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Hanna Checker: Phosphate & Phosphorus

A detailed step-by-step guide for getting consistent results

  1. Bud
    Here is my step-by-step guide to using the Hanna Checker HI713 Phosphate Low Range and/or the Hanna Checker HI736 Phosphorus Ultra Low Range meters.

    I've read many complaints or comments about inconsistent readings with the Hanna meter, such as "I tested my tank water twice, back-to-back, and I got two very different results".

    I have found that following this process results in test readings that are much more consistent from test to test, as certain error factors are reduced as much as possible. You should be able to test the same sample of water repeatedly and get the same result, or at least within a few hundredths (such as test #1 = 0.03 and test #2 = 0.05). The margin of error for this test (per Hanna) is +/- 0.04, which is a pretty wide range.

    As with any test, caution needs to be taken with respect to the reagent. The reagents are not super dangerous, but could be in certain circumstances, such as if you ripped the packet open and the powder went airborne right in your face and in inhaled it. That would be bad. So don't do that. Here's some fun PDFs on the reagents:

    MSDS Sheet for Reagent 713-25
    MSDS Sheet for Reagent 736-25

    What you will need:
    Hanna Checker & Reagents (duh)
    Digital countdown timer (kitchen/grill timer, smartphone, etc)
    Optional: a small funnel with the bottom cut off

    Part 1: Prepare the packet
    1. Loosen up all the reagent by fwapping/tapping/squeezing it with your fingers while rotating the packet (move the air around)
    2. Hold the packet with one corner down and keep tapping to get all the reagent settled into one corner
    3. Cut the packet with a scissors on the 2 top edges (opposite the corner where the reagent is settled)
    4. Open the packet by grabbing the 2 side corners and wiggling it back and forth gently until it opens like a mouth. Sometimes you will have to cut a little more off the edges to get it to open up. Avoid grabbing the tip of the opening and pulling it apart - you don't want to get the reagent on your fingers and you definitely don't want to "pop" open the packet and get all the reagent in the air (see MSDS sheets above for why that is very much bad). If you have to grab the opening and get a little residue on your finger, just rinse it off and avoid freaking out.
    5. Crease one of the sides to creates a spillway for pouring out the packet, using the top edge where the 2 cut edges meet
    6. Set this aside, carefully
    Part 2: Zero / Calibrate meter to sample
    1. Fill the vial with the water sample
    2. Wipe the cuvette with a clean glasses-cleaning cloth and flick it a few times with fingertip, make sure there are no air bubbles clinging to the walls or smears on the cuvette
    3. Set your countdown timer to 3 minutes
    4. Turn on the meter, wait until it reads C1
    5. Insert the cuvette & close the top
    6. Press & release the button
    7. After the meter calibrates to the sample and displays C2, start your countdown timer.
    Part 3: Mixing in the reagent
    1. Take out cuvette and open
    2. Carefully pour in reagent, lightly tapping packet to get as much as possible in there. Try not to do this too violently as the powder is not something you want to breathe in (read the MSDS)
    3. Optionally, you can use a small funnel. Cut enough off the bottom of the funnel so that it doesn't touch the water in the vial when inserted - this will prevent reagent from getting stuck to the tip of the funnel when adding it. Insert the funnel into the mouth of the cuvette and pour the reagent into the funnel, then tap the packet as in the step above, as well as the funnel to get as much of the reagent in as possible. Be careful not to knock over the cuvette though!
    4. Place cap on cuvette
    5. With practice, this above process should take about 20-30 seconds. Make a mental note of the time left on the coundown timer.
    6. Hold cuvette horizontal and rock it back and forth. Do NOT shake vigorously. Just keep it rocking to make the big air bubble move the reagent back and forth and get it all dissolved. Keep the bubble moving. I hold the cuvette between my thumb and middle finger and use my index and ring finger to rock it back and forth, or spin it in half-turns. After about 2 minutes of this, it should all be dissolved. No matter what, if your time gets down to 25 seconds left, go immediately to the next step.
    7. Wipe the cuvette with a clean glasses-cleaning cloth and flick it a few times with fingertip, make sure there are no air bubbles clinging to the walls or smears on the cuvette
    8. Insert the cuvette & close the top
    9. Press AND HOLD button for 3 seconds until the meter reads 3:00, then release the button. The meter should start counting down.
    10. Set your countdown timer for 3 minutes and start it, so you don't forget to read the meter, as it will time-out a few minutes after the reading is taken.
    11. Once your timer goes off, check the reading.
    Step 4: Cleanup
    1. Immediately remove the cuvette and rinse it and the cap repeatedly in hot water, filling it and shaking it to get it very clean. I do this about 10-15 times, then I rinse with RO water and shake it out and set it aside to dry. This step is especially important if you have a high reading that turns the sample blue, as this will stain the cuvette (Hanna sells a solution for cleaning the cuvette due to this reason, but I've never had to use it as long as this process is followed right after the test)
    2. Throw the packet away, and again avoid doing anything that might cause a "puff" of residual reagent to go in your face or someone else's face, even if you really don't like them.
    Extra step for the HI736 Phosphorus Ultra Low Range Checker:

    This additional step removes the glass irregularity factor. The cuvettes typically do not have consistent thickness depending on the rotation, so making sure that you zero and test at the same point reduces the error brought out by this irregularity. This can also be done on the low-range checker, which may increase consistency/accuracy, but it will be to a lesser degree.
    1. Mark the mouth of the checker with a Sharpie.
    2. Mark the cuvette near the top at the bend so that you can see the mark when the cap is on.
    3. Whenever you insert the cuvette (both for the calibration and the test steps) make sure to align the checker and cuvette according to these marks.
    So that's it! Just remember, when it comes to reagents, when in doubt, don't get it in your eyes or on your skin and don't breathe it in.

Recent Updates

  1. Added funnel option instructions

Recent Reviews

  1. GoodGreef
    Ah my most hated test, the Phosphate packet dance. Tried this and it works better than the usual voodoo I practice to get the test to work.
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