GHill762 Posted December 11, 2012 Share Posted December 11, 2012 I'm replacing the filter cartridges in my RO/DI unit for the first time, it has 3 spots for filters before the membrane. Would I be better off doing: a) 1 micron sediment : .5 micron sediment : .6 micron carbon .5 micron sediment : 1 micron carbon : .6 micron carbon currently it's a sediment filter then 2 carbon filters, I don't know how course each is. I ordered filters thinking that there were only 2 stages before the membrane, so I have a .5 micron sediment and a .6 micron carbon to work with, I would have to pick the other up locally (or move the second carbon block forward to be the first carbon block, putting the new carbon filter at the 3rd stage). Also, keep in mind that we are on a well with pretty good water quality, but it is very high in dissolved minerals, and I don't need to worry about chlorine getting to the membrane. any thoughts? advice? Thanks, Garrett Link to comment
AZDesertRat Posted December 11, 2012 Share Posted December 11, 2012 Stick with what you ordered for best performance and replumb the extra canister into a DI so if you now have a single DI you have dual DI or if you have little horizontal DI you can throw that away and have a real 20 oz vertical refilable DI. It takes about 15 mimutes and maybe $5 in fittings. Every canister and filter cartridge in front of the RO membrane has an associated head loss so a single good sediment and DI beats multiples every time. Link to comment
GHill762 Posted December 11, 2012 Author Share Posted December 11, 2012 Stick with what you ordered for best performance and replumb the extra canister into a DI so if you now have a single DI you have dual DI or if you have little horizontal DI you can throw that away and have a real 20 oz vertical refilable DI.It takes about 15 mimutes and maybe $5 in fittings. Every canister and filter cartridge in front of the RO membrane has an associated head loss so a single good sediment and DI beats multiples every time. Dual DI? interesting.. but wouldn't I need a refillable DI cartridge to put in the canister? probably won't go this route but this is interesting.. would it be beneficial to have 2 RO membranes? I have ~430ppm tds at the tap, so if the membrane is a 95% rejection membrane, that is still ~20ppm tds after RO, if I add a second that would bring it down further right? or would that make the water flow way too ridiculously slow?? bahaha.. also just realized my "" came out as in my first post.. lol... Link to comment
AZDesertRat Posted December 11, 2012 Share Posted December 11, 2012 Yes you would need a refillable shell for about $5 or buy one prefilled with reef quality resin which can then be refilled for about $20. Dual membranes don't work like that. You don't run the permeate from one into another, it would require a booster pump to build it back up to 60+/- psi to force it through the second. Dual membranes take the brine or waste from the first to feed the second so the TDS is actually more concentrated in the second. You don't need a second membrane, 430 TDS is no big deal. Mine is always over 630 and as high as 850 depending on the seasons and blend. My RO only with a single sediment and single carbon gets that to between 2 and 3 TDS and my dual DI takes that to 0 TDS no sweat and for over a year per refill. If your membrane is only 95% you may be in need of a new membrane, mine is 99.43% and its over 4 years old already. Link to comment
GHill762 Posted December 11, 2012 Author Share Posted December 11, 2012 Yes you would need a refillable shell for about $5 or buy one prefilled with reef quality resin which can then be refilled for about $20. Dual membranes don't work like that. You don't run the permeate from one into another, it would require a booster pump to build it back up to 60+/- psi to force it through the second. Dual membranes take the brine or waste from the first to feed the second so the TDS is actually more concentrated in the second. You don't need a second membrane, 430 TDS is no big deal. Mine is always over 630 and as high as 850 depending on the seasons and blend. My RO only with a single sediment and single carbon gets that to between 2 and 3 TDS and my dual DI takes that to 0 TDS no sweat and for over a year per refill. If your membrane is only 95% you may be in need of a new membrane, mine is 99.43% and its over 4 years old already. I thought that was how they were rated. 90% rejection, 95% rejection etc. I thought I saw somewhere that RO membranes we use for reef setups are 95% rejection membranes.. meaning 5% of whatever comes through.. Link to comment
AZDesertRat Posted December 11, 2012 Share Posted December 11, 2012 A dry untested off the shelf Dow Filmtec 75 GPD RO membrane should be 96-98% rejection rate once broken in. Spectrapure takes Dow Filmtec RO membranes and treats them with a special proprietary process to improve their performance then depending on if its their normal or their Select series they either batch test them or individually hand test them for quality control and in the case of the Select series they guarantee them to be better than 98% rejection in writing. No other vendor offers this service that I am aware of and best of all their 90 GPD membranes still only sell for $35 for the batch tested and $45 for the hand tested and guaranteed versions. The worst possible membrane you could own is a 100 GPD Dow Filmtec which is not really a RO membrane but is considered a nano filter rated at only 90% rejection and according to the ANSI/NSF is for pool and spa use not drinking water due to its poorer performance. Link to comment
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