced from this diaphragm is "T'd" into the RO water line from the first diaphragm.

2.  After the Filters but before the Diaphragm I have put in a tap & "T" so the water bypasses the Diaphragm & goes straight to the delivery pipe.  To prevent any back flush of the Diaphragm  I have also put a tap & "T" in the delivery line so that the RO units are completely isolated when in that position, also to prevent the water passing the diaphragms when I want RO water.
(Believe me a picture would not help here!     trying to keep it compact it looks a  plumbing nightmare  )

As to your last question, call it *"Belt & Braces"*
I don't have a chemical break down of my tap water but I have an idea of what my fish require so just to make sure I add the trace elements.  At the moment I'm using Brightwell Discuscode.


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