RO/DI membrane life expectancy
- Thread starter FreedR
- Start date
Buckeye Hydro
.Registered Member
Under normal conditions you should be getting years out of the membrane.
Sheac12 asks some good questions. Also, what is the tds of your feedwater?
With a new membrane, what is your waste to permeate ratio?
I wonder if when you think the membrane died is it actually very low pressure due to clogged prefilters?
Sheac12 asks some good questions. Also, what is the tds of your feedwater?
With a new membrane, what is your waste to permeate ratio?
I wonder if when you think the membrane died is it actually very low pressure due to clogged prefilters?
That is exactly what I was thinking, that the pre-filters have clogged and the actual pressure into the membrane has dropped too low. Combine that with a high tds at the input and you are in for some trouble!
lordofthereef
One reef to rule them all
My membrane is going on 2 years and is as good as the day I installed it. 4-5 months seems like way too short of a time period.
I think I used the wrong term. I mean the filters. How long do the filters last for you?
I have the 5-stage filter from here:
http://www.thefilterguys.biz/ro_di_systems.htm
I don't have a TDS meter. With new filters, there is a steady flow of DI water from the output, but it slows to a trickle. The filters now are visibly dirty, especially the first one.
And, how do you flush the system?
I have the 5-stage filter from here:
http://www.thefilterguys.biz/ro_di_systems.htm
I don't have a TDS meter. With new filters, there is a steady flow of DI water from the output, but it slows to a trickle. The filters now are visibly dirty, especially the first one.
And, how do you flush the system?
It would help to know the TDS before all fliters. Your water may be extreamly dirty and require a large pre-filter or more often filter changes.
Bulk Reef sells a in-line TDS meter for about 30 dollars I think it is. tells you input and output. A pressure gauge would help let you know if the 3 stage filter before the membrane is clogged as well.
Bulk Reef sells a in-line TDS meter for about 30 dollars I think it is. tells you input and output. A pressure gauge would help let you know if the 3 stage filter before the membrane is clogged as well.
Buckeye Hydro
.Registered Member
A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.
Also be cognizant of the chlorine capacity of the carbon block. The Matrikx+1 (“Chlorine Guzzler”) for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.
Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.
The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?
If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called “prefilters”) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.
The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.
After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm to 3 ppm, 5 ppm, and higher, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!
Also be cognizant of the chlorine capacity of the carbon block. The Matrikx+1 (“Chlorine Guzzler”) for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.
Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.
The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?
If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called “prefilters”) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.
The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.
After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm to 3 ppm, 5 ppm, and higher, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!
lordofthereef
One reef to rule them all
My system has two valves that when turned simultaneously will flush the membrane. I do this for 30 seconds twice a month.
lordofthereef
One reef to rule them all
Those filters don't get flushed. They last 6-12 months depending on the quality of the incoming water. If you water is especially bad, I can see this factor needing replacement every 6 months or so, which brings you closer to the timeline you originally spoke of.
Buckeye Hydro
.Registered Member
If you have heavy sediment loads, or other issues (like iron in the feedwater) your prefilters could clog very quickly - in a matter of days. This certainly isn't typical but we've seen it.
In the case of heavy sediment loads you can deal with this by adjusting the prefilters you use, and the order in which you use them.
What prefilters (the filters before the membrane) do you use? In what order? What do they look like after 4-5 months?
Russ
In the case of heavy sediment loads you can deal with this by adjusting the prefilters you use, and the order in which you use them.
What prefilters (the filters before the membrane) do you use? In what order? What do they look like after 4-5 months?
Russ
Buckeye Hydro
.Registered Member
Remember that the prefilters don't remove TDS, so the tds readings you see from the tap, RO water, or DI water really don't tell you anything directly about when it is time to change the sediment filter(s) and carbon filter(s). Use those tds readings to evaluate how the DI resin and RO membrane are doing their jobs.
Russ
SpectraPure
.Registered Member
We have posted many answers (and some the questions) here
http://www.reefcentral.com/forums/forumdisplay.php?f=229
Common troubleshooting, how to test your system etc etc.
bruce
http://www.reefcentral.com/forums/forumdisplay.php?f=229
Common troubleshooting, how to test your system etc etc.
bruce
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