1 week old RO/DI Numbers

OldSchoolNewbie · 04/10/2007, 04:44 AM

I have had my RO/DI unit running for a week now. Tested tap water at 238 ppm, water from RO/DI tested @ 13 ppm. Are these numbers any good ... I was told in my previous thread that my el-cheapo unit would never see 0 ppm (advertised @ 0ppm) ... However 13 ppm is a darn site better than 238 ppm, dont ya think ?

HowardW · 04/10/2007, 05:44 AM

Well a TDS of 13 from the RO side only isn't too bad and about 94.5% rejection rate, but if that reading is coming from the DI part too then your DI isn't working.

DrBDC · 04/10/2007, 05:47 AM

You can get 0 tds out of a cheap unit. You can get 0 out of just a di cartridge. It will just use more di resin. I change my di resin when the tds hits 1. If you have a horizontal di unit, add on a vertical one and keep an eye on the numbers.

David Grigor · 04/10/2007, 10:28 AM

13ppm coming out of the membrane is just okay. Expect your replace resin costs to be double or triple that of using a 98% rejection rate membrane.

If 13ppm is after the DI, your DI needs replaced already.

Are you using an inline TDS meter or handheld to get that reading. If using handheld be sure to use a clean glass and rinse several times in RO/DI water before testing. Not doing so, your reading could be higher just from the container your testing with.

04/10/2007, 04:44 AM	#1
OldSchoolNewbie Registered Member Join Date: Feb 2007 Location: Indiana Posts: 68	1 week old RO/DI Numbers I have had my RO/DI unit running for a week now. Tested tap water at 238 ppm, water from RO/DI tested @ 13 ppm. Are these numbers any good ... I was told in my previous thread that my el-cheapo unit would never see 0 ppm (advertised @ 0ppm) ... However 13 ppm is a darn site better than 238 ppm, dont ya think ? __________________ JTCCB (jebo tuners club for cheap bastards) "Live each day like it is your last, because, someday it will be" "Watch Him Folks He's A Fairly Dangerous Man" Current Tank Info: 58g Oceanic RR, Odyssea 36" 442W

04/10/2007, 05:44 AM	#2
HowardW Registered Member Join Date: Feb 2006 Location: Aurora, IL Posts: 1,763	Well a TDS of 13 from the RO side only isn't too bad and about 94.5% rejection rate, but if that reading is coming from the DI part too then your DI isn't working. __________________ Florida live rock addict

04/10/2007, 05:47 AM	#3
DrBDC Registered Member Join Date: Aug 2004 Location: Ballwin, Missouri Posts: 10,358	You can get 0 tds out of a cheap unit. You can get 0 out of just a di cartridge. It will just use more di resin. I change my di resin when the tds hits 1. If you have a horizontal di unit, add on a vertical one and keep an eye on the numbers. __________________ Some drink at the fountain of knowledge, some just gargle, but most are rabid. Current Tank Info: 180g sps+75 softy/lps on one system tunze's, seio's, mjmods, aquacontroller w/add ons, 2X400 XM10000 and 3X160 vho actinic, 110g sump, 110 frag tank, Geo Beckett and other stuff

04/10/2007, 10:28 AM	#4
David Grigor Registered Member Join Date: Jan 2000 Location: Brooklyn Center, MN USA Posts: 4,951	13ppm coming out of the membrane is just okay. Expect your replace resin costs to be double or triple that of using a 98% rejection rate membrane. If 13ppm is after the DI, your DI needs replaced already. Are you using an inline TDS meter or handheld to get that reading. If using handheld be sure to use a clean glass and rinse several times in RO/DI water before testing. Not doing so, your reading could be higher just from the container your testing with. __________________ Neptune Systems 2016 Marine Aquarium Hobbyist of the Year Current Tank Info: 180g mixed reef show tank