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No matter what your water quality at the tap is you should be getting 0-1 after the DI unit. I assume your membrane is good. If so:
Find the pressure level at your tap feed and compare it to your RO/DI mfg requirements. If it's high enough take the RO/DI back or just get a new one. If your pressure is low you need the booster pump to get it to within pressure range. Any RO membrane must have a certain pressure level to operate correctly. If you have pressure problems and need multi DI units then I feel you are feeding the DI units too much "crap" and you will go thru more of them than you can ever justify.
My strong recommendation is: get a pressure reading at your tap and go from there.
Find the pressure level at your tap feed and compare it to your RO/DI mfg requirements. If it's high enough take the RO/DI back or just get a new one. If your pressure is low you need the booster pump to get it to within pressure range. Any RO membrane must have a certain pressure level to operate correctly. If you have pressure problems and need multi DI units then I feel you are feeding the DI units too much "crap" and you will go thru more of them than you can ever justify.
My strong recommendation is: get a pressure reading at your tap and go from there.
You NewYorker should be grateful for the nice Hudson water. I have hard artesian well and hard Colorado water as water supply and the following is my readings:
Tap: 454.5 ppm
RO: 13.45 ppm
DI: 0.11 ppm (0.16 uS or ~5.9MOhm)
You need to make sure the TDS meter is calibrated, and take the measurements for DI when the water is running. This is because slight contaniment can ruin the reading. For example, the first few fl. oz. of DI water is ~6-8 ppm, but after running the DI for a few minutes (cleaning the TDS probe and get the stailed water out) drop the reading down to 0.11 ppm. CO2 is also a big factor that can ruin the reading, but it usually does not get a good water (less than 1 ppm) up to 8ppm as in your case.
Tap: 454.5 ppm
RO: 13.45 ppm
DI: 0.11 ppm (0.16 uS or ~5.9MOhm)
You need to make sure the TDS meter is calibrated, and take the measurements for DI when the water is running. This is because slight contaniment can ruin the reading. For example, the first few fl. oz. of DI water is ~6-8 ppm, but after running the DI for a few minutes (cleaning the TDS probe and get the stailed water out) drop the reading down to 0.11 ppm. CO2 is also a big factor that can ruin the reading, but it usually does not get a good water (less than 1 ppm) up to 8ppm as in your case.
The same is true if you test the product output from the RO unit right after it begins processing because the membrane will allow a certain amount of junk to pass through. Let it run for a minute or two before testing the output.
I just replaced my 75 gpd membrane last night, and all of my cartridges last week. Here are my readings:
tap - 153 TDS
post RO - 10 TDS
post 1st DI - 2 TDS
post 2nd DI - 0 TDS
Before I replaced the RO membrane, the output from my 3.5 month old membrane had creapt up to 40 TDS. I am still trying to figure out why my RO membranes deteriorate so quickly (you can see my recent thread on this topic for details).
I just replaced my 75 gpd membrane last night, and all of my cartridges last week. Here are my readings:
tap - 153 TDS
post RO - 10 TDS
post 1st DI - 2 TDS
post 2nd DI - 0 TDS
Before I replaced the RO membrane, the output from my 3.5 month old membrane had creapt up to 40 TDS. I am still trying to figure out why my RO membranes deteriorate so quickly (you can see my recent thread on this topic for details).
I guess the Michigan water is pretty good too. Last time I live in Chicago, the water tasted a bit funny because of the algae bloom in the Lake. 153 ppm TDS is 1/3 of what we have here in So. Cal.
Milz, you may want to check your prefilters. For example, if the carbon is not doing its job, the chlorine can kill the membrane in a couple of months with moderate amont of topoffing (several gal. per day). Another thing to look for is water pressure. But I doubt that is an issue with the water facility in Chicago.
Milz, you may want to check your prefilters. For example, if the carbon is not doing its job, the chlorine can kill the membrane in a couple of months with moderate amont of topoffing (several gal. per day). Another thing to look for is water pressure. But I doubt that is an issue with the water facility in Chicago.
David Magen":2otneopx said:I guess the Michigan water is pretty good too. Last time I live in Chicago, the water tasted a bit funny because of the algae bloom in the Lake. 153 ppm TDS is 1/3 of what we have here in So. Cal.
Milz, you may want to check your prefilters. For example, if the carbon is not doing its job, the chlorine can kill the membrane in a couple of months with moderate amont of topoffing (several gal. per day). Another thing to look for is water pressure. But I doubt that is an issue with the water facility in Chicago.
Good points.
WRT the prefilters, I replace them at the same time I switch over the DI cartridges, which is probably every 3-4 months. Nevertheless, I have looked into the chlorine issue. I have been told by the guys at Aquatic Reef Systems that the standard carbon pre-filters should be sufficient unless the municiple water department uses chlorimins (sp?). They claim that they do not. But I am looking into having the water tested just to make sure. If it turns out that chlorine IS the problem, I understand that high capacity carbon units are available.
WRT to water pressure, indeed this may be a problem. I live in a newly built high-rise which has not yet reached full occupancy. As a result, the water pressure tends to fluctuate throughout the day. A booster pump would help, but won't eliminate fluctuations. I am hoping to ride this out until the building is full, at which time the building engineer has told me that the water system will be balanced.
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