RO/DI filter change recommendations

jb61264 · 07/07/2009, 10:28 PM

Just bought a used Coralife 4-stage 50 gpd RO/DI unit that had been used for about 6 months. Ran some water through it and had a TDS reading of about 70 so I am guessing I need to change one or all of the filters.

Do I need to change "all" of the filters at once or can I for instance change out the carbon block cartridge and mixed bed resin cartridge and see if that gets me down to 0 TDS? There is also a micron filter cartridge and then the "tfc membrane"..but from what little I understand or know about RO/DI units at this time, I read that the TFC membrane only needs replacing every 2-3 years.

Would appreciate any recommendations...should I just replace all three cartridges or just one of them (resin cartridge)?

dots · 07/08/2009, 12:28 AM

I would buy a filter replacment package and replace them all at the same time. This will ensure you are starting off with a clean slate, that if you replace a filter downstream from a dirty filter that may leach it would prematurly wear.

Given anything that makes it through ends up in the tank, I wouldn't take any chances.

http://www.bulkreefsupply.com/index.html

http://www.spectrapure.com/

http://www.thefilterguys.biz/index.htm

boret · 07/08/2009, 12:39 AM

I agree with dots, might as well change all three. You could also get an extra set, you will replace them within a year and you can save on shipping.
Also, if the used RODI unit has been sitting for a while and the membrane dried up it could have gone bad. How do you measure TDS? I have a dual TDS meter and get a reading after the filters and another one after the DI. That way I can see which one is going bad.

One more thing, you might want to run the unit for a full day and then measure the TDS. Some units can be flushed, check if yours can.

I would add to the list of vendors these guys (airwaterice.com)
LINK

jb61264 · 07/08/2009, 01:03 AM

Thanks for the input dots and boret...I think I will just go ahead and replace the three filters. The unit had not been sitting for a while at all and in fact had water in it when I brought it home. I only ran it for about an hour to get some water and measured with a handheld TDS meter...running for 24 hours and measuring again sounds like a great idea

thorsky · 07/08/2009, 10:24 AM

jb, what's your input water TDS look like? I would check that, then check the water coming from the membrane (no DI) and make sure you are seeing at least 90% rejection. Not sure what membrane you have but 90% rejection would be bare minimum if it was me. 70TDS post membrane sounds very high, and changing out all your sediment filters wont help if the membrane is toast.

jb61264 · 07/08/2009, 03:41 PM

thorsky, the input water TDS was about 210ppm

boret · 07/08/2009, 04:08 PM

What's the TDS after running it for a day?

thorsky · 07/08/2009, 07:04 PM

Interested in the "after a day" results as well, but from what I've found after a few gallons your TDS doesn't change much. At 210 in and 70 out, I'd be very suspect of the membrane. That's about 67% rejection if my math skills are intact. You are checking the TDS right after the membrane and before the DI correct? A batch of spent DI can leach TDS back in that's the only reason I ask.

If the membrane is toast, I'd go to Spectrapure for a new one. They are pricey but their quality is top notch. I switched to all Spectrapure stuff about a year ago and have had great luck. To be fair I've also used TheFilterGuys and PurelyH20 and their stuff was very good.

boret · 07/08/2009, 07:52 PM

To give you an idea, mine measures 3 after membrane, 0 at final output. I have about 125-150 tds if I measure tap water.
When I first turn the unit I get a reading of about 45-50 at both. After a few minutes it goes down to the 3-0 reading.

I keep my RODI in a 35g reservoir and only turn on the water to the RODI unit when is down to about ~15 gallons. That way the RODI runs a full 20 gallons. I used to rely only on the back pressure valve to refill the tank but it just kept opening and closing the flow of water every few minutes and gave me RODI water with high TDS.

I also have a float sensor that will send me an email through the Aqua Controller when the level is low in the RODI so I manually open the little water valve and it refills.

I am thinking about using a solenoid to open and close with the sensor. Anyway, I just thought I would share my RODI experiences now that you have the unit.

I bought mine used as well and I just went ahead and put new ones in of everything. That way I can keep track of it instead of relying on the guesstimate of the guy that sold it to me.

thorsky · 07/08/2009, 08:01 PM

Quote:

Originally posted by boret
I also have a float sensor that will send me an email through the Aqua Controller when the level is low in the RODI so I manually open the little water valve and it refills.

That is very cool! Love the geek factor. Someday I hope to have full web enabled control...just gotta wrestle the credit card away from the wife.

boret · 07/08/2009, 08:26 PM

Yeah...LOL talk about geek factor. I love the Aqua Controller, check out my signature in my local club forum:

jb61264 · 07/08/2009, 11:01 PM

hey guys...i'm going to find a different fitting for my faucet tomorrow during lunch and then I'm going to run this thing for 24 hours and retake my TDS readings..will post on Friday

jb61264 · 07/09/2009, 04:51 PM

ok...well after letting the RO/DI run for about 8 hours, the water is coming out at 12ppm...the wastewater is 380ppm and the water in from the tap is 280 (if that makes any sense)

At what point in ppm should you "stop" using the RO/DI from your system...I realize we probably want 0ppm but am wondering where the upper level is for water that can be considered useable for a reef system

thorsky · 07/09/2009, 08:51 PM

So you are getting a TDS of 12 post RO pre DI? If that's the case, what's the TDS after DI? 280 in, 12 out from just the membrane is good.

jb61264 · 07/09/2009, 10:21 PM

The TDS is 12 after the entire system...after RO and DI it is 12....the stuff I get from a local grocery store that uses a 7 step fancy system is 2ppm.

At what point should reefers stop using RO/DI?...at what ppm?

sjm817 · 07/09/2009, 11:13 PM

It should be 0 after the whole system. What is it after the RO before the DI?

jb61264 · 07/09/2009, 11:47 PM

i don't have an inline meter...there are three cannisters on my setup and i am just measuring what goes in and what comes out...although i did measure the "wastewater" line coming out of the system...it was higher than the tapwater going into the system.

I figured it should be zero after the entire system but wondered if there is a level at which you can still use the RO/DI without adverse effects on your water quality.

I'll be ordering new filters from bulkreefsupply this weekend (they seem to have the best pricing on stuff as far as the comparisons i've done so far)

sjm817 · 07/09/2009, 11:57 PM

TDS of 12 with a tap of 280 seems reasonable for the RO. It sounds like you need to change out the DI. I would not use water with a TDS of 12.

jb61264 · 07/10/2009, 12:05 AM

Thanks for the reply...think I'll get my order in to BRS tomorrow and use the 7 stage RO/DI from the grocery store until I get my stuff in for my RO/DI

07/07/2009, 10:28 PM	#1
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	RO/DI filter change recommendations Just bought a used Coralife 4-stage 50 gpd RO/DI unit that had been used for about 6 months. Ran some water through it and had a TDS reading of about 70 so I am guessing I need to change one or all of the filters. Do I need to change "all" of the filters at once or can I for instance change out the carbon block cartridge and mixed bed resin cartridge and see if that gets me down to 0 TDS? There is also a micron filter cartridge and then the "tfc membrane"..but from what little I understand or know about RO/DI units at this time, I read that the TFC membrane only needs replacing every 2-3 years. Would appreciate any recommendations...should I just replace all three cartridges or just one of them (resin cartridge)? __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL

07/08/2009, 12:28 AM	#2
dots Registered Member Join Date: Nov 2004 Location: Sacramento, CA Posts: 6,258	I would buy a filter replacment package and replace them all at the same time. This will ensure you are starting off with a clean slate, that if you replace a filter downstream from a dirty filter that may leach it would prematurly wear. Given anything that makes it through ends up in the tank, I wouldn't take any chances. http://www.bulkreefsupply.com/index.html http://www.spectrapure.com/ http://www.thefilterguys.biz/index.htm __________________ ~Doug

07/08/2009, 12:39 AM	#3
boret Premium Member Join Date: Apr 2008 Location: Fairfax, VA - USA Posts: 548	I agree with dots, might as well change all three. You could also get an extra set, you will replace them within a year and you can save on shipping. Also, if the used RODI unit has been sitting for a while and the membrane dried up it could have gone bad. How do you measure TDS? I have a dual TDS meter and get a reading after the filters and another one after the DI. That way I can see which one is going bad. One more thing, you might want to run the unit for a full day and then measure the TDS. Some units can be flushed, check if yours can. I would add to the list of vendors these guys (airwaterice.com) LINK __________________ Reef Central Corner Club. Visit my Home Page for build thread. Current Tank Info: 92g Corner Reef Tank

07/08/2009, 01:03 AM	#4
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	Thanks for the input dots and boret...I think I will just go ahead and replace the three filters. The unit had not been sitting for a while at all and in fact had water in it when I brought it home. I only ran it for about an hour to get some water and measured with a handheld TDS meter...running for 24 hours and measuring again sounds like a great idea __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL

07/08/2009, 03:41 PM	#6
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	thorsky, the input water TDS was about 210ppm __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL

07/08/2009, 10:24 AM	#5
thorsky Registered Member Join Date: Nov 2003 Location: Rhode Island Posts: 407	jb, what's your input water TDS look like? I would check that, then check the water coming from the membrane (no DI) and make sure you are seeing at least 90% rejection. Not sure what membrane you have but 90% rejection would be bare minimum if it was me. 70TDS post membrane sounds very high, and changing out all your sediment filters wont help if the membrane is toast.

07/08/2009, 04:08 PM	#7
boret Premium Member Join Date: Apr 2008 Location: Fairfax, VA - USA Posts: 548	What's the TDS after running it for a day? __________________ Reef Central Corner Club. Visit my Home Page for build thread. Current Tank Info: 92g Corner Reef Tank

07/08/2009, 07:04 PM	#8
thorsky Registered Member Join Date: Nov 2003 Location: Rhode Island Posts: 407	Interested in the "after a day" results as well, but from what I've found after a few gallons your TDS doesn't change much. At 210 in and 70 out, I'd be very suspect of the membrane. That's about 67% rejection if my math skills are intact. You are checking the TDS right after the membrane and before the DI correct? A batch of spent DI can leach TDS back in that's the only reason I ask. If the membrane is toast, I'd go to Spectrapure for a new one. They are pricey but their quality is top notch. I switched to all Spectrapure stuff about a year ago and have had great luck. To be fair I've also used TheFilterGuys and PurelyH20 and their stuff was very good.

07/08/2009, 07:52 PM	#9
boret Premium Member Join Date: Apr 2008 Location: Fairfax, VA - USA Posts: 548	To give you an idea, mine measures 3 after membrane, 0 at final output. I have about 125-150 tds if I measure tap water. When I first turn the unit I get a reading of about 45-50 at both. After a few minutes it goes down to the 3-0 reading. I keep my RODI in a 35g reservoir and only turn on the water to the RODI unit when is down to about ~15 gallons. That way the RODI runs a full 20 gallons. I used to rely only on the back pressure valve to refill the tank but it just kept opening and closing the flow of water every few minutes and gave me RODI water with high TDS. I also have a float sensor that will send me an email through the Aqua Controller when the level is low in the RODI so I manually open the little water valve and it refills. I am thinking about using a solenoid to open and close with the sensor. Anyway, I just thought I would share my RODI experiences now that you have the unit. I bought mine used as well and I just went ahead and put new ones in of everything. That way I can keep track of it instead of relying on the guesstimate of the guy that sold it to me. __________________ Reef Central Corner Club. Visit my Home Page for build thread. Current Tank Info: 92g Corner Reef Tank

07/08/2009, 08:26 PM	#11
boret Premium Member Join Date: Apr 2008 Location: Fairfax, VA - USA Posts: 548	Yeah...LOL talk about geek factor. I love the Aqua Controller, check out my signature in my local club forum: __________________ Reef Central Corner Club. Visit my Home Page for build thread. Current Tank Info: 92g Corner Reef Tank

07/08/2009, 11:01 PM	#12
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	hey guys...i'm going to find a different fitting for my faucet tomorrow during lunch and then I'm going to run this thing for 24 hours and retake my TDS readings..will post on Friday __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL

07/09/2009, 04:51 PM	#13
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	ok...well after letting the RO/DI run for about 8 hours, the water is coming out at 12ppm...the wastewater is 380ppm and the water in from the tap is 280 (if that makes any sense) At what point in ppm should you "stop" using the RO/DI from your system...I realize we probably want 0ppm but am wondering where the upper level is for water that can be considered useable for a reef system __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL

07/09/2009, 08:51 PM	#14
thorsky Registered Member Join Date: Nov 2003 Location: Rhode Island Posts: 407	So you are getting a TDS of 12 post RO pre DI? If that's the case, what's the TDS after DI? 280 in, 12 out from just the membrane is good.

07/09/2009, 10:21 PM	#15
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	The TDS is 12 after the entire system...after RO and DI it is 12....the stuff I get from a local grocery store that uses a 7 step fancy system is 2ppm. At what point should reefers stop using RO/DI?...at what ppm? __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL Last edited by jb61264; 07/09/2009 at 10:31 PM.

07/09/2009, 11:13 PM	#16
sjm817 On Yer left! Join Date: Sep 2004 Location: Northern VA Posts: 18,777	It should be 0 after the whole system. What is it after the RO before the DI? __________________ - Scott

07/09/2009, 11:47 PM	#17
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	i don't have an inline meter...there are three cannisters on my setup and i am just measuring what goes in and what comes out...although i did measure the "wastewater" line coming out of the system...it was higher than the tapwater going into the system. I figured it should be zero after the entire system but wondered if there is a level at which you can still use the RO/DI without adverse effects on your water quality. I'll be ordering new filters from bulkreefsupply this weekend (they seem to have the best pricing on stuff as far as the comparisons i've done so far) __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL

07/09/2009, 11:57 PM	#18
sjm817 On Yer left! Join Date: Sep 2004 Location: Northern VA Posts: 18,777	TDS of 12 with a tap of 280 seems reasonable for the RO. It sounds like you need to change out the DI. I would not use water with a TDS of 12. __________________ - Scott

07/10/2009, 12:05 AM	#19
jb61264 Registered Member Join Date: Jan 2008 Location: Planet Earth Posts: 1,112	Thanks for the reply...think I'll get my order in to BRS tomorrow and use the 7 stage RO/DI from the grocery store until I get my stuff in for my RO/DI __________________ In the end (and the begining) we're all just stardust anyway... Current Tank Info: 75 gallon SPS reef/55 gallon sump/6x54W TEK T5HO/Reef Octopus 200 Extreme Skimmer/Reef Octopus Single Chamber Calcium Reactor/RKL