FAS-DPD and Speedstir -- strange results

[PoolDoc]

I'd recommend calling Taylor, and asking - 800-837-8548. If you are not getting clear answers, ask to speak

Ivusich, Wayne J.
Manager, Pool & Spa Sales
410-472-4340 Ext. 121
or
O'Grady, Jody
V.P. Sales Operations and Support
410-472-4340 Ext. 122

However, I think if you want to run this down, you're going to need to do some experimenting on your own. In fact, you'll be likely to get a more thoughtful response from Taylor (and especially, from Wayne) if you've done the process below, first.

Do this:

1. Get 2 gallons of distilled water @ Walmart (NOT spring, bottle, artesian, etc: "distilled"!)
2. Get a fresh jug of bleach.
3. Soak your test tube and your speed-stir bar overnight in 2-3 cups of distilled water + 1 cup of bleach
4. TRIPLE rinse your gear in distilled water.

5. Using your cleaned test gear, run the pool water test, side by side again.
(This eliminates stir bar or other 'carry-over' as the source of the difference.)

6. Re-immerse all gear in distilled water. Use the Speed stir in the distilled water, to clean the stir-bar

7. Empty your 1st jug of distilled water, and fill it with pool water. Take it into the house, and cover it with a towel so that it's NOT exposed to any light. Wait 24 hours.
8. Using your cleaned test gear, run the pool water test, side by side again.
(This eliminates oxidizables in your pool as the source of the difference -- the improved Speedstir mixing could result in the chlorine oxidizing goo that's already in your pool. If THIS proves to be the case, it would be a VERY interesting result, with significant implications for pool care!)

9. Re-immerse all gear in distilled water. Use the Speed stir in the distilled water, to clean the stir-bar.

10.Using your cleaned test gear, run the pool water test, side by side again. BUT, use the Speed stir to pre-mix BOTH samples before testing. WHILE testing, use the Speed stir on only ONE sample.
(This distinguishes oxidizable POOL goo, from oxidizable DPD reagent materials as the source of the difference)


11. Re-immerse all gear in distilled water. Use the Speed stir in the distilled water, to clean the stir-bar.

12. Using your cleaned test gear, run the pool water test, side by side again. BUT, add 1/2 of your FAS dose, swirl, and then wait before stirring. Let the non-Speed stir sample sit for 5 minutes, plus however long you use the Speed Stir. Let the Speed-stir sit 5 minutes before stirring.
(This checks to see if different timing due to stirring is the cause of the difference.)


(I wrote this quickly, and haven't proofed it carefully, so if something doesn't make sense -- I probably screwed up.)