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How much water does Reverse Osmosis filter system waste ?

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  • Mar 1st, 2019 7:19 pm
[OP]
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Jun 7, 2005
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How much water does Reverse Osmosis filter system waste ?

I just learned that RO filter system can waste lot of water. I didn’t know or pay attention to it in the past. I remember when I was finishing my basement, the contractor told me that there was water going to the drain constantly and I didn’t know where it came from and forgot about it. Now, I am thinking it could be coming from the RO system.

I wonder how we can check how much water the RO system is wasting. Is new RO system better (My system is over 15 years old) ? If so, maybe I should replace the existing one with one from Costco.

Thanks for any advice.
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Sep 22, 2009
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3:1 or 4:1
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Dec 6, 2006
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It's mostly the RO membrane. You did replace that and the pre filters regularly I assume?

There is a line going to clean RO water tank and a waste line. So if u want, can easily time and measure what the waste ratio is. It depends on the type of membrane, input water pressure, and your setup ( can be adjustable). For the same membrane n pressure, if u tune the setup to do less watse water, the faster the membrane starts to clog, which you need to flush regularly and eventually replace.
[OP]
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Jun 7, 2005
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My system comes with two big tubes, one for carbon filter and the other is for particular filter, and I remember there was another smaller size filter on top of them laying horizontally (forgot what it is). And I usually only change them annually, and I have changed that small filter two years ago. Believe or not, I am still using the original membrane as I was told that if the membrane breaks, I will notice from the digital tester reading right away. It is still usually around 5-10 (I forgot the unit of measure) from the reading. I believe the water comes from RO system is usually within 30.

Does it mean all RO systems are similar and the amount of waste depends on how we tune the membrane ?
boyohboy wrote: It's mostly the RO membrane. You did replace that and the pre filters regularly I assume?

There is a line going to clean RO water tank and a waste line. So if u want, can easily time and measure what the waste ratio is. It depends on the type of membrane, input water pressure, and your setup ( can be adjustable). For the same membrane n pressure, if u tune the setup to do less watse water, the faster the membrane starts to clog, which you need to flush regularly and eventually replace.
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Dec 6, 2006
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rdx wrote: My system comes with two big tubes, one for carbon filter and the other is for particular filter, and I remember there was another smaller size filter on top of them laying horizontally (forgot what it is). And I usually only change them annually, and I have changed that small filter two years ago. Believe or not, I am still using the original membrane as I was told that if the membrane breaks, I will notice from the digital tester reading right away. It is still usually around 5-10 (I forgot the unit of measure) from the reading. I believe the water comes from RO system is usually within 30.

Does it mean all RO systems are similar and the amount of waste depends on how we tune the membrane ?
The tuning part is basically adjusting the outlet pressure after the membrane. Higher outlet pressure - forces more water through membrane - more fraction of clean water and less waste. Not every to sys has adjustable valves to let u tune.

The membrane probably won't break, but as it ages It's more clogged so becomes more difficult for water to filter through and in turn more waste water.
[OP]
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Jun 7, 2005
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boyohboy wrote: The tuning part is basically adjusting the outlet pressure after the membrane. Higher outlet pressure - forces more water through membrane - more fraction of clean water and less waste. Not every to sys has adjustable valves to let u tune.

The membrane probably won't break, but as it ages It's more clogged so becomes more difficult for water to filter through and in turn more waste water.
I see. I am not sure if my old system have the pressure valve, probably no...........

Regarding the membrane, I didn't know it won't break. As I mentioned, the store who sold me said when it breaks, it will not filter.......... And they said changing it regularly (even it doesn't break) is for hygiene purpose).

Anyway, based on what you said, the original membrane on my 15 years old system is probably pretty clogged. So, I wonder if I should completely change the new system as the old system 15 years old. I see Costco is selling a 5 stages system for only $189. By the way, is 5 stage better than my existing 3 stages (I can see more # of filters I need to change every year LOL) ? Also, since I already have all piping from the existing system, can I assume it is easy for me to DIY and switch a new system ? Thanks

https://www.costco.ca/Vitapur-5-stage-Q ... 59986.html

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[OP]
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Jun 7, 2005
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By the way, my system looks like this one but not Watts brand though. I guess it is a 4 stages. I notice there are systems from 2 stages to 7 stages. Is more stages always better? Like I said, I usually only change the carbon and sediment filters annually. How often do we need to change the other two (inline and membrane) ?

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Last edited by rdx on Feb 26th, 2019 2:12 pm, edited 1 time in total.
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Feb 11, 2007
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I think they can be as bad as 1:20, but I think some claim zero waste, which I don't see how that's possible. Maybe 1:1 with a high pressure pump?
Where do you live that you need such a system? Keep in mind that your water will also have few good minerals, so then you need a re-mineralizer for taste and health.
We just use a carbon filter to remove chlorine from the city water.
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[OP]
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Jun 7, 2005
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I found this universal RO system membrane from Amazon for only $20-30 (depend on GPD). Do you think it will fit my system ? If so, I guess I will try that instead of replacing the whole system. By the way, should I get the one with the highest GDP (100) ? Does it represent how fast the water can pass ? Thanks

https://www.amazon.ca/SAVEMORE4U18-Univ ... hi&sr=1-27
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rdx wrote: I found this universal RO system membrane from Amazon for only $20-30 (depend on GPD). Do you think it will fit my system ? If so, I guess I will try that instead of replacing the whole system. By the way, should I get the one with the highest GDP (100) ? Does it represent how fast the water can pass ? Thanks

https://www.amazon.ca/SAVEMORE4U18-Univ ... hi&sr=1-27
Yeah higher GPD is generally better, but needs your setup to be setup for that. Your system will def has a pressure valve, that's what make the RO works, just that it is either fixed (for a certain GPD rating) or adjustable.

For a 15 y/o system... just get a whole new set, if nothing else just for hygiene reason.
The RO membrane is supposedly to be flushed regularly, depending on usage... if your system has a flush "valve" which's basically a by-pass to the pressure valve so you just run the water all output to waste without filtering.

For the num of stages... have to see the spec. Usually the last stage mounted horizontal after the membrane is just for "taste". It adds back some minerals to the RO so it tastes more normal... or whatever. You may also find some RO/DI setup which has a DeIonization resin filter after the membrane. For drinking/cooking you really don't need that. RO/DI can bring TDS down to 0 ppm, but resin needs to be replaced.

The stages before membrane... the usual sediment filters & carbon block. For 4+ stages, first 2 are usually sediment filters, 1 coarser grain (cheaper, 10+ micron) and 1 finer grain (slightly more expensive, <5 micron).
[OP]
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Jun 7, 2005
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Thanks for all information. I guess 4 stages (carbon, sediment, inline and membrane) is good enough, right ? If I am changing a new system, I am thinking to get the Watts system as I found it is easier and cheaper to buy its filter replacement either from Home Depot/Amazon. What do you think ? Thanks again.

By the way, I forgot to mention that when the water filter guy came two years ago, he did a process to put solution and clean the water tank for me. So, if the tank is clean, all filters are changed, would it be ok ? Or I should still to change a new system ?

https://www.amazon.ca/dp/B000E77I0E?aax ... B000E77I0E
boyohboy wrote: Yeah higher GPD is generally better, but needs your setup to be setup for that. Your system will def has a pressure valve, that's what make the RO works, just that it is either fixed (for a certain GPD rating) or adjustable.

For a 15 y/o system... just get a whole new set, if nothing else just for hygiene reason.
The RO membrane is supposedly to be flushed regularly, depending on usage... if your system has a flush "valve" which's basically a by-pass to the pressure valve so you just run the water all output to waste without filtering.

For the num of stages... have to see the spec. Usually the last stage mounted horizontal after the membrane is just for "taste". It adds back some minerals to the RO so it tastes more normal... or whatever. You may also find some RO/DI setup which has a DeIonization resin filter after the membrane. For drinking/cooking you really don't need that. RO/DI can bring TDS down to 0 ppm, but resin needs to be replaced.

The stages before membrane... the usual sediment filters & carbon block. For 4+ stages, first 2 are usually sediment filters, 1 coarser grain (cheaper, 10+ micron) and 1 finer grain (slightly more expensive, <5 micron).
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Jan 28, 2007
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Skip the RO with a tank, as we had one and it wastes a lot of water regardless. Did some research and bought a 3 stage filter system that works IMO just as well, without the water waste.
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Dec 6, 2006
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rdx wrote: Thanks for all information. I guess 4 stages (carbon, sediment, inline and membrane) is good enough, right ? If I am changing a new system, I am thinking to get the Watts system as I found it is easier and cheaper to buy its filter replacement either from Home Depot/Amazon. What do you think ? Thanks again.

By the way, I forgot to mention that when the water filter guy came two years ago, he did a process to put solution and clean the water tank for me. So, if the tank is clean, all filters are changed, would it be ok ? Or I should still to change a new system ?

https://www.amazon.ca/dp/B000E77I0E?aax ... B000E77I0E
I'd change whole setup. It's not much more anyway, esp after 15 years! Who knows how clean or dirty it is even after being "cleaned"...
Make sure get a system using standard 10" size filters, so you can find (much!) cheaper replacement in HD/Lowes/Amazon/Ebay. Don't fall for those fancy skinny yet expensive system using proprietary size filters.
Jojo_Madman wrote: Skip the RO with a tank, as we had one and it wastes a lot of water regardless. Did some research and bought a 3 stage filter system that works IMO just as well, without the water waste.
Not sure what you mean by "skip RO with a tank". You mean skip RO altogether, or just skip the tank?
The tank is just for convenient as RO water production is slow. You don't want to wait 5 min to fill up a cup, when you don't have the storage tank. The tank doesn't affect among of waste water of the RO system in any way.
And "3 stage.... without water waste"... if there's no waste, then it's either not RO (only straight through sediment and carbon filters), or (unlikely) it has some sort of "disposable" RO membrane which just forces all water through but it'll clogged very quickly. Remember the purpose of the waste water is actually to continually wash away the impurities. Without waste outflow, a RO membrane won't last long.
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boyohboy wrote: I'd change whole setup. It's not much more anyway, esp after 15 years! Who knows how clean or dirty it is even after being "cleaned"...
Make sure get a system using standard 10" size filters, so you can find (much!) cheaper replacement in HD/Lowes/Amazon/Ebay. Don't fall for those fancy skinny yet expensive system using proprietary size filters.



Not sure what you mean by "skip RO with a tank". You mean skip RO altogether, or just skip the tank?
The tank is just for convenient as RO water production is slow. You don't want to wait 5 min to fill up a cup, when you don't have the storage tank. The tank doesn't affect among of waste water of the RO system in any way.
And "3 stage.... without water waste"... if there's no waste, then it's either not RO (only straight through sediment and carbon filters), or (unlikely) it has some sort of "disposable" RO membrane which just forces all water through but it'll clogged very quickly. Remember the purpose of the waste water is actually to continually wash away the impurities. Without waste outflow, a RO membrane won't last long.
Yes, yes, poor choice of wording ... RO systems are outdated now with the newer 3 stage disposable cartridge filtering systems ... personally, I'd never go back to an RO again, and we had a top of the line system too which I regret ever buying

Absolutely no problem filling cups in seconds or water jugs with our 3 stage filter system, but mind you we also have excellent water pressure here.
Filters last a long time without clogging, so I don't know what your talking about ... best part is any impurities go out with the filters.

Someone has been drinking the RO koolaid by the sounds of it ...
I'd rather be outdoors camping, kayaking, and mountain biking ...
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Jojo_Madman wrote: Yes, yes, poor choice of wording ... RO systems are outdated now with the newer 3 stage disposable cartridge filtering systems ... personally, I'd never go back to an RO again, and we had a top of the line system too which I regret ever buying

Absolutely no problem filling cups in seconds or water jugs with our 3 stage filter system, but mind you we also have excellent water pressure here.
Filters last a long time without clogging, so I don't know what your talking about ... best part is any impurities go out with the filters.

Someone has been drinking the RO koolaid by the sounds of it ...
Care to share what magic 3 stages sys u have?
As I said, without waste water, it's either not to or use disposable membrane..
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boyohboy wrote: Care to share what magic 3 stages sys u have?
As I said, without waste water, it's either not to or use disposable membrane..
Who said anything about being magical ... not sure why you got your panties in a knot?

They call it a four stage even though it has 3 cartridges in looking it up ... not sure why.
The best part is that it isn't anything more than a RainFresh System 3 ... only difference is we run 2 of the upgraded carbon filters (chloramine, Lead, VOC, etc) in place of a sediment and carbon.
I'd rather be outdoors camping, kayaking, and mountain biking ...
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Check out the Watts ZeroWaste pump that takes the R/O waste water (which would normally go down the drain) and pumps it back into your water system.
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Cough wrote: Check out the Watts ZeroWaste pump that takes the R/O waste water (which would normally go down the drain) and pumps it back into your water system.
It's not true 0 waste. It pumps this brine in of the hot water line. So it's not "waste"

Like I said the best option is actually a permeate pump. It'll drastically reduce the brine produced.
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Jojo_Madman wrote: Who said anything about being magical ... not sure why you got your panties in a knot?

They call it a four stage even though it has 3 cartridges in looking it up ... not sure why.
The best part is that it isn't anything more than a RainFresh System 3 ... only difference is we run 2 of the upgraded carbon filters (chloramine, Lead, VOC, etc) in place of a sediment and carbon.
Sorry but don't think you know what RO is. You kept saying 3 stages or 4. Num of stages doesn't matter. RainFresh System 3 is not RO, it's just straight through sediment/carbo (or whatever you want to put in the housings, again doesn't matter), and there's no RO membrane.
Not saying anyone needs RO or not, which is a separate discussion. As I said, no waste water = either not RO or have (wasteful) disposable membrane.
Cough wrote: Check out the Watts ZeroWaste pump that takes the R/O waste water (which would normally go down the drain) and pumps it back into your water system.
All the different "No waste" "Zero Waste" RO are just marketing names. There is always waste water output. Only difference being if you connect the waste water out to the drain, to another tank/storage, or back to water pipes.
Frankly tho, the waste water out from RO unit is not dirty at all, just that it has higher TDS (mostly carbonate) than your tap water (how much higher depends on your waste/good water ratio). It's been through the sediment/carbon filters as well so in fact it's somewhat cleaner than tap.

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