phosphate in DI water?

[no_wedge]

i tested my 0tds di water for phosphates using my API phosphate test, and it shows what looks like .5 or 1 ppm of phosphate, is this possible, or just a fluke since the water is pure?

 

[aquaknight]

How old is the RO/DI unit, and what exactly are you measuring TDS with (make/model reader)?
RO membranes are very effective at removing phosphates, and in the extremely unlikely event they happen to get past the RO, the DI section would remove them. How old is the API test kit? I suspect a bad test kit if the RO/DI unit checks out.

 

[aquaknight]

Additional thought, how long after you made the water did you test for phosphates? And if not immediately, what are you storing the water in? It's not an uncommon occurrence for something like a garbage can to leach phosphates.

 

[no_wedge]

it was right out of the di hose as it was being destributed.
The Unit has all brand new filters, 1 micron sediment, CGAC cartridge, .6 Carbon block, 75g Filmtec RO, and then di.
The API test kit is a year old. and the liquid kind

 

[ajroc31]

Phosphate tests are not very reliable. I just hope that you did not kill your RO unit when you were making the changes. Make sure you have correct temp of the water, or it will go too fast and not catch everything. In addition it could damage the membrane.

 

[acrylic51]

Water temp will affect your production rate no really your phosphate level. Your membrane will only process a certain amount of water and that is dependable on several things....1 being water pressure, 2 water temp and your flow resrictor. That is what puts back pressure to the system. Without the flow restrictor the water will just flow through the unit, and with an incorrectly sized one it your membrane won't be as affective. Is it possible you upgraded to a larger membrane than what came stock with the unit?
I'd be more inclined to go with what AquaKnight suggested about the test kit possibly out of date, and they aren't 100% accurate.

 

[acrylic51]

Are you using a hand held TDS meter or are you using an inline meter to determine that you have 0 TDS leaving the unit? It's possible that your TDS is giving you a false reading and might need calibrated??

 

[no_wedge]

well the tds meter i calibrated with solution and it is good, It's a handheld, and i got a new flow restrictor with the membrane, and producing about right, at 2.5g an hour for a 75gpd.
so i'm leaning toward the test kit. I'm going to research it and see what i can find.

 

[acrylic51]

What's your water temp? I figured you had probably gotten a bigger membrane than what came with the unit. I would try to compare it with another test kit, but again the Phosphate kits are really accurate.....A Hanna Colorimeter would be the best, but you look at the price tag you could deal with what little your showing.......
On a side note I remember you saying that your using a liquid reagent? It might also be possible that you possibly added alittle more or less that could also influence the reading as well.....Just like the amonia test kits "x" amount of drops....who's to say all the drops are equal or how it was figured at the lab????