rodi

jeddy576 · 12/31/2007, 02:03 PM

I am thinking about buying a rodi filter so i dont have to buy water from lfs anymore and i was wondering how do you know when to change the filters?

DanInSD · 12/31/2007, 02:51 PM

I got this one with a built-in TDS meter:

http://www.marinedepot.com/ps_ViewIt...ct~CP1343.html

You could go cheaper but this one is worth every penny. At least get clear canisters and color-changing DI resin. If you don't invest in an inline TDS (total dissolved solids) meter, get an external one.

You change the sediment filter and carbon block periodically -- I do it a few times a year. The sediment filter gets pretty gnarly pretty quickly in my area (a relatively new development in San Diego). We have "liquid rock" coming through the pipes -- some of the hardest water in the nation. Don't skimp on these -- the sediment filter is imperative for keeping crud out of the RO membrane, and the carbon filter gets rid of a lot of stuff like chlorine and chloramine that may well pass the rest of your filtration unaffected.

The RO filter should remain good for a long time, and you test that with TDS. The output of the RO should be less than about 30 ppm TDS. If it's more than this you need to change your RO membrane. Get a flush kit to increase longevity. I've had my unit for many years and it's still generating 15 ppm water.

You change the DI when your output TDS gets much above zero. You'll get plenty of warning as the resin becomes red. For me (about 30 gal/week) one cartridge lasts about 6-9 months.

Dan

unbreakable · 12/31/2007, 03:05 PM

usually every 6 months you change the filters and the membrane you change like every 2 years or something. DI resin is changed when it's exhaused; the tds meter will tell you or if it has color changing resin youll notice it

if youre looking for an ro/di save up your money for a good one with everything you need

the sponsor on here "the filter guys" has great service. everyone usually buys the ocean reef + 1 because it comes with everything you need including the tds meter. maybe you can look into it if you want

AZDesertRat · 12/31/2007, 03:22 PM

A handheld TDS meter is your best friend. It does not tell you when to replace the prefilter or carbon block but it does tell you when to change the membrane and DI cartridge. Pre and carbons need to be changed every 6 months and are pretty inexpensive even for high quality replacements. An RO membarne should last 3+ years or more providing you keep up with the prefilet rand carn=bon replacemenst and disinfect the housings when changing filters. Again a TDS meter will alert you to elevated TDS. Another indicator is reduced output or GPD due to fouling or plugging. I don't put any stock in flush valves as most people don't use them properly anyway. I have yet to see any conclusive proof they do anything at all other than lighten your wallet a few bucks. Keeping the waste ratio at 4:1 will do all the flushing you will ever need. My tap water TDS exceeds 800 and I never flush and still get maximum life out of my membranes because I use good quality replacement filters, keep up with the maintenance and maintain a 4:1 waste ratio. No one can give you a "should be less than about 30 ppm TDS" without knowing what your water is to begin with. My tap is 800 and I get 5.2 out of my RO only so 30 will kill me in DI resin, in fact 15 would too. What you want is 96-98% removal from whatever the tap water TDS is.

DI resin life is entirely dependent on how well your RO membrane is working and how much water you make. You can usually get a few months out of DI resin with normal use and its not too expensive to buy bulk resin replacements. Again the TDS meter is used to test the final effluent TDS. Iwould invest in a good handheld TDS meter and forget the inline type. The inlines are not as accurate and should be used a a guide only so you would need both anyway if you get the inline. I have two dual inlines and only use them as a spot check but get the handheld out when I really want to know the condition of things, they never agree.

Kentanner11 · 12/31/2007, 03:59 PM

If you are interested in purchasing one you can look at the sponsors page

I can't believe AZDesertRat forgot to mention his favorite unit is the SpectraPure unit. ;-P

You might also want to check out www.melevsreef.com he sells one as well.

(both are RC sponsors)

jeddy576 · 01/01/2008, 04:03 PM

how is this? http://www.buckeyefieldsupply.com/sh...ry=168&Sub=166

Kentanner11 · 01/01/2008, 04:15 PM

I'm not the expert (AZDesertRat is) but I am sure that is fine, but having a 5 stage system is even better!

AZDesertRat · 01/01/2008, 08:01 PM

The number of stages does not mean squat, its what the stages contain that counts. 4 is all you need for a good RO/DI system, a prefilter, good carbon block, 75 GPD membrane and a vertical DI filter.
A single 0.5 or 0.6 Matrix carbon block will outperform and outlast several 1, 5 or 10 micron blocks and dozens of granular cartridges.

I rate the 75 GPD as a Best Buy in my book due to its great value. Not many systems in that price range come with a good membrane, high quality cartridges, vertical refillable DI, inline pressure gauge, handheld TDS meter, adjustable flow restrictor (on request) and a flush valve. For myself I would probably replumb the flush valve into an RO bypass valve so I could use RO only for other purposes but thats just me. I have yet to se any documented proof flush valves do anything useful except give you a warm fuzzy. Keeping the waste ratio at 4:1 is really all you need for flushing action in almost all cases. My tap TDS is over 800 and I have never flushed a membrane yet in about 15 years now.

12/31/2007, 02:03 PM	#1
jeddy576 Premium Member Join Date: May 2006 Location: Olympia, Wa Posts: 116	rodi I am thinking about buying a rodi filter so i dont have to buy water from lfs anymore and i was wondering how do you know when to change the filters?

12/31/2007, 03:05 PM	#3
unbreakable D: Join Date: May 2007 Location: ? Posts: 2,868	usually every 6 months you change the filters and the membrane you change like every 2 years or something. DI resin is changed when it's exhaused; the tds meter will tell you or if it has color changing resin youll notice it if youre looking for an ro/di save up your money for a good one with everything you need the sponsor on here "the filter guys" has great service. everyone usually buys the ocean reef + 1 because it comes with everything you need including the tds meter. maybe you can look into it if you want __________________ INTERNET= Serious Business!

12/31/2007, 03:59 PM	#5
Kentanner11 Registered Member Join Date: Apr 2007 Location: Phoenix Posts: 1,956	If you are interested in purchasing one you can look at the sponsors page I can't believe AZDesertRat forgot to mention his favorite unit is the SpectraPure unit. ;-P You might also want to check out www.melevsreef.com he sells one as well. (both are RC sponsors) __________________ - Tanner Current Tank Info: RSM 34g

01/01/2008, 04:15 PM	#7
Kentanner11 Registered Member Join Date: Apr 2007 Location: Phoenix Posts: 1,956	I'm not the expert (AZDesertRat is) but I am sure that is fine, but having a 5 stage system is even better! __________________ - Tanner Current Tank Info: RSM 34g

12/31/2007, 02:51 PM	#2
DanInSD Registered Member Join Date: Jun 2005 Posts: 1,255	I got this one with a built-in TDS meter: http://www.marinedepot.com/ps_ViewIt...ct~CP1343.html You could go cheaper but this one is worth every penny. At least get clear canisters and color-changing DI resin. If you don't invest in an inline TDS (total dissolved solids) meter, get an external one. You change the sediment filter and carbon block periodically -- I do it a few times a year. The sediment filter gets pretty gnarly pretty quickly in my area (a relatively new development in San Diego). We have "liquid rock" coming through the pipes -- some of the hardest water in the nation. Don't skimp on these -- the sediment filter is imperative for keeping crud out of the RO membrane, and the carbon filter gets rid of a lot of stuff like chlorine and chloramine that may well pass the rest of your filtration unaffected. The RO filter should remain good for a long time, and you test that with TDS. The output of the RO should be less than about 30 ppm TDS. If it's more than this you need to change your RO membrane. Get a flush kit to increase longevity. I've had my unit for many years and it's still generating 15 ppm water. You change the DI when your output TDS gets much above zero. You'll get plenty of warning as the resin becomes red. For me (about 30 gal/week) one cartridge lasts about 6-9 months. Dan

12/31/2007, 03:22 PM	#4
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	A handheld TDS meter is your best friend. It does not tell you when to replace the prefilter or carbon block but it does tell you when to change the membrane and DI cartridge. Pre and carbons need to be changed every 6 months and are pretty inexpensive even for high quality replacements. An RO membarne should last 3+ years or more providing you keep up with the prefilet rand carn=bon replacemenst and disinfect the housings when changing filters. Again a TDS meter will alert you to elevated TDS. Another indicator is reduced output or GPD due to fouling or plugging. I don't put any stock in flush valves as most people don't use them properly anyway. I have yet to see any conclusive proof they do anything at all other than lighten your wallet a few bucks. Keeping the waste ratio at 4:1 will do all the flushing you will ever need. My tap water TDS exceeds 800 and I never flush and still get maximum life out of my membranes because I use good quality replacement filters, keep up with the maintenance and maintain a 4:1 waste ratio. No one can give you a "should be less than about 30 ppm TDS" without knowing what your water is to begin with. My tap is 800 and I get 5.2 out of my RO only so 30 will kill me in DI resin, in fact 15 would too. What you want is 96-98% removal from whatever the tap water TDS is. DI resin life is entirely dependent on how well your RO membrane is working and how much water you make. You can usually get a few months out of DI resin with normal use and its not too expensive to buy bulk resin replacements. Again the TDS meter is used to test the final effluent TDS. Iwould invest in a good handheld TDS meter and forget the inline type. The inlines are not as accurate and should be used a a guide only so you would need both anyway if you get the inline. I have two dual inlines and only use them as a spot check but get the handheld out when I really want to know the condition of things, they never agree.

01/01/2008, 04:03 PM	#6
jeddy576 Premium Member Join Date: May 2006 Location: Olympia, Wa Posts: 116	how is this? http://www.buckeyefieldsupply.com/sh...ry=168&Sub=166

01/01/2008, 08:01 PM	#8
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	The number of stages does not mean squat, its what the stages contain that counts. 4 is all you need for a good RO/DI system, a prefilter, good carbon block, 75 GPD membrane and a vertical DI filter. A single 0.5 or 0.6 Matrix carbon block will outperform and outlast several 1, 5 or 10 micron blocks and dozens of granular cartridges. I rate the 75 GPD as a Best Buy in my book due to its great value. Not many systems in that price range come with a good membrane, high quality cartridges, vertical refillable DI, inline pressure gauge, handheld TDS meter, adjustable flow restrictor (on request) and a flush valve. For myself I would probably replumb the flush valve into an RO bypass valve so I could use RO only for other purposes but thats just me. I have yet to se any documented proof flush valves do anything useful except give you a warm fuzzy. Keeping the waste ratio at 4:1 is really all you need for flushing action in almost all cases. My tap TDS is over 800 and I have never flushed a membrane yet in about 15 years now.