how does cal-hypo compare to bleach

I have 25000 IG vinyl pool. I usually shock with bleach but have some cal-hypo on hand, but I don't know how much I should use? I put in 3 lbs. last night and this morning I have .5 FC. So I obviously needed to shock pretty bad! Just don't know if I put in enough? I added 3 more lbs this morning. How long after adding should I wait to test and see how much it brought it up?

My numbers this morning
FC .5
CC .5
Alk 90
PH 7.2 (it seems to be falling)
Cal 150
CYA 90

Best guess chart says shock to 20....????

You'll have to read the cal-hypo label to see how much it will increase the FC in your pool volume, should be a simple equation. I can vouch that shocking to FC of 20 is about right for CYA 90. I just had to do that w/ my pool and it worked quickly. I know bleach tends to raise pH and I would guess the cal-hypo would have the same effect. I'm sure some of the moderators could give you better info on what to do with your pH while in process. Your TA looks low to me, too. Good luck!

I just found a chart that says 2 oz. of 65% cal hypo will raise FC by 1 ppm in 10,000 gallons of water. Assuming this is correct (someone please advise if not), then your situation requires

2 oz. * (25/10) * 20 = 100 oz. = 6 1/4 lbs.

so your 3 + 3 is probably good (although 6 at once might have been better).

The lingering question I have, however - help from a moderator here, please - is it valid to translate 16 fluid ounces = 1 lb. when you're talking about powdered cal hypo? I'm presuming that most people measure using a plastic cup marked in fluid ounces, not with a scale.

I do not use cal-hypo in my pool, but, no, 16 fluid oz. cannot be equated with 1 lb.

Just a small note - if you use Cal-Hypo, you'll raise the calcium level. Probably not much of a concern for you with a vinyl pool and calcium level where it currently is. But if you have an SWG and/or heater, something to think about for the future (high calcium levels can cause scale, causing premature wear and tear).

Quote:

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Originally Posted by Watermom

I do not use cal-hypo in my pool, but, no, 16 fluid oz. cannot be equated with 1 lb.

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Then could someone please provide the conversion factor?

Here is the conversion. Just got a fresh 100# container of cal hypo and there was a big blue scoop included. 24 fluid oz --> 700 grams --> approx 1.5 pounds. Verified this with a scale too. The grams --> pounds (avdp) conversion numbers work out too. The ounce scale verified to be liquid too. So, one 16 oz cup full of the stuff is pretty close to a pound.
Al

OK. I stand corrected. That is interesting that 16 oz (volume) does equal a pound (weight) for cal-hypo. This won't be true of all substances, however.