Just using DI water - good enough?

[loonz]

Hi,
Up till only recently I have always been using reef prime to "dechlorinize" my top-off water, but I noticed that of late bubbles have been appearing on my LR and red slime algae have been growing over some yellow polyps colony. Considering that nitrates are zero, dKH of about 11 thereabouts, I attributed the cause to buildup of phosphates or silicates.I bought a DI unit for SGD70, and the LFS told me its good for about 1600 litres(~423US gallons). Question is, is a DI unit good enough for maintaining phosphate-free water?Thanks for any inputs.

 

[randy holmes-farley]

A properly functioning DI will take out all phosphate. It will not, however, take out chloramine. You'll need carbon to take that out (or a chemical treatment) if you have it in your tap water.

 

[MattM]

DI only will remove more algae promoting nutrients than RO only.

The main advantage of RO/DI over DI only is the DI cartrige will last much. much longer in an RO/DI since it doesn't have to take the load of all the contaminants in the water.

 

[loonz]

Thanks, from what I gathered from your replies, DI only,if functioning properly, is actually better than an RO only. That is indeed reassuring!

 

[AnotherGoldenTeapot]

The only issue is the cost - the DI resin will expire much faster than if you have an RO stage feeding it.

For example if your RO stage was 90 efficient (and you'd be hoping for better than this) then the DI resin would last ten times longer between changes.

 

[Groucho]

Is the DI resin the same as the resin found in home water softeners?

 

[Anonymous]

hi.
no, but similar. Both are ion-exchange resin. The difference is that DI cation resin (or is it the anion resin, Randy?) exchanges positively charged ion with a proton (H+), while the cation resin in water softener exchange it with a sodium ion (Na+).

You can buy both type of resin from Kent Marine, but the water softener ion is not used in this hobby.

 

[sparks]

loonz - I've used DI for over 2 years now on my 6x2x2 and i've had no real problems with algeas etc. Considering i still have no DSB and run bios.
My phosphates are .25 ppm but whose is perfect, my nitrates are 20 Salifert kits.
I do have my DI connected after a charcoal under sink type filter until recently at least. Fresh DI water tested with the same kits are phosphates & nitrates both nil.
You will need to watch for expired resins, you can test this with an electronic resistance tester, just look for any readings between top and bottom or (water in or out) of the cartridge.
Any reading will most likely mean its expired.
Hope this helps a little.

 

[SPC]

Posted by Randy Holmes-Farley:
A properly functioning DI will take out all phosphate. It will not, however, take out chloramine. You'll need carbon to take that out (or a chemical treatment) if you have it in your tap water.

Randy, are you saying that our typical 4 or 5 stage RO/DI units do not remove chloramine?
I presume they remove chlorine, would you explain the difference please?
Steve

 

[Jawbone]

On another note is an RO filter good enough. no DI

 

[Anonymous]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> Randy, are you saying that our typical 4 or 5 stage RO/DI units do not remove chloramine?
I presume they remove chlorine, would you explain the difference please?
<hr></blockquote>

hi.
Almost all 5 stages unit have one or more carbon block prefilter before the RO. The carbon will remove the chloramine as well as chlorine (to prolong the life of the RO membrane), so you be fine with a 5 stages.

Without the carbon filter, the chloramine will pass thru the RO membrane since it is small enough and similar to water molecule. Since it is uncharged, the DI will not remove the chloramine. So carbon is sine qua non.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote

On another note is an RO filter good enough. no DI

It depends on what kind of water you started with. For soft water with very little charged ions, people oftentime can get away with just RO.

 

[MattM]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Jawbone:
<strong>On another note is an RO filter good enough. no DI</strong><hr></blockquote>

Depends a lot on where you live, i.e. what is the nature of your ion contaminents.

Here in New England, DI is a usually considered a must-have since we have relatively high silicates in our water and that is one of the ions not very efficiently removed by RO only.