Should I switch from liquid Chlorine to Tablets...Seems more economical


May 24, 2017
Hi I have been taking care of my pool now for ~2 months. After doing the SLAM process since my pool guy screwed up things have been well. I use 1 gallon of 10% chlorine every 4 days. so I use ~8 bottles per month and at $4 a pop its about $32 per month on chlorine.

I know the tablets add stabilizer, right now my CYA is at 70. if I do a half drain of my pool (maybe it will cost ~$100-150 in water) to refill it. The tablets cost ~$70 for 35lbs at my lowes. I think one tablet lasts ~1 week in my pool so this will last me for 1 yr. This would mean i spend only $70/yr on chlorine tablets vs. $360 on liquid chlorine. Its much easier and I can drain the pool once the CYA builds up again.

Any problems in my reasoning? Also how much does one 3" tablet increase CYA by? Thanks for the help.
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Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Each tablet would supply 2.6 ppm FC and add 1.6 CYA to your pool. Based on your liquid chlorine use you need about 8 ppm of FC (that is low) per week in your pool. So you would need about 3 1/2 tablets per week. That would add about 6 ppm CYA per week.

Based on your statement, you would need to drain half your pool about every 6 weeks.

There are the numbers.

Good luck.


Well-known member
Jul 10, 2012
Herndon, VA
use the pool calculator:

One 8oz trichlor tablet raises FC 2.6 in a 21000 gallon pool.

128 oz (1 gallon) of 10% bleach adds 4.8 FC.

Average FC loss per day ideally is 1 - 2. With a CYA of 70, you want to always maintain at least FC of 5 PPM minimum, with a target of 8 - 10 ( Pool School - Chlorine / CYA Chart ).

When doing manual applications of liquid bleach, it's better to dose daily, not every four days, if that's what you're doing.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
You'll soon tire of draining water just as you've tired of adding bleach. And if they slap water restrictions on again, then what?

In the winter, FC loss drops to next-to-nothing. What you add daily will likely be more like what you'll need weekly from December through April or so. So that will affect your cost calculations.

Second, as the CYA rises, the minimum FC you need to maintain also rises. How will you raise that? More pucks, which will raise CYA even more? That's going to affect the calculations, too.

So let's see... a gallon every 4 days means a quart a day means 1.75 gallons per week. If 12.5% that adds 10 FC to your pool. That's pretty low consumption, actually. To add 10 FC via pucks would take 31 ounces of trichlor. Assuming you could precisely control the rate it dissolves, that would also add 6.1 CYA per week.

You start at 70 CYA. After one week you're at 76. After two, 82 CYA. That will show up on a test as 80. So to get the CYA back down, you need to replace 1/8 of the pool water every two weeks. Or raise the FC level by adding more pucks, which raises the CYA even faster.

Do you really want to have to rebalance everything every two weeks?

It's all a long way of saying, "no" to your subject line.


Well-known member
Apr 25, 2017
Greensboro, NC
1 gallon of 10% every 4 days? That's pretty nice, I use about a half-gallon per day for a pool roughly the size of yours (it gets full sun almost all day until late afternoon).

Wal-Mart has 10% "Pool Chlorinating Liquid" for $3.64/gallon.
They also have their house brand ("Great Vaule") 8.25% concentrated bleach for $2.67/jug (each jug is 121oz so 7oz shy of a gallon).

Their house brand is 25.2-cents/oz of chlorine, the Pool Chlorinating Liquid is 28.4-cents/oz of chlorine. The house brand also tends to be much fresher, usually made within the past few days.


Well-known member
Mar 23, 2017
Katy, TX
I started off the same way you are thinking of switching now.

My pool guy gave me a bucket of pucks when the pool was built...used those in my in-line chlorinator and thought it was the coolest thing ever.....until the summer hit.

Chlorine burns off way too fast and the stabilizer goes through the roof.

You're better off just maintaining with Liquid Chlorine daily and only using a puck or two when you need to add stabilizer. Draining/filling seems like it would be a headache.
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