Moving to liquid bleach but can i use Calcium Hypochlorite for SLAM process?


New member
Jun 19, 2020
The Woodlands, Texas
Hi everyone! I just joined the forum after reading through all of the pool school information. The owner of my local Pinch a Penny (who is fantastic and super helpful) recommended coming here for info on switching to liquid chlorine, etc from my current process.

A little info on my pool. I'm in The Woodlands, Texas just north of Houston so it gets HOT here. The pool is regularly in the upper 80s at least during the summer. I've been using the 3" trichlor pucks and shocking using Leslie's Power Powder Plus (73% calcium hypochlorite) Usually the pool is fine most of the year but every summer I get a little algae. Nothing major but it appears on the steps and some on the walls. I always go to Leslies and they recommend all kinds of chemicals which get rid of it but it always comes back. I'm tired of fighting with it so that's why I'm here!

I've read all the recommended pool school info so I'm ready to switch to liquid bleach and stop using the pucks. However, I'm going to SLAM my pool to get rid of the algae first. Normally I would just go with the liquid bleach as recommended. However, I have a box of the bags of shock that's unopened and out of return window (purchased at the beginning of the COVID lockdown). Based on my test numbers, would it be ok to go through the SLAM process using this shock or should I just go get the bleach? I know the bleach is better but if I can avoid wasting the money already spent on the shock, that would be great. I seem to remember reading that it could affect the CH value but I think mine is on the low end anyway. Will it affect the CYA?

Finally, my CYA is obviously higher than ideal because I've been using the pucks. Should I leave it as is and assume it will lower gradually as water gets evaporated and replaced? My pool is in the direct sun almost all day and it gets so hot here so I'm constantly adding water throughout the summer.

Here are my test numbers:
pH = 7.6
FC = 5.5
CC = 0.5
TC = 6
CH = 250
TA = 70
CYA = 60

Thanks so much for the help!


Gold Supporter
Bronze Supporter
Jun 11, 2018
Verona, MO
An expert may chime in otherwise, but I would sell the shock on Craig’s list or marketplace.
If your evaporating and replacing water anyway I would live with the 60 CYA and monitor it.
Unless it is cheaper to drain a bit and refill than the extra cost of bleach for a slam. 60 vs 30 is 12ppm more.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Short answer: yes, you can use Cal-hypo. Be aware that it can cause temporary cloudiness, but if you're dealing with algae, you won't notice it much. When you get near the end, be sure you're using bleach, so that when the water is clear, you'll know it.

Plug your current numbers into poolmath, then see what happens to CSI if you double the CH. If you're still good, use some Cal-hypo since you have it. But don't buy any more. As water evaporates and you add more, CH will rise. So leave room.

If you want to know how much CH will rise, scroll to the bottom and look at Effects of Adding Chemicals. Be sure your pool's volume is correct. It will tell you how much each pound or the whole case of Cal-hypo will add.
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New member
Jun 19, 2020
The Woodlands, Texas
I added the suggested amount of the shock after your reply. It's definitely cloudy but we aren't planning to swim so it's ok for now. My FC is up to 24ppm which is where I wanted it and it raised the CH to 275 from 250. My CSI value was right round -0.32 which is a little low according to the app but the range says above -0.6 so I think I'm ok? I think I'll do one more round of the shock tomorrow am and then finish the SLAM with liquid bleach so I can make sure the water is getting clear.

Thank you so much for your help! It's very appreciated. I have been so frustrated with treating my pool and it's great to have a clear path forward vs the guessing I always got from Leslie's. The last time I brought my water to be tested, my water chemistry tested 100% according to their tests and they couldn't explain why I still had algae.
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Bronze Supporter
May 27, 2014
I've been spending time on fb pool groups and YouTube pool care channels trying to convince people that tfpc is the only major source of information using actual chemistry rather than guesses and insurance-based systems of pool care, at least as it relates to chlorine and cya management. TFPC makes our case so easy to argue. The traditional method contains no logic in its implementation. Some of you may not realize it unless you start looking around at other so-called expert advice outlets, but almost nowhere is anyone talking about the BBB or the newer-version TFPC methods of pool care; not even the most important difference; the chlorine/cya charts and management methods. Yet in all my readings of forums and comments, I've yet to find a single chemistry-based argument against the tfpc method of chlorine level management. The only argument that has ever been posed back to me is that he or she has done it this way for years or that there is more than one right way (which there is not--tfpc is the one right way); but not once has anyone said or implied that the chemistry principles scribed in tfpc methodologies is "not right" or "inferior" to any other method of chlorine management. That should tell us all something about the method of pool care that we subscribe to. Swim University is probably the best traditionalist source I've found, but they still don't use chemistry; a phrase like double shock, for instance, shows you they don't really know what they're doing. Over here, we SLAM. We know our cya level and we know our shock level; we know our daily target level and our fc minimum. Everyone else is winging it.
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Bronze Supporter
Apr 1, 2017
Houston, TX
Welcome fellow Houstonian! FYI since you’re up in the Woodlands, the BEST place to get bleach is Napco chemical on Spring Cypress near 45, kinda behind the H‑E‑B. It’s under $2/gallon for 12.5%. You can’t beat that anywhere. Get a couple 7 gallon Aqua-Tainer off Amazon - they’re way easier to lift & pour than the containers Napco will sell you. Super nice folks there too.