My tank generally tests on the Hanna PO4 Photometer to be around 0.02-0.04 range. I also test my RowaPhos reactor to know when to change it out.
My latest test on the tank and reactor came to 0.04 leading me to think it is time to change the RowaPhos. I then tested my saltwater mixing and also got 0.04. Strange. I then went to the RO/DI reservoir and got 0.04. Thinking there must be something that needs to be replaced on my RO/DI unit (SpectraPure MaxCap 100 UHE) I decided to test some distilled water just to be sure the PO4 readings are accurate.
The Distilled water (CVS brand) produced a reading of 0.02. I then retested my RO/DI and got 0.03. I then retested the distilled and got 0.03. I decided to try for a 3rd reading on the distilled and ended up wih 0.04.
To summarize:
Tank Results: 0.04
Saltwater Mix: 0.04
RO/DI: 0.04 / 0.03
Distilled: 0.02 / 0.03 / 0.04
I realize that the photometer has an accuracy of +/-0.04 and this is all within range. I guess I just expected it to be more precise than it is.
Bottom line, a reading on my tank of 0.04 is the same reading i got on the 3rd test of the distilled water leading me to believe that 0.04 may be as good as 0.00 and only readings above 0.05 would deffinitively indicate the presence of P04.
I am just curious if others using this device found similar results.
FYI:
1) I aways hold the glass with a paper towel to avoid fingerprints and wipe the outside before readings.
2) I rinse the glass using the sample to be tested prior to each test.
3) I "zero" the unit with each sample before adding the reagent.
4) I add reagent, insert plastic stopper and screw on cover
5) I then press the "Read Timed" button and swirl/shake the sample till the timer is down to 1:00.
6) Lastly I insert the sample into the unit and let the sample settle for the last minute till the reading. (the reagent does not completely dissolve).
My latest test on the tank and reactor came to 0.04 leading me to think it is time to change the RowaPhos. I then tested my saltwater mixing and also got 0.04. Strange. I then went to the RO/DI reservoir and got 0.04. Thinking there must be something that needs to be replaced on my RO/DI unit (SpectraPure MaxCap 100 UHE) I decided to test some distilled water just to be sure the PO4 readings are accurate.
The Distilled water (CVS brand) produced a reading of 0.02. I then retested my RO/DI and got 0.03. I then retested the distilled and got 0.03. I decided to try for a 3rd reading on the distilled and ended up wih 0.04.
To summarize:
Tank Results: 0.04
Saltwater Mix: 0.04
RO/DI: 0.04 / 0.03
Distilled: 0.02 / 0.03 / 0.04
I realize that the photometer has an accuracy of +/-0.04 and this is all within range. I guess I just expected it to be more precise than it is.
Bottom line, a reading on my tank of 0.04 is the same reading i got on the 3rd test of the distilled water leading me to believe that 0.04 may be as good as 0.00 and only readings above 0.05 would deffinitively indicate the presence of P04.
I am just curious if others using this device found similar results.
FYI:
1) I aways hold the glass with a paper towel to avoid fingerprints and wipe the outside before readings.
2) I rinse the glass using the sample to be tested prior to each test.
3) I "zero" the unit with each sample before adding the reagent.
4) I add reagent, insert plastic stopper and screw on cover
5) I then press the "Read Timed" button and swirl/shake the sample till the timer is down to 1:00.
6) Lastly I insert the sample into the unit and let the sample settle for the last minute till the reading. (the reagent does not completely dissolve).
