What am I doing wrong?

[scorpionsix]

Hello:

For the last week I have been attempting to follow the Pool Math app in regards to maintaining my FC; with little luck however. While the PH balance recommendations are spot on, the FC recommendations don't appear to be achieving the same results. Using the TF-100 kit, I have been testing my FC in the morning and at night each day this week. At night and after a hot day in the Phoenix desert, my FC is around 2.5. I have been following the recommendations to up my FC to 8 (my CYA is currently at 60), but in the morning on average I achieve only 4.5. My question is if I am doing something wrong when either dispersing the liquid bleach (Purchased from Walmart for $3.27 a gallon - Pool Essentials Chlorinating liquid), {or} if the summer temperatures of over 100 degrees are affecting the FC?

It is worth noting that I have not been using any Shock powder or Chlorine tabs, and have instead been relying solely on the Liquid Bleach.

In the below example, the PoolMath app is indicating to add 83oz to raise my FC to 9.
==========================================
Home - Anthem (8:24pm AZ)
------------------------------------------
Build Type: Plaster
Volume: 10000 gallons
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Latest Test Result Summary:
FC: 2.5 (24 minutes ago)
CC: 0.0 (24 minutes ago)
pH: 7.5 (24 minutes ago)
TA: 100 (24 minutes ago)
CH: 275 (24 minutes ago)
CYA: 60 (24 minutes ago)
TEMPERATURE: 90° (24 minutes ago)
CSI: -0.03 (24 minutes ago)
==========================================

In other news:
I purchased the Taylor Speed Stir and I have to say this device is AWESOME - my TA tests are now more accurate and my numbers are more consistent across the board.

 

[mknauss]

How does your water look?

You might try a true Overnight Chlorine Loss Test. You are sort of doing it, you just need to test in the evening about 30 minutes after you add the chlorine. Pump running. Then test in the morning before the sun hits the pool surface.

 

[Jimrahbe]

S,

I agree with Marty, you need to do an OCLT... If you have an FC of 8 at night and in the morning you only have an FC of 4.5, then, unless your "morning" is more like 11 am, then I suspect that you will fail the OCLT... Sounds to me like you have algae, even if you can't see it yet..

Thanks,

Jim R.

 

[Fast7]

Umm...you realize FC is being used to sanitize pool in addition to being broken down by sun? If you add recommended amount and don't test 15-30 minutes later to check if you hit your target, how do you know you didn't?

 

[IceShadow]

Another possibility if you test your FC 15-30 mins after adding and it's not where it should be is that the chlorine you're adding has degraded due to age or heat.