RO/DI Not Removing All Copper From Water

Meloco14

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I moved into a new house and have been having issues with copper in the tap water. Levels are at 1.07ppm. Never thought about it affecting the tank because of my RO/DI unit. However something told me to test my tank water and indeed there is copper at .04. I tested my RO/DI water twice and both times it registered .1. Suffice it to say I am running cuprisorb in the tank and I'm throwing out my RO water and the fresh saltwater I was mixing. My question is, what part of the RO/DI is failing to remove all the copper? Is it the membrane, the carbon, or the DI resin? I will replace the carbon and DI regardless and rinse the membrane. The membrane is less than a year old. But which part of the filter is the culprit?
 

Dom

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I moved into a new house and have been having issues with copper in the tap water. Levels are at 1.07ppm. Never thought about it affecting the tank because of my RO/DI unit. However something told me to test my tank water and indeed there is copper at .04. I tested my RO/DI water twice and both times it registered .1. Suffice it to say I am running cuprisorb in the tank and I'm throwing out my RO water and the fresh saltwater I was mixing. My question is, what part of the RO/DI is failing to remove all the copper? Is it the membrane, the carbon, or the DI resin? I will replace the carbon and DI regardless and rinse the membrane. The membrane is less than a year old. But which part of the filter is the culprit?

Does a standard RODI system remove copper? You may need to add a stage. Following.
 

Randy Holmes-Farley

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A properly functioning RO/DI producing 0 ppm TDS water will not have problematic levels of copper (assuming you start with drinkable water). Both the Ro membrane and the DI remove it to a considerable extent. The carbon is not the main part that removes copper.

How did you measure that copper level?
 
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Meloco14

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A properly functioning RO/DI producing 0 ppm TDS water will not have problematic levels of copper (assuming you start with drinkable water). Both the Ro membrane and the DI remove it to a considerable extent. The carbon is not the main part that removes copper.

How did you measure that copper level?
I used a hanna checker. The product water always showed 0 tds but after testing with the hanna it showed .1 copper. I have fixed the issue by feeding the RO unit directly from the well with a garden hose, bypassing the copper pipes in the house. It's ugly with the hose running through the driveway but it works. But I am concerned my RO membrane may need to be replaced and it's less than a year old. I took it out to rinse it and the date of manufacture is 6/20. It's a spectrapure, good quality. Now I also need to resolve the issue of the copper leaching into my tap water.
 

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I used a hanna checker. The product water always showed 0 tds but after testing with the hanna it showed .1 copper. I have fixed the issue by feeding the RO unit directly from the well with a garden hose, bypassing the copper pipes in the house. It's ugly with the hose running through the driveway but it works. But I am concerned my RO membrane may need to be replaced and it's less than a year old. I took it out to rinse it and the date of manufacture is 6/20. It's a spectrapure, good quality. Now I also need to resolve the issue of the copper leaching into my tap water.
The Hanna copper testers are great for measuring copper at levels to quarantine or treat fish. They don’t, however, measures low levels of copper well. With a spectrapure membrane, I would be skeptical of the high copper results you are getting.
 
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Meloco14

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That's interesting, I didn't consider that. Maybe I should send in my RO for ICP, I've never done it before. It would be good to have a clear understanding of exactly what I'm using.
 

R33fDaddy

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If the Hanna Checker is showing .03 then that's basically Zero. The Hanna checker is super sensitive, if you get an icp test I bet it will reward zero copper.
 
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Meloco14

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Yes I did end up concluding the hanna checker was just getting false readings. It was showing small amounts of copper in my display but ICP shows zero. Crisis averted.
 

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I moved into a new house and have been having issues with copper in the tap water. Levels are at 1.07ppm. Never thought about it affecting the tank because of my RO/DI unit. However something told me to test my tank water and indeed there is copper at .04. I tested my RO/DI water twice and both times it registered .1. Suffice it to say I am running cuprisorb in the tank and I'm throwing out my RO water and the fresh saltwater I was mixing. My question is, what part of the RO/DI is failing to remove all the copper? Is it the membrane, the carbon, or the DI resin? I will replace the carbon and DI regardless and rinse the membrane. The membrane is less than a year old. But which part of the filter is the culprit?
4 stage RODI absolutely has to remove completely. If it isn't replace all filters and membrane. All filters go bad at the six month mark whether they have been used or not. ALL membranes need replaced at the 12 month mark.
 

Randy Holmes-Farley

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4 stage RODI absolutely has to remove completely. If it isn't replace all filters and membrane. All filters go bad at the six month mark whether they have been used or not. ALL membranes need replaced at the 12 month mark.

Seems excessive. There's no reason to replace a properly functioning RO membrane. I had my tank for 20 years, and only replaced the RO membrane once (when I got a whole new RO/DI system). :)
 

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Seems excessive. There's no reason to replace a properly functioning RO membrane. I had my tank for 20 years, and only replaced the RO membrane once (when I got a whole new RO/DI system). :)
All membranes say 1-2 years on the package. All filters say between 3-9 months. I from experience know for a fact that unless water is flowing through the membrane constantly, bacteria and other undesirables build up in both filters and membranes. Most ppl look at TDS. TDS has nothing to do with reefing whatsoever. I can use 112 TDS and I can use 8 TDS water side by side and neither tank would have a difference. Now what that TDS is comprised of means something.
 

Randy Holmes-Farley

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All membranes say 1-2 years on the package. All filters say between 3-9 months. I from experience know for a fact that unless water is flowing through the membrane constantly, bacteria and other undesirables build up in both filters and membranes. Most ppl look at TDS. TDS has nothing to do with reefing whatsoever. I can use 112 TDS and I can use 8 TDS water side by side and neither tank would have a difference. Now what that TDS is comprised of means something.

There's zero reason to replace a reef use RO membrane before the flow drops off or the rejection drops too much. It may never happen, and didn't in my case twice for 10 years each.

Certainly bacteria may grow between the RO membrane and the DI. That's no concern for reef use. Drinking by people? Sure, they need to be sanitized periodically for that reason.

Of course TDS is not the actual thing we care about. TDS is always used as a surrogate for RO/DI functionality. If the TDS is 0 ppm, the RO/DI is functioning and we can be assured that most things we care about (e.g., copper) are being removed in the expected fashion.

IMO, the only filter that might usefully be removed before there's an indication of an issue is the carbon block. All of the others can be replace only when needed based on pressure, flow, and TDS.

I discuss these issues here:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

These are my suggestions from it that are somewhat contrary to your suggestions:

Tips on Using RO/DI

If you have a pressure gauge on the RO membrane, change the sediment filter when the pressure drops to about 40 PSI. If the pressure does not rise adequately after replacing the sediment filter, change the carbon filter.

If you do not have a pressure gauge, change the sediment and carbon filters when the output of purified water becomes significantly reduced.

Avoid running the RO/DI if your town’s water system is flushing fire hydrants in your area, as the sediment and carbon filters will clog very fast.

If the sediment and carbon filters do not seem to get clogged, at least replace the carbon filter periodically to ensure that chlorine and chloramine are being broken down appropriately. Both of these can be measured with an inexpensive chlorine test kit if you want to be sure they are being removed.

If you have especially hard water, you might consider running it through a water softener before the RO/DI filter. That process removes calcium and magnesium by swapping sodium for them. While aquarists are not generally worried about calcium and magnesium in their source water, they can foul RO membranes by forming calcium and magnesium carbonate precipitates inside it. That precipitation will reduce flow and eventually make the membrane unusable.

Make sure that your waterline pressure is appropriately high (at least 40-60 PSI). In some situations where the pressure is low, an inline pump may be desirable before the RO/DI system to boost the pressure.

If there is excessive carbon dioxide in the source water (such as well water), you might consider degassing the water first to remove some of the carbon dioxide, and thereby reduce the rate of depletion of the DI resins. Note, however, that this option is not inexpensive, and typically involves repressurizing the water with a pump.

If you are evaluating an existing RO membrane and can collect water from the tap and after the RO membrane, the conductivity (in mS/cm or ppm TDS) should drop by a factor of more than 10 across it (to as much as 100), relative to the tap’s water. If the drop is less than a factor of 10, it is not working properly, and may have holes in it.

Monitor the DI resins by measuring the effluent’s conductivity, either with an inline meter (set to its most sensitive level), or by measuring the effluent manually. If you are using a TDS or conductivity meter, then the measured value should drop to near zero, or maybe 0-1 ppm TDS or 0-1 mS/cm. Higher values indicate that something is not functioning properly, or that the DI resin is becoming saturated and needs replacement. That does not necessarily mean, however, that 2 ppm TDS water is not OK to use. But beware that the flow of impurities and the conductivity may begin to rise fairly sharply when the resin becomes saturated. Do not agonize over 1 ppm versus zero ppm. While pure water has a TDS well below 1 ppm, uncertainties from carbon dioxide in the air (which gets into the water and ionizes to provide some conductivity; about 0.7 mS/cm for saturation with normal levels of CO2, possibly higher indoors) and the conductivity/TDS meter itself may yield results of 1 or 2 ppm even from totally pure water by not being exactly zeroed properly. Also note that the first impurities to leave the DI resin as it becomes saturated may be things that you are particularly concerned with (such as ammonia if your water supply uses chloramine or silica if there is a lot in the source water).

If you recharge your DI resins yourself, be very careful with the acid and base used, as they can be dangerous.
 
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