My pool's appetite for chlorine is insatiable

largesock

Member
Apr 26, 2017
9
Missouri
First off, let me say this is my first time maintaining a pool...I moved into this house in November, after it had already been winterized and covered.

I know from the pool store that they'd been using Baquacil, so one of the first things I did was pour approx 50 bottles of 8.3% bleach from Sam's Club into the pool over a period of a few days in April. It caused crazy green colors, lots of brown/amber goo at the bottom of the pool, two backwashes of the filter due to increased pressure, the whole nine yards. That all cleared up within a couple of days. I added a 3oz trichlor tab into the floater and took a sample to the pool store, who said everything checked out. The water has been crystal clear ever since.

In the ensuing week or so, I used Leslie's test strips daily, which never indicated any free chlorine at all. So I'd use poolmath and add about 96oz of 8.3% bleach daily to get a target FC of 5, which seemed about right. But every day the test strips would show 0 FC. Meanwhile the pool store consistently told me I had a level of 2ppm, which was good. But I decided I wanted more accurate tests, so I ordered the TF-100 test kit from TF test kits.

I found at this point that my FC was dropping to 0 very quickly after adding obscene amounts of chlorine. The amounts got more and more obscene. But CC is almost always around 0.5 or less.

At this point I'm trying to SLAM the pool, but I can barely get my FC to shock level for more than about 30 minutes at a time, even with very frequent addition of loads of chlorine. I've suspected my test kits, but the test strips, Taylor K-1000, and FAS-DPD tests all agree with one another. And I've also suspected my chlorine, but I've now bought 8.3% bleach from Sam's, 8.3% bleach from Wal-Mart, and 12.5% chlorine from Menards, and they all essentially behave the same way.

Here's my monster spreadsheet of what I've added and what my tests have shown: Pool numbers - Google Sheets

Anyone have any idea what's going on? Also, what's a safe FC level? I'm getting sick of dealing with the pool 20 times a day and would love to just throw 20 gallons of 12.5% chlorine in the &#$&ing thing at this point. Thanks.
 

benm2010

Well-known member
Mar 16, 2017
143
Fort Worth, Texas
Please give a full test report including CYA. A very low CYA can cause chlorine to be used up very fast. Another issue (that I know from experience) could be ammonia in the water. Won't know for sure until we see a full test report.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
11,316
Bedford, TX
large,

My initial thought was the same as Ben's above but then I looked at your spreadsheet and it "appears" that you have about 30 ppm of CYA..

Where did you get those numbers?? They do not look like TF-100 numbers???

But... assuming you have a CYA of 30, I suggest you do a OCLT... See this... https://www.troublefreepool.com/content/136-perform-the-overnight-fc-chlorine-loss-test-oclt

Basically you add chlorine just after sundown, wait 30 minutes and record FC level. Then you have to get your rear out of bed before sunup (sorry, just do it) and retest your FC. If you lose less than 1 ppm of FC over night, that generally means that nothing is in your pool is eating your chlorine, so any loss in the daytime is due to the sunlight. If you lose more than 1 ppm overnight it means that you have an algae outbreak that is eating your chlorine as fast as you can put it in.

And,,, an FC of 2 is way too low to be considered "good".. See this chart... https://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

Thanks for posting,

Jim R.
 

Flying Tivo

Well-known member
Jan 24, 2017
602
Monterrey, NL, Mexico
First off, let me say this is my first time maintaining a pool...I moved into this house in November, after it had already been winterized and covered.

I know from the pool store that they'd been using Baquacil,
This is your first problem, you need to address it. There must still be some Baq in the water and that is what is consuming your FC. Here is the process of converting to regular Chlorine pool. You started it, but probably have not finished it.

Felipe
 

largesock

Member
Apr 26, 2017
9
Missouri
So my latest test was:
FC: 4.5
CC: 0
pH: 7.4
TA: 160
CH: 325
CYA: 45

I don't know. I guess maybe I jumped the gun on thinking my Baqua conversion was done? The signs of conversion were so obvious at first, but then they totally cleared up. The water went from cloudy white to completely clear, and the tons of yellow goo I was finding floating in the pool and settled on the bottom completely stopped. Further, my Baqua test strips don't show any levels of sanitizer or oxidizer. I thought I passed an overnight FC loss test, but that was before I had a reliable test kit, so I was probably just mistaken.

I'm just finding it incredible how much chlorine this thing can eat. I've gone through about 75 gallons of 8.3% bleach and 34 gallons of 12.5% liquid chlorine. It's starting to lighten my wallet more than I'd like. But surely I must be close? It's a 13000 gallon pool. If my math is right, I've added about 10.5 gallons of pure chlorine to this pool so far. It's also really wearing on my patience to add chemicals 10 or more times a day, but I assume if I were only doing this twice a day it would take five times as long.

PS: Jimrahbe, I'm curious why you don't think those look like TF-100 numbers. If your concern is well-founded, maybe I'm testing wrong somehow.
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,341
NW Ohio
I know from the pool store that they'd been using Baquacil, so one of the first things I did was pour approx 50 bottles of 8.3% bleach from Sam's Club into the pool over a period of a few days in April. It caused crazy green colors, lots of brown/amber goo at the bottom of the pool, two backwashes of the filter due to increased pressure, the whole nine yards. That all cleared up within a couple of days. I added a 3oz trichlor tab into the floater and took a sample to the pool store, who said everything checked out. The water has been crystal clear ever since.
Wait, wait, wait. This is all you did to convert your pool from Baqua to chlorine? Did you change the sand in your filter?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
11,316
Bedford, TX
Large,

Sorry, I was not familiar with Baqua, so I missed that all together. I'd follow everyone's Baqua advice..

When measuring CYA you should round up so your numbers would be 20 or 30 or 40 etc.. When tested at a Pool Store they use numbers like 22 and 38 etc... so I thought they were pool store numbers..

But if you have the TF-100 then I take my statement back... :p

Jim R.
 

largesock

Member
Apr 26, 2017
9
Missouri
What does changing the sand in the filter do? I hadn't done it because it was new sand when I started the conversion process, and though I had to backwash a couple of times, the pressure went right back to where it was at the beginning.

But there is a simple way to test if the filter's eating the chlorine, right? I can just switch my multiport valve to "recirculate" and that'll bypass the filter -- if I do that for a couple of hours, and compare to a couple of hours on the "filter" setting, and check FC loss on both, that seems like it would tell me. I assume I should do that at night so temporary cloud cover doesn't distort the results. Does that seem reasonable to you more experienced pool people? Thanks.
 

borjis

LifeTime Supporter
Aug 19, 2014
2,705
Pacific NW
Concur. If Baqua was present when the sand was replaced, it will need replacing again to ensure it is all cleared out completely.
 

domct203

Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
3,959
CT
What does changing the sand in the filter do? I hadn't done it because it was new sand when I started the conversion process, and though I had to backwash a couple of times, the pressure went right back to where it was at the beginning.

But there is a simple way to test if the filter's eating the chlorine, right? I can just switch my multiport valve to "recirculate" and that'll bypass the filter -- if I do that for a couple of hours, and compare to a couple of hours on the "filter" setting, and check FC loss on both, that seems like it would tell me. I assume I should do that at night so temporary cloud cover doesn't distort the results. Does that seem reasonable to you more experienced pool people? Thanks.
There is goo still trapped in the sand, and it is consuming the chlorine.

Step 7 of 9:
"When you lose 1 ppm of chlorine, or less, overnight it is time to clean out your filter and change the media. Once the filter is cleaned up, add enough CYA to reach 30 ppm. Continue to maintain FC at 15 ppm."

Please read the conversion article posted by Flying Tivo.
 

largesock

Member
Apr 26, 2017
9
Missouri
Hmm. This really doesn't add up.

So, if the filter is consuming the chlorine, how would you ever get to the point of losing 1 ppm of chlorine or less overnight *before* you change the sand? I am not yet at that point. My FC goes down quickly overnight. So according to the conversion article, I should *not* change the sand in the filter.

This was my original reasoning for not changing the sand. Is that conversion article wrong? What am I missing?
 

largesock

Member
Apr 26, 2017
9
Missouri
So I think I just really jumped the gun on posting this thread. I'll keep a close eye on overnight loss, but my pool is not nearly as hungry as it used to be. Whatever is eating the chlorine is finite (well, obviously it would be) but it also finally seems to be losing the battle.

This is me trying to maintain SLAM levels of FC
May 2 (sunny): 14 gallons bleach (8.3%) plus 10 gallons liquid chlorine (12.5%)
May 3 (overcast): 16 gallons liquid chlorine
May 4 (sunny): 10 gallons liquid chlorine
May 5 (sunny): 3 gallons liquid chlorine so far today and it's 5pm. At this rate I may add one more gallon tonight.

This conversion process is not cheap, but I definitely trust that I'm moving to a much better system. Thanks for all the help, everyone.