FC stuck between 2 and 3, even after bleach added. Any ideas?

[goober71]

Hi All,
I've had the pool for about a month, so still fairly new at this. Have been following the Pool Math calculator and it has been working well at maintaining all the levels.

Over the last few days however, the FC level is stuck between 2 and 3, whenever i test it. All other levels are correct. Here's the data from this morning:

FC: 2.5 (added 39oz of 8.25% bleach evening before last, so was expecting this to be at least 4)
TC: 2.5
pH: 7.6
TA: 90
CH: 200 (have been adding Cal Chl the last 2 evenings, since this was at 160)
CYA: 50

Any ideas on why the FC level is not rising? Pool is crystal clear, no algae or anything.

I have an in-line chlorinator that i put 3-4 tabs into per week, and then supplement it with bleach as needed.

Thanks.

G

 

[jblizzle]

You need to be adding 2-4 ppm of FC every day and with a CYA level of 50ppm, you should NEVER let the FC drop below 4ppm.

39oz would have added about 1.9ppm of FC. If that was 2 days ago, of course the FC dropped back down. You can test the FC level about an hour after the bleach addition.

OH, just saw you are using tablets too. You need to stop that now before you CYA level gets any higher. If you did not have the tablets, after adding the bleach 2 days ago, your FC level would likely have been even lower today.

Have you discovered Pool School yet? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

 

[goober71]

So, i need to add about 40-60oz of bleach daily? Wow, that seems like a lot!
And the tabs will not work either, since they continue to raise the CYA when used?

G

 

[jblizzle]

Yes, especially in hot TX.
With more intense sun, you will lose more FC. And given the climate, I don't think you typically get enough rain to dilute the building CYA from the tablets. If you choose to continue to use tablets, then be prepared to maintain the FC higher and to replace a large portion of water every year just to get the CYA back down to reasonable.

 

[JayBauman]

And given the climate, I don't think you typically get enough rain to dilute the building CYA from the tablets.

In general, this may be true. However, last month I did the calculation and determined that I could have been exclusively using tablets to sanitize my Houston pool and NOT have had any "too much CYA" problems over the 20 months since my pool has been in service.

 

[goober71]

Yes, we do get a fair bit of rain in Houston, so it may dilute the water and bring CYA down. I have an overflow drain though, so that probably drains some water right off the top before it mixes in in heavy rains.
Thanks for the input. I'll continue to monitor and add bleach as needed. Good to know that this is not unusual!

G