Inherited a pond, trying to turn it into a pool!

[Yeggim]

Ok, a 6ppm increase with 12.5% bleach equates to around a 21,000 gallon pool. Pretty good logic you got there. Can you post measurements? I'm sure someone on here can figure it out.

Chlorine loss is more of a percentage function. The higher it is the more you lose. You seem to be at a 30% loss more or less. That ain't bad. I see no harm in bumping CYA up 10ppm. Let's get a solid number for pool volume first.

[CarlD]

Yes, you've used the Rule of Thumb in reverse, and done so correctly. It's not that accurate--you are still fighting bio mass, and an elevated CC. You also don't know if the 12.5% is actually that (you can test it, easily enough) So a gallon of 12.5% raising it 6ppm doesn't guarantee your pool is 21k. It could be as low as 18k or as high as 22K. But the good news is: It doesn't really matter. Just assume 20,000 gallons and figure accordingly. You'll be fine.

To test your LC's strength: you'll need a 10ml measure--Drug stores sell glass eyedroppers marked to 10 ml. Fill a 5 gallon bucket with 10 liters of tap water....that's 5 x 2-liter soda bottles. Test the tap water for FC and CC...if it's city water you'll want to know how much is there and subtract it. Now add 10ml of your 12.5% to the 10 liters and mix. Test it with your FAS-DPD test. Whatever the test shows, minus the chlorine that was in the tap water, is the actual strength of your LC. Mine usually tests at 14ppm, but it may well be as low as 10ppm.

Again, 20,000 gallons is good enough for your reckoning.

Carl

[barma16]

Thanks - +/-20k tallies with my rough calculations based on measurements too, so I'll stick with that as a working number. Pool is now clear of all leaves, and the water looks crystal clear to me, but I'm still losing 2ppm overnight. Last night I was at 16ppm, and this morning I was at 14, so 12.5% loss. The night before was approximately the same (I don't have my numbers in front of me). The filter still needs backwashing every day or two, so there's clearly still something in there that's not visible to the naked eye.

Given that I'm still backwashing fairly regularly, and therefore replenishing water from time to time, would it make sense to leave the CYA until the filter runs for rather longer, instead of diluting it when I top the water up?

At 12.5% overnight loss in an unstabilized pool, can I start letting the level drift down yet?

Thanks as always...!

[BigDave]

If I were in your situation, I'd maintain shock level until you measure less than 1ppm drop over night plus one more day for good measure. After that , I'd let it drift down. After the FC is down to normal - high normal, I'd add half the calculated amount of CYA and retest CYA in 5 days and 7 days. If both readings are the same, add more if needed - wait and test - CYA disolves very slowly and overshooting the goal makes new problems. Maintain FC level using bleach or liquid chlorine.

[Yeggim]

Given that I'm still backwashing fairly regularly, and therefore replenishing water from time to time, would it make sense to leave the CYA until the filter runs for rather longer, instead of diluting it when I top the water up?

Sounds like a plan.

At 12.5% overnight loss in an unstabilized pool, can I start letting the level drift down yet?

Thanks as always...!

Sometimes the testing times will influence that overnight loss number. With low CYA, testing a little too late after sunrise or a little too early before sundown might account for that extra 1ppm. What's your CC numbers?

[barma16]

Sometimes the testing times will influence that overnight loss number. With low CYA, testing a little too late after sunrise or a little too early before sundown might account for that extra 1ppm. What's your CC numbers?

Interesting you should say that - I was worried about going too far the other way. I'm testing at 10pm, so the sun is well down, and 6am (which, frankly, is a pain) so that the sun hasn't been up too long. Up at 6 again tomorrow - will post CC numbers then...

[Watermom]

As long as you test within two hours of sunrise, it is fine.

[barma16]

Apparently no change overnight. 13.5ppm last night, 13.5ppm this morning. 1ppm CC. This seems a little too good to be true, but I tested twice this morning and got the same result. I'm working on a 10ml sample though, so perhaps there's less than 0.5ppm lost... Either that, or my testing is suspect again

I guess we'll have to see what happens tonight...

[Watermom]

Good news on the chlorine levels overnight! Since you still have CC of 1, keep it at shock level again today. Just use the 10ml sample. No reason to waste the reagents and 0.5ppm accuracy is close enough.

[Yeggim]

Excellent news except for that CC reading. I'd give the entire pool a good brushing, especially the corners and the walls. Afterwards I'd jack that baby up to 20ppm Chlorine. It could be the knockout punch of this epic battle.

I think you're way ahead on the scorecard but I don't trust that judge from Algaeria. You've really done an outstanding job thus far.