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View Full Version : what the heck is wrong with my DI?


mcliffy2
03/23/2008, 09:43 AM
I changed my DI resin one week ago. Yesterday I'm making 0 TDS water, all the sudden today its 14 TDS. And the water coming out of my RO is 2 TDS. I need to make water and am just using the 2 TDS RO only water for now, but the heck gives? Sometimes there is an initial burst of high TDS water then it comes down, but I ran it for about 15 minutes through the DI, and it was still coming out 15 TDS. Did I just get a bad batch of DI or something? But if that is the problem how was I getting 0 TDS yesterday?

Randy Holmes-Farley
03/23/2008, 11:22 AM
What brand of DI resin?

How did you measure the TDS?

mcliffy2
03/23/2008, 03:00 PM
Its DI resin from bulkreefsupply.com...never had a problem with it before. I'm measuring my TDS using a Hanna handheld TDS meter. I haven't calibrated recently but its fairly new, and my tap water is pretty consistent at 152-154, so I usually just "calibrate" off that.

rbursek
03/23/2008, 03:24 PM
You have to calibrate with a 2 test solutions from Hanna, one is usually about 5 and thee other around 10.

mcliffy2
03/23/2008, 03:30 PM
I'm pretty sure the calibration is not off though, because I am getting 2 TDS out of my RO membranes when I unhook them from the DI. Then I hook it back up to the DI and its 15 TDS. Even if the calibration were off, its clear the TDS is going up after the DI, and I've probably only made about 75 gallons of water since I replaced the DI last week.

rbursek
03/23/2008, 03:32 PM
Sorry, that is the solution for a Hanna PH hand held, I have no experience with there TDS meter, Da. Someone will chime in here.

Randy Holmes-Farley
03/23/2008, 04:15 PM
I'm not sure why that would happen, aside from the DI not packing well, or being partially spent before used by you.

My concern is not the calibration per se, but whether there might be contamination in the solution that you collect. A tiny bit of salt contamination goes a long way.

mcliffy2
03/23/2008, 06:35 PM
What do you mean by the DI not packing well? I'm not familiar with this...

mcliffy2
03/23/2008, 07:11 PM
ok, I took a guess at packing, and read a bit online. Found out you are supposed to pack in the DI tightly, which I did not when replacing it. I threw out the DI and refilled it, this time packing it very tightly. TDS is back down, but I'd like to know if the failure to pack it caused this...I cant afford to refill my DI every week :)

mcliffy2
03/23/2008, 07:11 PM
double post

Randy Holmes-Farley
03/24/2008, 06:21 AM
Yes, if you fill the cartridge with resin in such a way that water can flow through without interacting with the beads, then you may get poor performance. This is called channeling. If it interacted with only one of the resin types well, instead of both, then the effluent pH could be very high or low in pH and actually rise in measured TDS.

mcliffy2
03/24/2008, 06:56 AM
ok, so it was a $10 lesson learned (a canister of DI resin), cheap as they come in reefkeeping. Thanks Randy.

Randy Holmes-Farley
03/24/2008, 08:41 AM
You're welcome. I hope it works better going forward!

Happy Reefing. :)

mcliffy2
03/24/2008, 09:21 AM
Oh one follow up. What technique do you use for packing your DI...I just used the bottom of a non-tapered shot glass and periodically packed it in. I'm guessing there is something better out there...

Thanks again.

Randy Holmes-Farley
03/24/2008, 09:56 AM
I buy pre-made DI cartridges. :)

mcliffy2
03/24/2008, 10:02 AM
Ah - well, when this DI runs out, I may look into that. Changing them out is a nasty job, and seems like it is prone to error.

AZDesertRat
03/24/2008, 10:28 AM
I have it on good authority there is some bad or low quality DI resin on the market right now. I have seen some really disappointing test results from resins bought from different suppliers. Some of it I purchased myself.

To pack a vertical DI cartridge, fill it to the top, tap it on the tabletop several times to pack it down, fill it to the top again, tap it on the table or counter several times again, top it up, repeat, then install the foam ring on top and screw it together. resin shrinks slightly with use so this will ensure it stays packed tightly and you do not get channeling or short circuiting.

I also buy prefilled DI cartridges as I found bulk resins just did not give me the resin life or final effluent quality I needed.

Billybeau1
03/24/2008, 05:35 PM
<a href=showthread.php?s=&postid=12165481#post12165481 target=_blank>Originally posted</a> by AZDesertRat
I also buy prefilled DI cartridges as I found bulk resins just did not give me the resin life or final effluent quality I needed.

And with the tds of your water, you would know. :D

AZDesertRat
03/25/2008, 07:49 AM
HEY......Rub it in why don'tcha!

Billybeau1
03/25/2008, 02:18 PM
:lol:

I got that Com-100 you recommended. It is quite an amazing instrument. Thanks for the tip.

I still like my dual in-line though. I have trouble getting the glass squeaky clean to test my water with the Com. :D