RODI Producing 0 TDS but over 1ppm PO4

ChadmRoman

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I'm at a loss with this one. Two months ago, I sent in an ICP that for the first time registered 1.2ppm PO4. For the last 1.5 years I could barely keep PO4 above .01ppm. Long story extremely short, I traced it back to my RODI unit. I immediately replaced all four AL twist in cartridges, and still registered high PO4. I added three more DI canisters that follow BRS Parts 1-3, where 2 and 3 are supposed to strip out PO4, and a media reactor running seachem phosguard. Results still registering over 1ppm PO4, and I cannot for the life of me figure out why.

Measured tap, from RODI unit before container, and out of the container, all mixed with salt, not mixed with salt, and got the same results each time.

I feel like my tank is a ticking timebomb with this much PO4 going into it daily through the ATO. Any help or incite into this would be greatly appreciated.
 

blaxsun

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What kind of PO4 testing kit are you using? I’m not saying your numbers are off, but you could try a different test kit or have your LFS test you water as well. Might want to rule that out completely before having to switch to a new RO source for you water.

Something like TLF PhosBan might provide an interim solution to get your phosphates down (just read the instructions closely, dilute and use much less than the recommended dose to start).
 
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ChadmRoman

ChadmRoman

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Hanna UL Phosphate, keeps blinking .9 and lfs confirmed it as well around 1.2. I slept on it buying a new RODI unit. I think somethings wrong with the AL Twist in I’m using.
 

Tamberav

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Probably worth mentioning that the Hannah kit can not test pure RODI for phosphates and such accurately. It is not meant for pure water.

It needs the ions in it to work correctly. Like from our tanks/salt :) It will not give you an accurate reading.

The TDS could be zero because cheap TDS meters are just that. Cheap and they will have issues picking up phosphate in ultra pure water as well.

Remember, these are hobby grade tools and test kits.

If you buy a new RODI. I recommend getting a standard one and not those twist ones. A standard RODI can fit a wide range of media and not all media is equal. I love the spectrapure stuff and use a maxcap silica buster cartridge designed to remove silica, po4 and Nitrate before it hits the DI.
 
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blaxsun

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Hanna UL Phosphate, keeps blinking .9 and lfs confirmed it as well around 1.2. I slept on it buying a new RODI unit. I think somethings wrong with the AL Twist in I’m using.
I’d get a Salifert or similar kit and test again. I have a twist unit and it works flawlessly, and I believe you indicated the phosphates were high pre and post RODI?
 

Tamberav

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May I ask what exacetly this is? I added the BRS 3 part that is also supposed to remove PO4 and silica, but guess it's not work.

I can’t speak of the BRS stuff as I don’t use it. I am sure they work for many but definitely not as high quality as some other companies stuff that specialize in filtration. You generally get what you pay for as always. In house resin blend and pre pack perfectly based on hours of bench tests vs off the shelf bulk stuff you pack yourself that changes colors. Not saying it’s needed but everything has a different quality point.

This is what I use for my DI part. My TDS is 135ish (so pretty good) and it lasts me two years :)

The point of maxcap is to extend the life of the DI downstream.


Technically can’t be sure you rodi is the problem since you can’t use saltwater kits to test phosphate in ultra pure water. Mixing up fresh salt in clean bucket and test should work though.
 
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Tamberav

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I’d get a Salifert or similar kit and test again. I have a twist unit and it works flawlessly, and I believe you indicated the phosphates were high pre and post RODI?

You can’t use saltwater kits to test po4 in rodi. It won’t be accurate. They are not made to work with ultra pure water.
 

Reef.

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Remember your salt could contain PO4, I doubt as high as .1 though but could be that high in a duff batch.
 

blaxsun

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You can’t use saltwater kits to test po4 in rodi. It won’t be accurate. They are not made to work with ultra pure water.
I meant test your (fresh) saltwater mix with a different test kit. You’re using the ULR tester, right? I assume that means diluting similar to the Hanna nitrate ULR?
 

Tamberav

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I meant test your (fresh) saltwater mix with a different test kit. You’re using the ULR tester, right? I assume that means diluting similar to the Hanna nitrate ULR?
I think he meant he is testing po4 before it mixes. Tap and the RODI. I do think he tested the salt too though.
 

blaxsun

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I think he meant he is testing po4 before it mixes. Tap and the RODI. I do think he tested the salt too though.
The Hanna testers can sometimes give really bizarre readings, which is why I was just suggesting something like a cheap $10 Saliferrt (etc.) kit to rule out any problems with the tester itself.
 
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ChadmRoman

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Thanks everyone I took my rodi water in again to lfs who can test both fresh and saltwater and can confirm it’s over 1ppm with both tests.
Swapped out my rodi and did the same test at lfs and it showed .2. Thinking this result was from leftover water in the container. Thinking I’m back in business again.
 
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