Taking way more chlorine than usual


Gold Supporter
Bronze Supporter
May 18, 2016
We opened our pool late this year. We had lost a LOT of water. We first tried to make arrangements for a new liner, as ours is old and faded and we feared a leak. But all the companies we contacted about getting a liner said the same thing, that those orders are very back-ordered, and it could take months. So we decided to fill it up and make do - thus the even later opening, which was around 6/23/20, finally. It's holding water as well as it has in the past - just seems to need to be topped off occasionally, which we attribute to evaporation. (?)
The problem is that it is taking a LOT of chlorine every day, even though all the numbers seem to be right. What am I overlooking?
We first brought up the CYA and got pH and TA in check. We SLAMed until we passed the OCLT. Here are our current numbers:
pH 7.5
TA 70
CH 0
CYA 40

We continue to pass the OCLT, as I check it frequently, thinking there must be some hidden algae. We have been brushing frequently. But the pool is crystal clear - it sparkles. So why is it taking 2 and sometimes 3 gallons of bleach per day? This time last year, it was almost consistently 61 oz, with the very occasional 72 oz, 81 oz, or 102 oz.
We have a 20,000 gal inground with sand filter. The cost of bleach is going to drain us at this pace.

Oh...and a separate question: When we first bought this house with this pool that we knew nothing about a few years ago, I purchased a product called Jack's Magic The Filter Fiber Stuff - but we have never used it. Is it any good or should I throw it away?

We appreciate any help you can offer regarding our bleach gobbling pool.
Thank you!


Well-known member
Jun 19, 2020
What is your CC?

The fiber stuff is cellulose. It can be added to a sand filter similarly to how DE can, to filter finer particles. I've been using it to help clear a swamp. If you use it, keep a close eye on pressure. The pressure won't do anything for a while and then rises quite quickly. For me (swamp), pressure remains at start for about ten minutes and then starts going up about 1 psi per minute.
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Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
1 gallon of 10% should raise FC by 5 in your 20,000 gallon pool.

Test your FC 15 minutes after adding liquid chlorine and see what FC rise you are getting.

I looked at your PoolMath logs and they show very low FC levels. You need to log all of your tests and chlorine additions as you do them for us to see what is happening.


Gold Supporter
Silver Supporter
Jul 8, 2013
Columbus, Ohio
Check it again in the next hour or so and see if the level holds. You might check it several times during a day and see if it holds and/or how fast it drops. A big drop in a short period of time means you have something going on. A little drop from all day in the sun is normal. Post what you see and we can go from there.


Gold Supporter
Bronze Supporter
May 18, 2016
Since your request, I've only remembered once to check the FC shortly after adding chlorine. Sorry, dang it! I will set reminders in my phone to check it a few times throughout the day today. Even so, it seems to be only requiring 1 gal per day over the last couple of days, which is encouraging. Buuuuut...I checked the other levels and our pH is high 8.0 (at least). We added muriatic acid yesterday morning and it still reads 7.9, so we'll add a bit more today. TA is up to 80. CYA reads 35ish, but that test is the most subjective one - my readings seem to vary with the sunlight, so I feel like it is fine. I'll let you know how today goes. Thanks!