# Thread: Am I doing the math right?

1. ## Am I doing the math right?

Okay, got a 10 day trip coming up next month.

Chlorine consumption is about 2 ppm/day. So.... I'll need to add 20 ppm. Are you following? CYA is about 40, so I want to add some more. Some part of the pool is in the sun from about half an hour after sunrise until about half an hour before sunset. 50 or even 60 wouldn't be excessive, IMHO.

Trichlor tablets seem like the way to go. If I add 20 ppm via pucks, I will add 12 ppm CYA, correct? And to add 20 ppm to a 16000 gallon pool will take about three pounds of trichlor. I've seen individually wrapped pucks for sale on the counter at the local pool store. Should I just go buy three pounds worth?

Someone please check the math and tell me, am I right?

2. ## Re: Am I doing the math right?

I dont even like to mess with the pucks since we know they add CYA. Why not just boost your FC based off of your normal loss with bleach and maybe bump it up 5-6 ppm more. That is what I have done when I leave and my pool is in full sun from sun up to about 5 pm. So direct sun for about 8-10 hours. I have done it three times, twice in the summer heat in texas and came back to no issues.

3. ## Re: Am I doing the math right?

You are losing about 2 ppm out of what, say 5 ppm FC as your target? So let's say this is 40% FC loss per day. After 10 days this would result in only 0.6% of your original FC level and that doesn't count some absolute losses that will use up chlorine even faster. I don't think you could just shock the pool and go much more than a week at your loss rate. Even if your loss rate were 30% per day, after 10 days you'd have only 3% of your original FC level so starting even with 20 ppm FC would end up with 0.6 ppm if you were lucky.

The Trichlor pucks should work, but you'd need to dial down the feeder appropriately and if all the pucks are sitting in water, then the chlorine supply rate wil be higher initially and lower later Ideally, some Trichlor pucks will be sitting in the water and some above and as the ones below dissolve then the ones above sink lower.

4. ## Re: Am I doing the math right?

Covering the pool is a better option.

5. ## Re: Am I doing the math right?

Definitely. With a mostly opaque cover, preferably.

6. ## Re: Am I doing the math right?

Maybe not possible for you, but what I do is bring the FC up a few ppm higher than normal, then just have a neighbor add bleach daily so it stays at that slightly higher FC

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