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Buy second hand RO system ?

eminor

Member
Joined
5 Feb 2021
Messages
784
Location
France
Hello, was looking for an ro system, I came across a person who sells one and told me that it has been used very little, she lives in a region where the water is very soft. I read somewhere that in low to medium range of ro system, the filters cost as much as a new ro, does it worst bother with second hand ?

Does an ro water system that has not been used for a long time still work or do you have to change all the filters? thx
 
If for whatever reason I had to buy a second hand RO unit I would change the cartridge inside no matter what the original owners says specially when it involves your health or the one of your fish. There is always a gap between what people say and what you expect. And yes, the RO cartridge is the single most expensive item in an RO system. In my 5-stage filtering system, the RO membrane alone costs me around 70USD each time I change it (once every 1.5 year or less). All other cartridges like the carbon, sediments etc are quite cheap in comparison.

Does an ro water system that has not been used for a long time still work or do you have to change all the filters? thx
If water has been sitting inside the membrane cartridge without flow for a long time I think it could get damaged as pores could get clogged but don't quote me on that one.
 
If for whatever reason I had to buy a second hand RO unit I would change the cartridge inside no matter what the original owners says specially when it involves your health or the one of your fish. There is always a gap between what people say and what you expect. And yes, the RO cartridge is the single most expensive item in an RO system. In my 5-stage filtering system, the RO membrane alone costs me around 70USD each time I change it (once every 1.5 year or less). All other cartridges like the carbon, sediments etc are quite cheap in comparison.


If water has been sitting inside the membrane cartridge without flow for a long time I think it could get damaged as pores could get clogged but don't quote me on that one.
Thanks, i'll better buy it new, my water is hard GH 17 with lot of calcium, if i'm right filter gonna need a change more often ?

I need 100-150 liters per month
 
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Thanks, i'll better buy it new, my water is hard GH 17 with lot of calcium, if i'm right filter gonna need a change more often ?

I need 100-150 liters per month
My water is like liquid rock and I went through about 1000 litres a month and I used to change all my filters every 18 months regardless, Me personally I only buy new if my fish was dependent on that particular equipment.
 
My water is like liquid rock and I went through about 1000 litres a month and I used to change all my filters every 18 months regardless, Me personally I only buy new if my fish was dependent on that particular equipment.
What do you call liquid rock water ? i find soft water easier to manage and i only keep soft water plants and shrimp
 
What do you call liquid rock water ? i find soft water easier to manage and i only keep soft water plants and shrimp
very very hard, that's why I have a ro/di unit, not quite sure what you are saying, I merely pointed out that even hard water doesn't necessarily mean you need to change the filters more often, I went through alot more water than you and still only changed every 18 months, so dont be concerned about changing filters, they last longer than people think.
 
very very hard, that's why I have a ro/di unit, not quite sure what you are saying, I merely pointed out that even hard water doesn't necessarily mean you need to change the filters more often, I went through alot more water than you and still only changed every 18 months, so dont be concerned about changing filters, they last longer than people think.
i though i had to change it every 6 months, tds might be the best tool to check ?
 
i though i had to change it every 6 months, tds might be the best tool to check ?
The manufacturers tell you to change every 6 months just to get more money out of you, the amount of water you need is not a lot so your filters should last a long time.
I'm not sure the best way to check the filters as I changed every 18 months regardless, maybe someone more intelligent than me can help you with how best to check.
 
You do not mention what price that second hand system was, but yes it could be false economy, so do buy a new one.
A good small system to meet your needs is like one of these that has a DI resin unit to remove all traces.
You ideally need to change the Prefilter and Carbon block every 6 months, partly for the muck they collect and partly to reduce bacteria build up,
Using a TDS pen on the product water will show if its pure, as the DI Resin and RO membrane become ineffective the value will rise and indicate when they need renewal.
How long that takes is hard to say, but on your needs think it will be years.

Ultra-Pure 4 Stage 50 Gallon Per Day RODI System
 
Currently I am making about 250 L per month with my RODI system (Aquactic Life RO buddie 100 GPD). I used to be much more picky on when to change the cartridges. Right now the Deionization (DI) cartridge probably needs to be replaced (and will do so in a month or two), but I am still getting water with a TDS of 4-5 ppm. When all the cartridges are brand new I get about 1-2 ppm. A 3 piece bundle usually sets me back around $40... Carbon, Sediment and Deionization - the membrane is $30. Aquactic Life claims a lifetime of 6 month or 6000 L (for the Sediment and Carbon filters) but it will vary depending on your tap water... I can keep mine going for 12 months. When you start to see a spike in TDS and/or the production rate going down significantly you know it's time to change... changing before any of this happens is just a waste of money. One caveat worth keeping in mind though, which is often overlooked, is if your tap is highly chlorinated you may have to change the carbon filter more often as you will have a hard time detecting that from a spike in TDS alone. Furthermore, many 4-stage RODI system will not be able to effectively remove chloramine if at elevated levels.

Cheers,
Michael
 
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Thanks guys so much good informations, i decided to buy a new one, at least i'll be certain that everything will be working. There is a pros with ro system, i can make custom tea and coffee :cool:
 
Your RO membrane lifetime is directly correlated to the tap water TDS. The higher it is the least amout of time it will last. I had one RO membrane suddenly go bad on me pretty fast because the TDS of the tap water jumped from ~200/300 TDS to >~1200 TDS for several weeks. The membrane was less than a year old but that TDS increase exhausted the membrane much faster.
 
Ouch! Any idea what made the tap jump to that level? specifically what element/compound.

Cheers,
Michael
Winter > drought > Bkk is close to the sea > sea water sipping inland > BOOM > Na all over the place + the water company adding way more chlorine to compensate the lower water quality during the season. Filtering system got overwhelmed.

With the tap water, you could actually taste the salt when brushing your teeth or taking a shower.
 
Winter > drought > Bkk is close to the sea > sea water sipping inland > BOOM > Na all over the place + the water company adding way more chlorine to compensate the lower water quality during the season. Filtering system got overwhelmed.

With the tap water, you could actually taste the salt when brushing your teeth or taking a shower.
Hi @Hanuman, Wow! I see - makes sense. Yeah, salt water contamination would spike the water tremendously - the TDS of sea water is routinely 35000-40000 ppm.. 1200 ppm would clog up an RO system in no time!

Cheers,
Michael
 
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Your RO membrane lifetime is directly correlated to the tap water TDS. The higher it is the least amout of time it will last. I had one RO membrane suddenly go bad on me pretty fast because the TDS of the tap water jumped from ~200/300 TDS to >~1200 TDS for several weeks. The membrane was less than a year old but that TDS increase exhausted the membrane much faster.
I'm from Calais, close to UK, i have lots of luck, my calibrated tds always tell me between 240-260ppm anytime in the year. 1200 is insane
 
A last question guys, i've read on manual that it's needed to flush the ro to increase membrane lifespan. I have no flush valve, so i have to do it manually. If i understand well, i need to disconnect the flow restrictor on the waste line, and let the water go ? but for how long ? thx
 
Thanks for the suggestion. I want to buy an RO system and I want to know if is it worth buying a second RO system. :)
 
Currently I am making about 250 L per month with my RODI system (Aquactic Life RO buddie 100 GPD). I used to be much more picky on when to change the cartridges. Right now the Deionization (DI) cartridge probably needs to be replaced (and will do so in a month or two), but I am still getting water with a TDS of 4-5 ppm. When all the cartridges are brand new I get about 1-2 ppm. A 3 piece bundle usually sets me back around $40... Carbon, Sediment and Deionization - the membrane is $30. Aquactic Life claims a lifetime of 6 month or 6000 L (for the Sediment and Carbon filters) but it will vary depending on your tap water... I can keep mine going for 12 months. When you start to see a spike in TDS and/or the production rate going down significantly you know it's time to change... changing before any of this happens is just a waste of money. One caveat worth keeping in mind though, which is often overlooked, is if your tap is highly chlorinated you may have to change the carbon filter more often as you will have a hard time detecting that from a spike in TDS alone. Furthermore, many 4-stage RODI system will not be able to effectively remove chloramine if at elevated levels.

Cheers,
Michael


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