A plan to drain for for Iron/CYA (review request)

DrGoguma

Member
Aug 27, 2024
10
Austin, Texas
Pool Size
5300
Surface
Plaster
Chlorine
Liquid Chlorine
Okay, as previously discovered in my beginner thread (First test results are a little worrisome), I have high CYA and iron stains. Please help me, a beginner, formulate a plan to resolve both issues on my 2 days off in 10 days.

First, chemistry:
FC 10ppm (today)
Ph 7.2 (today)
CYA >178 (probably closer to 250 -- but who knows, I tried it at 50% dilution and it was over 200 on my test)

Further notes, my DeltaT is 3.45 (assuming Leslie measured pool tds of 1000ppm, city specified TDS of city water at 247ppm), my pool is 5.3K gallons.

The plan: Pull up the iron, replace the water, get into maintenance. Liquid chlorine and chill thru the rainy season.

1. I plan to buy this submersible pump (submersible pump)
2. I plan to buy this abscorbic acid (ascorbic acid)
3. Measure the rate I can fill the pool (the most likely bottleneck)
4. Pull out the cartridge filter
5. Spend 24 hrs treating with abscorbic acid (0.5 lbs to begin with, add more if stains still persist at 8 hrs)
6. I plan to sequester if you say I need it (the pink stuff)
7. After 24 hrs of abscorbic acid, begin the water change
8. Perform an in-place drain with a pump at the skimmer and a hose at the deep end (3hrs, approx 6k gallons I guess, so 20% more than pool volume)
9. In the worst case I'm sitting at CYA 30ppm I guess. Best case 0ppm CYA.
10. Immediately dose with 60 oz of 10% liquid chlorine, should get me to approx 4-5ppm FC.
11. Check chlorine daily for next 4-5 days, performing Ph fixups and chlorine fixups.
12. After 3 days, if CYA is low, dose to at least 30ppm and set FC at maintenance.
13. On the following weekend, perform overnight chlorine test to confirm that I am in decent maintenance.
14. Have a margarita.

Okay, what steps am I missing or over simplifying?
 
Last edited:
You might review the following:


Your limitation will be fill rate, likely 5-6 gallons per minute (14-18 hours). You will need to either turn pump on/off to match input, or add head (raise the output hose over a tall ladder) to match input.
Interesting point, I'll measure fill rate this week, and get a weaker pump I suppose. Given the length of hose I need to dump the water in an approved location, I'm not sure I'll have much additional slack for a ladder.
 
Reading the rules for dumping water locally, it appears that if chlorine is less than 0.1mg/L I can dump the water in the storm drain. Which would be nice. Since I'm treating with ascorbic acid, it would seem I'm going to be pretty close to that already. I looked at pool calculator, but did not see a way to see how 8oz of ascorbic acid would effect FC.

Trying to think about how to schedule this, my goal was to be at approximately 8ppm of FC on Thursday morning, at which point I would add the ascorbic acid and try to get the iron stains up. If this google AI statement is correct:

Ascorbic acid, also known as vitamin C, neutralizes chlorine in water at a rate of 1 gram of ascorbic acid per 100 gallons of water for every 1 milligram per liter of chlorine. This reaction is very fast.

Then approximately 425g of ascorbic acid would get the 5300 gallon pool chlorine to 0 -- maybe within 30mins to an hour? At which point, I could add another half pound (approx 250g) give the pool a few hours in this state to lift the iron spots, and then start dumping the water the following morning (I'm loathe to dump water overnight when I can't monitor it -- and algae shouldn't really be a huge problem over night anyway I guess). Presuming the acidity doesn't rot out my pool pump, maybe compressing the timeline is the better bet.
 
You are correct on the AA eliminating chlorine.

Do NOT use your pool pump when AA is in the water. Use a sub pump, trash pump, etc to drain the pool.
 
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