# RO - How cheap and how to use?



## idris (9 Feb 2011)

I've long rulled out RO filters on grounds of cost, but I just stumbled across these
http://www.vyair.com/scripts/prodView.asp?idProduct=54
 and at only £46 I'm tempted.
*BUT* is there any *good *reason to go for something more expensive?

And I haven't really found anywhere that explains how to use one. 
So am I right in thinking that you have 3 pipes: one supply pipe, one filtered output and one waste output, with about half of the water that goes into the filter ending up as waste water?
IIRC I read ages ago that you have to have to keep the filter wet, or something like that? Is that wrong, or does it mater if you only need to produce 50L once a week and the filter is disconnected and sat in a cupboard for the rest of the time?


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## GHNelson (9 Feb 2011)

Hi
Its best if its attached to a cold feed mains pipe like the one that feeds your cold tap under your kitchen sink.
That's a good price for a RO unit they used to be about a £100.00 for a bare bones one about 5 years ago.
Their easy enough to install.
When not in use attach a 6mm push fit connector http://cgi.ebay.co.uk/6mm-6mm-Connector ... 439c984052
to the waste end and the RO water end of the tube this will keep your membrane wet.
Just detach and stick the waste tube down the sink and the RO tube with the connector in a container.
You may need one of these http://cgi.ebay.co.uk/Self-Piercing-Sad ... 3cb4d2b6a8
Sometimes they are supplied with the unit.
Anyway why do you want one?
Regards
hoggie


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## Ed Seeley (10 Feb 2011)

Go with a bigger one with the two clear containers below with a separate fine filter and carbon filter.  The only real cost of RO, apart from the water used, is the replacement filters every 6 months or so.  Also a really small RO unit will be very, very slow in producing water, a larger unit is quicker.  When I bought a 50gpd unit it was about £60.


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## Lisa_Perry75 (11 Feb 2011)

Out of interest why is it you want an RO machine?

Many members on here would say if it was solely for the purpose of planted tanks RO is an expensive waste of money.


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## mlgt (11 Feb 2011)

I have to agree on the aspect it wastes. But I would say the wastage comes from the creation of RO Water. 
If you compare say for instance distance travelled and price of RO water from LFS, it is actually cheaper in the long run to have a ro set up. 
Especially when you are keeping fish like say discus. It has its pros and cons, but many fishkeepers and planted scapists if given the choice would choose having an ro system. Thats from general conversation.

But they are unwilling to take on the additional work involved


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## idris (11 Feb 2011)

Thinking of getting one because I have _VERY_ hard water and I don't want to restrict the species of fish I can keep. It's not for a _solely_ planted tank. 
I think that unit does 50gpd and I'm not likely to want more than 100Lpw so the capaicty is fine. And the price is about half of one with 2 clear chambers. What advantage does that give me and is it worth doubling the price? 

The running costs appear to be negligable for the amount of water I need compared to the hassle of getting it from the LFS.


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## mlgt (11 Feb 2011)

If you have very hard water then as you said you are limited to the types of fish and plants you are able to keep.

Bearing in mind that a 50g produces about 10l a day depending on pressure. I would say go for the one you can afford the most. I am currently looking to purchase a 75g, but tempted to go 100g as I have a 350l tank. However I have discus and they appreciate good water conditions therefore I will aim to do a water change at least once every 10 days. I only have 2 discus currently. 

If you were to buy from a lfs, the cost will add up as you said. So its a no brainer that you should go for a bigger ro unit


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## idris (11 Feb 2011)

mlgt said:
			
		

> ... a 50g produces about 10l a day depending on pressure...


If my maths is correct that's about 20l of waste for 10l of purified water, right?
What happens if you run a 50gpw RO filter so that it produces 100 gallons of filtered water every week? What would happen if you only ran 50l through the filter each week? What limits it to 50gpw? 

As I'd expect to mix RO water with tap water, if I wanted to do 100lpw water changes, since my water is supposed to have about 350 mgl CaCO3, roughly what sort of percentage of RO water would I need for sensible water stats.

LondonDragon - not sure what point you're making. Sorry. I know they're all connected, but I'm concerned about hardness, not specifically pH. (Please don't hit me with too much chemistry.  )


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## mlgt (11 Feb 2011)

Dont quote me on it, but from what Ive read it is quite slow. Hence I am going for the 100gpd instead as it means I can fill up a 30l container during the hours I am at work. 

Where in Herts are you based? Im based in Barnet and havent tested the waters yet.


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## idris (11 Feb 2011)

30l while you're at work?    

I'm between Luton and St Albans. Our wter comes from the Lea which is chalk stream. I don't know where Barnet water comes from but your water supplier's website can almost certainly tell you.


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## mlgt (11 Feb 2011)

I was told that during the hours you are at work it can pretty much fill 30l. A1matt has the 50 or 75gpd ro set up and he told me you dont get that much, waste is what you get more of (lol)

However Im not on the water meter so therefore not fussed. I can also collect the waste to water my garden or wash my car.


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## Radik (11 Feb 2011)

30L is filled within 2 hours on 100G if you have right pressure. If you don't then your membrane will may not work in full effect. What does it mean? Well 50% filtration efficiency or much less leaving you with still polluted water at the end. Membranes work at full effect at recommended pressure only. So you may need a pressure pump for around 50 pounds.


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## GHNelson (12 Feb 2011)

Hi idris
Ive had a couple of RO units...it all depends if you have the space to install the larger RO units.
You will still get pure RO water with a smaller unit but it will take longer to produce.
30 litres would be way off the mark of producing RO water from a 50gpd unit.
15 litres would be more a reasonable amount produced if you have average mains pressure.
When its new that is...it will slow down with age/usage also.
3 units of RO water to 1 of tap water is a good starting mix.
Cheers
hoggie


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## idris (12 Feb 2011)

So am I right in thinking that whilst your tap preasure may (and I'm guessing here) result in 10l/min when nothing is attached to it, if it is attached to a RO unit the combined output of waste and filtered water might be only about 0.5l/min?


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## GHNelson (12 Feb 2011)

Hi
You will have larger amounts of waste water because you don't have the optimum working pressure to run the RO unit   flat out.
You will be fortunate to get 500ml RO water per minute.
This based on my memory on my own RO unit which has been removed as i had a new kitchen fitted just recently....so i cant test it.
When using the RO unit it produced about a 25ml/30ml every minute.So about 1500ml/1800ml every hour.
I used to fill a 5 litre bottle in about 2 and a half hours....approx.
So it all depends on what size unit you have... your own mains pressure....temperature...and how much waste has to be removed...to produce the RO water.
Regards
hoggie


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## idris (13 Feb 2011)

Is that 25-30ml total ouput or 25-30ml of filtered water? If it's the latter, how much waste was produced at the same time?
Without the filter did you only get 500ml per min? I've just checked mine and I can get 1l in about 4-5sec.


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## GHNelson (13 Feb 2011)

Hi 
That's filtered water.
As i said you will have alot of waste water because the mains pressure is to low to force the unfiltered water through the membrane at optimum working rate.
Why do you ask about the waste water?
I don't understand without the filter statement....do you mean when not in use?
hoggie


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## idris (13 Feb 2011)

I was asking about the output of your tap without the filter connected to get as sense of how high my mains water pressure is.
(I wasn't clear when you said "You will be fortunate to get 500ml per minute" whether you meant 500ml/min of filtered water only from the filter, or combined waste water plus filtered water, or whether you were suggesting 500ml/min was all you could expect out of a mains water tap without any filter attached.)





Sorry about the size!
So how quickly did you get 1litre out of your mains tap if you didn't have the RO filter fitted, and how much waste water did you get per minute if you were getting 25-30ml of filtered water per minute?

And what sort of flow rate from the tap would you need to get the RO unit to work at a sensible speed?
(I know flow rate and pressure aren't the same thing, but for this purpose I think it's a good enough comparison.)


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## GHNelson (13 Feb 2011)

Hi idris
I don't think you can make a comparison to much as i live in a 2 up flat.
I did a quick test 2 litres in 15 seconds so 8 litres in a minute.
If you switch your tap on fully and get a good amount of splashing I think you will have enough mains pressure to get some sort of filtered water.
I wasn't to concerned about waste water so i never monitored it.Here is a gauge that can be connected to the RO unit :arrow: http://www.osmotics.co.uk/water-pressur ... 0e813ec5a5 to give you a idea what your mains pressure is.
Also there maybe included with the RO unit a back flow push-fit connector this helps to increase the pressure and produce more RO water and less waste.
Hope this clears up a few points.
hoggie


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