I thought I had the TFPC method down

[langerking]

For a year all seemed to make sense and my water was crystal clear with no signs of green. Then I saw the slightest traces of green algae and I performed a full battery of tests which is when I realized that my CYA level had gone practically to Zero.

In the past 4 months I have had to SLAM twice and looks like I have to again.

Here are my current readings

FC: 3.5 I have kept it between 3.0 and 5.00 for months, it got to 2.5 3 times in the last month.
CC: 0.0
pH: 7.6 It was as low as 7.4 due to the addition of Trichlor Pucks when my CYA dropped
TA: 50 I haven't measured TA very frequently, it was 60 the last time I measured which was about 6 weeks ago
CH: 80
CYA: ~25 I know, this is low, but doesn't the low CYA make my FC more effective?

 

[langerking]

OK, now I feel like I am being scolded. My target has been 4.0 I measure the chlorine levels about every other day, adding approximately 1 QT of liquid chlorine each day. This is based on Chem Geek's chart. I felt I was safe as long as I kept my Chlorine levels above 3.0. So I need to increase the target you think? Based on any chart, the higher your CYA the higher the target FC. But I am understanding now that you are saying I need to get my CYA up in the (30-40) range and 25ppm is just too low.

Chlorine/CYA Chart by Chemgeek

FC = Free Chlorine in parts-per-million (ppm)
CYA = Cyanuric Acid in parts-per-million (ppm)

CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd Min ...... Shock FC ..... Yel/MstrdShock
0 ................. 0.071 ........... 0.111 ................ 0.151 .................. 0.641 .............. 1.501
10 ............... 0.81 ............. 1.21 .................. 1.61 .................... 4.5 .................. 7.1
20 ............... 1.51 ............. 2.4 .................... 3.1 ..................... 8.3 ................ 12.7
30 ............... 2.2 ............... 3.5 .................... 4.6 ................... 12.2 ................ 18.2
40 ............... 2.9 ............... 4.6 .................... 6.1 ................... 16.0 ................ 23.8
50 ............... 3.7 ............... 5.7 .................... 7.5 ................... 19.8 ................ 29.42
60 ............... 4.4 ............... 6.8 .................... 9.0 ................... 23.7 ................ 34.92
70 ............... 5.1 ............... 8.0 .................. 10.5 ................... 27.52 ............... 40.52
80 ............... 5.8 ............... 9.1 .................. 12.0 ................... 31.42 ............... 46.12
90 ............... 6.6 ............. 10.2 .................. 13.5 ................... 35.22 ............... 51.72
100 ............. 7.3 ............. 11.4 .................. 14.9 ................... 39.12 ............... 57.32
120 ............. 8.7 ............. 13.6 .................. 17.9 ................... 46.72 ............... 68.42

 

[langerking]

Actually this was the chart that I was following:

http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock



CYA 30 min 2 target 4

 

[langerking]

Based on the charts I have seen here on TFP the FC range of 4-8 would be if your CYA is 50-70.

 

[poolnoob.ca]

Jeez ask a simple question get your head bit off. Maybe more constructive replies are en route

 

[jblizzle]

Yeah, I am not sure what timerguy was talking about.

Have you previously followed through the entire ShockLevelAndMAINTAIN Process until you passed the 3 criteria to stop?
Have you pulled out the lights and looked for anywhere that algae could be hiding?
Have you been brushing the pool?

I would suggest getting the CYA up to at least 30ppm and the SLAM the pool with some good brushing.

 

[langerking]

Yeah, I am not sure what timerguy was talking about.

Have you previously followed through the entire ShockLevelAndMAINTAIN Process until you passed the 3 criteria to stop?
Have you pulled out the lights and looked for anywhere that algae could be hiding?
Have you been brushing the pool?

I would suggest getting the CYA up to at least 30ppm and the SLAM the pool with some good brushing.

Probably not brushing enough. Possibly not SLAMMING quite as long as I should either, my last SLAM was about 2.5 days. The earlier one was about the same. I am passing the 3 criteria so I ended them. I did pull out my lights and thoroughly brushed in every possible crevice around the pool where algae could hide. There is one place though, under the drain cover that I haven't cleaned - really don't like going there because of the pressure on my ears (my pool is 8 ft deep in the deep end).

I just added 216 oz of Chlorine to start the SLAM. I need to get some Stabilizer from the store.

 

[timerguy]

I apologize, I was using pool math instead of the charts. The recommended goals I was seeing was 4-8. They were wrong mostly because I hadn't entered the current cya. But even with the correct ??? Cya the goal is 6. What's crazy is my recommended fc for my swg pool is 4-11 in pool math. But that's looking at the goal range at the top of the page where the swg towards the bottom says simply 4. Does that mean I need to disregard the 11?

 

[jblizzle]

The goal numbers up at the top in the FC row match the "normal" Range down at the bottom. These are the levels for a non-SWG pool and are really not a "range" exactly. The lower number is the minimum and the larger number is a sort of daily target. The minimum is the most important to worry about.

The SWG number at the bottom is the minimum if you are using a SWG. You would likely want to dial in the SWG to maintain something a little above that.

 

[BuckeyeChris]

if you don't brush or have poor circulation, you might not be getting the bleach everywhere it needs to be. It'd be interesting to take a water sample where the algae was, and then a sample in similar sunlight exposure where there's no algae, and see if the bleach is off by a ppm or two.

 

[timerguy]

Thanks Jason, that's a better explanation than I've seen before. I'm still dealing with high fc from my slam a couple weeks ago. Since my water temp is decreasing, and my swg will stop generating fc in the near future, I'm just going to work with what I have set now in anticipation of it going down all on its own shortly. I have quite a few jugs of bleach left from my slam. My experience last winter before swg should mean my need for a bleach should again be fairly limited.

 

[langerking]

if you don't brush or have poor circulation, you might not be getting the bleach everywhere it needs to be. It'd be interesting to take a water sample where the algae was, and then a sample in similar sunlight exposure where there's no algae, and see if the bleach is off by a ppm or two.

That's an interesting theory. I think my circulation might be a little off. I am going to backwash and clean the filter when I get done with this slam.