A
Anonymous
Guest
I mentioned in another post about my efforts to erradicate a hair algae problem that the problem was most likely the result of a failure of my RO membrane that went undetected for several months. After further investigation, I have some additional thoughts as to what happened and how the problem might be avoided. I hope this is of help to anyone setting up a similar RO/DI system.
My RO/DI system configuration:
I have a Kent Maxxima RO/DI unit that has been upgraded with a 75 gpd membrane and connected to a 10 gal bladder tank and a drinking water kit. Water is fed to my RO membrane after passing through micron and carbon pre-filters. The output from the RO membrane is split into three separate lines, the first being connected to a drinking water faucet, the second to the bladder tank, and the third to a pair of DI cartridges. As I will explain below, the third line is what I use to top-off my tank.
In this configuration, the RO unit will produce water whenever water is drawn off through either the drinking water faucet or the tank top-off line outlets. More specifically, when ever water is drawn off through either of these outlets, the water is initailly supplied by the processed water in the bladder tank. As the amount (and pressure) of water in the bladder tank decreases, the RO unit begins to process water and continues until the outlets have been closed AND the bladder tank has been re-filled.
As far as I know, the above description is a typical configuration for a RO system with a bladder tank and drinking water kit.
My top-off arrangement:
My RO/DI system is located on the opposite side of the room from my reef tank. I therefore do not have the RO/DI system permanently connected to my tank. When ever I need to top-off my tank, I connect a 1/4" line between my sump and the top-off outlet of the RO/DI system, and open a valve to allow water to flow from the bladder tank/RO membrane, through my DI cartridges, and to my sump. A Kent float valve in my sump prevents me from over-filling my tank.
I usually hook up my tank before I go to bed, and let my tank top-off over night.
The problems with my arrangement:
I have recently learned that RO membranes allow a small quantity of relatively un-pure water to pass through the membrane each time the membrane begins to process water. Obviously, the more times that the RO system starts up, the greater the quantity of impurities (ie, total dissolved solids) that will to pass through the system. I have seen this when testing my RO output immediately after initial water processing by the membrane. I have also been told that increasing the number of time the RO membrane kicks in shortens the life of the membrane.
Now in my system, most of the impurities will be captured by the DI units. The DI units will, however, become exhausted much more quickly. This is only aggravated by the manner in which I top off my tank.
My tank and sump hold around 400 gallons, net. Depending on the season, I evaporate 3-6 gallons per day. When I hook my sump up to the RO/DI system at night, the water that has evaporated durig the day is quickly replaced by the water stored in my bladder tank. Not too quickly, however, since I use a flow restricter valve to reduce the rate of flow (to increase contact time) through the DI cartridges. In any event, the sump is usually topped-off within an hour or two.
Now for the problem. Because I leave my sump connected to the RO/DI system throughout the night, the RO/DI system acts like an automatic top-off system and replaces water as it evaporates during the night. This is fine until the bladder tank has been re-filled (probably within 2-3 hours). After that, the RO membrane will repeatedly kick in to produce small quantities of water as it evaporates from my tank. As I explained above, this water will likely have very high TDS and will quickly exhaust my DI cartridges.
My hair algae outbreak appears to be a direct result of this problem. Hair algae first became a problem earlier this year, and seemed to coincide with a three week trip I had taken in South America. At that time, I had someone come-in and check on the tank and feed my fish every 2-3 days. But to avoid having my fish-sitter deal with topping-off the tank, I left my RO/DI system connected to the tank 24/7. When I returned from my trip, the tank had some serious algae problems. At the time, I figured it was the result of over-feeding. But now, I believe that because the RO membrane would repeatedly kick-in to produce small amounts of top-off water as the water evaporated from my tank, the level and quantity of TDS that was being allowed to pass through the system quickly overwelmed by DI cartridges and corrupted by RO membrane. As I mentioned above, it took me sometime to figure out that there was a problem with my RO/DI system, and even longer to figure out what the problem is.
Possible solutions:
As an inital step, I plan to add a vavle to the output from my RO membrane so that I can isolate the RO membrane from the water stored in the baldder tank and the two outlets (the drinking water faucet and the top-off output for my tank). I will close this valve before connecting my sump to the RO/DI system. Thus, only the water in my bladder tank will be used to top-off my tank, and I can leave the tank connected throughout the night. In the morning, after disconnecting the tank from my RO/DI system, and I will then open the valve to allow RO membrane to process water continuously until the bladder tank has been re-filled. The result will be that the RO membrane will start-up production of water only once per day, as opposed to who know how many times per day it had been forced to start-up.
The only other time the RO membrane might kick in is if, after the bladder tank has been re-filled, water is drawn off the system through the drinking water faucet. But this should not be significant since I don't use that water for much other than making coffee.
One problem that I still need to resolve is what I should do when out of town. My 10 gallon bladder tank is not large enough to store more than 1-2 days worth of water. One possible solution is a water level sensor that will open a valve connected to my top-off water supply line when the water drops in my sump 2-3 gallons, and shuts off after 2-3 gallons have been added to the sump. I am aware of these types of sensors connected to top-off pumps, but not to valves that can regulate flow from a pressurized bladder tank.
I would gladly welcome any and all comments, thoughts or suggestions on any of the above.
My RO/DI system configuration:
I have a Kent Maxxima RO/DI unit that has been upgraded with a 75 gpd membrane and connected to a 10 gal bladder tank and a drinking water kit. Water is fed to my RO membrane after passing through micron and carbon pre-filters. The output from the RO membrane is split into three separate lines, the first being connected to a drinking water faucet, the second to the bladder tank, and the third to a pair of DI cartridges. As I will explain below, the third line is what I use to top-off my tank.
In this configuration, the RO unit will produce water whenever water is drawn off through either the drinking water faucet or the tank top-off line outlets. More specifically, when ever water is drawn off through either of these outlets, the water is initailly supplied by the processed water in the bladder tank. As the amount (and pressure) of water in the bladder tank decreases, the RO unit begins to process water and continues until the outlets have been closed AND the bladder tank has been re-filled.
As far as I know, the above description is a typical configuration for a RO system with a bladder tank and drinking water kit.
My top-off arrangement:
My RO/DI system is located on the opposite side of the room from my reef tank. I therefore do not have the RO/DI system permanently connected to my tank. When ever I need to top-off my tank, I connect a 1/4" line between my sump and the top-off outlet of the RO/DI system, and open a valve to allow water to flow from the bladder tank/RO membrane, through my DI cartridges, and to my sump. A Kent float valve in my sump prevents me from over-filling my tank.
I usually hook up my tank before I go to bed, and let my tank top-off over night.
The problems with my arrangement:
I have recently learned that RO membranes allow a small quantity of relatively un-pure water to pass through the membrane each time the membrane begins to process water. Obviously, the more times that the RO system starts up, the greater the quantity of impurities (ie, total dissolved solids) that will to pass through the system. I have seen this when testing my RO output immediately after initial water processing by the membrane. I have also been told that increasing the number of time the RO membrane kicks in shortens the life of the membrane.
Now in my system, most of the impurities will be captured by the DI units. The DI units will, however, become exhausted much more quickly. This is only aggravated by the manner in which I top off my tank.
My tank and sump hold around 400 gallons, net. Depending on the season, I evaporate 3-6 gallons per day. When I hook my sump up to the RO/DI system at night, the water that has evaporated durig the day is quickly replaced by the water stored in my bladder tank. Not too quickly, however, since I use a flow restricter valve to reduce the rate of flow (to increase contact time) through the DI cartridges. In any event, the sump is usually topped-off within an hour or two.
Now for the problem. Because I leave my sump connected to the RO/DI system throughout the night, the RO/DI system acts like an automatic top-off system and replaces water as it evaporates during the night. This is fine until the bladder tank has been re-filled (probably within 2-3 hours). After that, the RO membrane will repeatedly kick in to produce small quantities of water as it evaporates from my tank. As I explained above, this water will likely have very high TDS and will quickly exhaust my DI cartridges.
My hair algae outbreak appears to be a direct result of this problem. Hair algae first became a problem earlier this year, and seemed to coincide with a three week trip I had taken in South America. At that time, I had someone come-in and check on the tank and feed my fish every 2-3 days. But to avoid having my fish-sitter deal with topping-off the tank, I left my RO/DI system connected to the tank 24/7. When I returned from my trip, the tank had some serious algae problems. At the time, I figured it was the result of over-feeding. But now, I believe that because the RO membrane would repeatedly kick-in to produce small amounts of top-off water as the water evaporated from my tank, the level and quantity of TDS that was being allowed to pass through the system quickly overwelmed by DI cartridges and corrupted by RO membrane. As I mentioned above, it took me sometime to figure out that there was a problem with my RO/DI system, and even longer to figure out what the problem is.
Possible solutions:
As an inital step, I plan to add a vavle to the output from my RO membrane so that I can isolate the RO membrane from the water stored in the baldder tank and the two outlets (the drinking water faucet and the top-off output for my tank). I will close this valve before connecting my sump to the RO/DI system. Thus, only the water in my bladder tank will be used to top-off my tank, and I can leave the tank connected throughout the night. In the morning, after disconnecting the tank from my RO/DI system, and I will then open the valve to allow RO membrane to process water continuously until the bladder tank has been re-filled. The result will be that the RO membrane will start-up production of water only once per day, as opposed to who know how many times per day it had been forced to start-up.
The only other time the RO membrane might kick in is if, after the bladder tank has been re-filled, water is drawn off the system through the drinking water faucet. But this should not be significant since I don't use that water for much other than making coffee.
One problem that I still need to resolve is what I should do when out of town. My 10 gallon bladder tank is not large enough to store more than 1-2 days worth of water. One possible solution is a water level sensor that will open a valve connected to my top-off water supply line when the water drops in my sump 2-3 gallons, and shuts off after 2-3 gallons have been added to the sump. I am aware of these types of sensors connected to top-off pumps, but not to valves that can regulate flow from a pressurized bladder tank.
I would gladly welcome any and all comments, thoughts or suggestions on any of the above.
And I agree with you that all the cartridges should be switched out together and on a regular basis. But 9 months way be way to long for many depending on how much water they process.
