When do I change my DO/Di filters?

NanoCube-boy · 03/02/2007, 06:09 PM

Hi, I'm new to RO/DI, well not excatly, but I don't know much about RO/DI filter system.

Anyways, when do, or how long I should change my filters?

My ten and one micron are looking dirty, but not my five mricon, but should I still change it anyways?
It's been over 12months since I change my filter, well since I installed my system.

From what I heard, I shouldn't change the DI and membrane unless my tds rise. RIGHT?

Fishbulb2 · 03/02/2007, 06:14 PM

typically change your prefilter every 6 months. Change your membrane once it starts getting worse than 96% rejection rate. Change your DI once you consistantly get a reading of 1 or more tds (depends how well calibrated your tds meter is. Basically change it once you get a consistant rise in tds).

The only exception to the prefilters that I would add is if you regularly test for chlorine breakthrough and use a pressure gauge to determine clogging. But since no one really ever checks for chlorine just replace them every 6 months and be safe.

FB

NanoCube-boy · 03/02/2007, 06:20 PM

Fishbulb2, Thanks. I'm sorry I don't understand what is prefilter? is it the 10, 5, one micron, membrane? What do you mean "Change your membrane once it starts getting worse than 96% rejection rate."? What is rejection rate? How can I tell that?

Fishbulb2 · 03/02/2007, 06:40 PM

The prefilters include both the sediment filters (white filters that look like wound threading) and the carbon filters (typically black bocks used to remove chlorine). THese two filters protect the membrane so that it lasts longer. Each component essentially protects the next component inline. I assume you have a 10 micron sediment filter and then two carbon filters, one being 5 and the other 1 micron. All three of these filters should be replaced between 6 months to a year.

The membrane is the true workhorse of the system it is the only component (other than the DI) to remove tds. The rejection rate is simply the % of tds that it blocks. A great membrane should block 98% of tds. A decent membrane will block about 96% tds. Lower than that and you should seriously consider replacing the membrane.

tap and ro refer to the tds of the tap water and ro only (no di)

[(tap-ro)/tap]*100 = membrane rejection %

FB

NanoCube-boy · 03/02/2007, 06:46 PM

[(tap-ro)/tap]*100 = membrane rejection %

tap ro tds read divided by tap tds read equal membrane rejection rate?

So i take ro water only and tap water tds, divide them both to get rejection rate results?

Fishbulb2 · 03/02/2007, 06:53 PM

first take the difference of the two. so subtract the ro only tds from the tap tds. Then divide this by the tap only tds. then multiply by 100.
example
tap tds = 425
ro only = 4 tds

[(425-4)/425]*100 = 99.05% rejection. Yay, this membrane would be a keeper!

FB

NanoCube-boy · 03/02/2007, 06:58 PM

I see. too bad I sold my tds meter... I have one built in only. so iono...hehe

03/02/2007, 06:09 PM	#1
NanoCube-boy Registered Member Join Date: Oct 2004 Location: San Francisco Posts: 1,930	When do I change my DO/Di filters? Hi, I'm new to RO/DI, well not excatly, but I don't know much about RO/DI filter system. Anyways, when do, or how long I should change my filters? My ten and one micron are looking dirty, but not my five mricon, but should I still change it anyways? It's been over 12months since I change my filter, well since I installed my system. From what I heard, I shouldn't change the DI and membrane unless my tds rise. RIGHT?

03/02/2007, 06:14 PM	#2
Fishbulb2 Registered Member Join Date: Mar 2006 Location: Bethesda, MD Posts: 1,807	typically change your prefilter every 6 months. Change your membrane once it starts getting worse than 96% rejection rate. Change your DI once you consistantly get a reading of 1 or more tds (depends how well calibrated your tds meter is. Basically change it once you get a consistant rise in tds). The only exception to the prefilters that I would add is if you regularly test for chlorine breakthrough and use a pressure gauge to determine clogging. But since no one really ever checks for chlorine just replace them every 6 months and be safe. FB __________________ Just getting back in, but trying to do it right! Current Tank Info: 40 gallon tank. SPS, LPS, few softies

03/02/2007, 06:40 PM	#4
Fishbulb2 Registered Member Join Date: Mar 2006 Location: Bethesda, MD Posts: 1,807	The prefilters include both the sediment filters (white filters that look like wound threading) and the carbon filters (typically black bocks used to remove chlorine). THese two filters protect the membrane so that it lasts longer. Each component essentially protects the next component inline. I assume you have a 10 micron sediment filter and then two carbon filters, one being 5 and the other 1 micron. All three of these filters should be replaced between 6 months to a year. The membrane is the true workhorse of the system it is the only component (other than the DI) to remove tds. The rejection rate is simply the % of tds that it blocks. A great membrane should block 98% of tds. A decent membrane will block about 96% tds. Lower than that and you should seriously consider replacing the membrane. tap and ro refer to the tds of the tap water and ro only (no di) [(tap-ro)/tap]*100 = membrane rejection % FB __________________ Just getting back in, but trying to do it right! Current Tank Info: 40 gallon tank. SPS, LPS, few softies

03/02/2007, 06:53 PM	#6
Fishbulb2 Registered Member Join Date: Mar 2006 Location: Bethesda, MD Posts: 1,807	first take the difference of the two. so subtract the ro only tds from the tap tds. Then divide this by the tap only tds. then multiply by 100. example tap tds = 425 ro only = 4 tds [(425-4)/425]*100 = 99.05% rejection. Yay, this membrane would be a keeper! FB __________________ Just getting back in, but trying to do it right! Current Tank Info: 40 gallon tank. SPS, LPS, few softies

03/02/2007, 06:20 PM	#3
NanoCube-boy Registered Member Join Date: Oct 2004 Location: San Francisco Posts: 1,930	Fishbulb2, Thanks. I'm sorry I don't understand what is prefilter? is it the 10, 5, one micron, membrane? What do you mean "Change your membrane once it starts getting worse than 96% rejection rate."? What is rejection rate? How can I tell that?

03/02/2007, 06:46 PM	#5
NanoCube-boy Registered Member Join Date: Oct 2004 Location: San Francisco Posts: 1,930	[(tap-ro)/tap]*100 = membrane rejection % tap ro tds read divided by tap tds read equal membrane rejection rate? So i take ro water only and tap water tds, divide them both to get rejection rate results?

03/02/2007, 06:58 PM	#7
NanoCube-boy Registered Member Join Date: Oct 2004 Location: San Francisco Posts: 1,930	I see. too bad I sold my tds meter... I have one built in only. so iono...hehe