When to Change RO/DI Filters.

mike810 · 07/01/2010, 09:50 PM

My ro/di unit is literally only a few months old. I installed a dual TDS meter a couple months ago. The output after the DI canister read zero at the time. It is now reading 1PPM. At what ppm after the DI should I watch out for?

I don't use this unit to make drinking water. I only use it to make water for top offs and water changes. My tank is only a 65G and I do 10% W/C a week. So I really haven't put the unit under much use.

crichard6069 · 07/02/2010, 05:10 AM

I believe this depends on your water quality itself.. Granted, I don't have a ton of experience or anything with an RO/DI unit (my typhoon has only been up for about a month or so) but I've read on forums anywhere between 2 - 5 ppm on your TDS..

Tagging along on this for my own info (always being selfish thinking of myself!)

sedor · 07/02/2010, 06:12 AM

Keep in mind that when the tds meter is reading even 1 it is because some part of the filtration process is exhausted. Unless your source water is so bad that your always seeing a number above 0, I would just go ahead and change the prefilters and the DI resin now. Its job is to output 0 TDS.

mike810 · 07/02/2010, 11:45 AM

I was measuring around 250 something TDS water going in. For a few months, water going out read 0 TDS. I thought the TDS levels going in was normal. Do ro filters usually exhaust itself within a few months?

PurdueWaterGuy · 07/02/2010, 02:42 PM

The RO membrane can last for years if you treat it properly. The DI resin has a fixed capacity to absorb ions and it's lifespan will vary according to your source water and how you pre-treat it.

A lot of reefers copy what we do in big scale systems - put two DI's in series and watch the TDS on the output of the first one. When it gets to some predetermined value, like 5 ppm TDS, you remove the lead resin, move the lag into the lead postion, and install a new DI in the lag position. That way you always have good water going to your tank, and you make sure the resin is spent before it gets replaced.

Make sense?

Tim

@ home, 90 gallon tank, dry, waiting for the remodelling to be over
@ work, 19,000 gallon per day RO

07/01/2010, 09:50 PM	#1
mike810 Registered Member Join Date: Feb 2010 Location: Huntington Beach Posts: 2,235	When to Change RO/DI Filters. My ro/di unit is literally only a few months old. I installed a dual TDS meter a couple months ago. The output after the DI canister read zero at the time. It is now reading 1PPM. At what ppm after the DI should I watch out for? I don't use this unit to make drinking water. I only use it to make water for top offs and water changes. My tank is only a 65G and I do 10% W/C a week. So I really haven't put the unit under much use. Last edited by mike810; 07/01/2010 at 09:52 PM. Reason: forgot to mention.

07/02/2010, 06:12 AM	#3
sedor Registered Member Join Date: Sep 2007 Location: Charlotte, NC Posts: 4,689	Keep in mind that when the tds meter is reading even 1 it is because some part of the filtration process is exhausted. Unless your source water is so bad that your always seeing a number above 0, I would just go ahead and change the prefilters and the DI resin now. Its job is to output 0 TDS. __________________ Ryan

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07/02/2010, 05:10 AM	#2
crichard6069 Registered Member Join Date: Jul 2003 Location: Western Massachusetts Posts: 591	I believe this depends on your water quality itself.. Granted, I don't have a ton of experience or anything with an RO/DI unit (my typhoon has only been up for about a month or so) but I've read on forums anywhere between 2 - 5 ppm on your TDS.. Tagging along on this for my own info (always being selfish thinking of myself!)

07/02/2010, 11:45 AM	#4
mike810 Registered Member Join Date: Feb 2010 Location: Huntington Beach Posts: 2,235	I was measuring around 250 something TDS water going in. For a few months, water going out read 0 TDS. I thought the TDS levels going in was normal. Do ro filters usually exhaust itself within a few months?

07/02/2010, 02:42 PM	#5
PurdueWaterGuy Registered Member Join Date: May 2010 Location: Lafayette, IN Posts: 196	The RO membrane can last for years if you treat it properly. The DI resin has a fixed capacity to absorb ions and it's lifespan will vary according to your source water and how you pre-treat it. A lot of reefers copy what we do in big scale systems - put two DI's in series and watch the TDS on the output of the first one. When it gets to some predetermined value, like 5 ppm TDS, you remove the lead resin, move the lag into the lead postion, and install a new DI in the lag position. That way you always have good water going to your tank, and you make sure the resin is spent before it gets replaced. Make sense? Tim @ home, 90 gallon tank, dry, waiting for the remodelling to be over @ work, 19,000 gallon per day RO