Can't keep chlorine levels up

ibseanb

Member
Jul 26, 2021
23
Ohio
Hi all, new here and looking for help beyond what my pool company can offer.

I have a 16,500 gallon fiberglass pool with a SWG and cartridge filter. I'm fairly sure my SWG is working since when I had it closed for a week or two at BOOST levels (forgot all about it), the levels were off the chart and I had to add Chlorine reducer to get it back to acceptable levels. The SWG is mostly grey/black with a little calcium deposit at the one end where it hooks up to the electricity.

Pool has been mostly clear since.

About a week ago, we had a family gathering where we had a pretty high bather load compared to normal. We closed the auto cover and kept the SWG at 25% where it typically stays. Upon re-opening the cover, we found a greenish cloudy water (algae bloom I suspected). Chlorine level was almost 0.

Over the next few days, I dumped several gallons of 12.5% chlorine shock, tested an hour or two later and it read > 10. TA was high, but I suspected the copious amounts of shock contributed to this. I closed the cover and ran the pump on high and SWG on boost overnight. Next day, the levels were back to 1 or so (based on test strips, Taylor 2006C is on its way). More shock was added and I tried lowering TA and PH using PH down.

I added more shock last night, and today I took a sample to the pool store and here are levels:

Pool temp: 88

FCHL: 1.5
CCHL (whatever that is): 0
PH: 7.6
Alk: 170
CYA: 30:
Calcium: 200
Salt: 5200
Phos: 100

I was advised to add 2lb of CYA and 3 more gallons of 12.5% shock (tossing CYA into the pool and no vacuum for 3 days).

Using the link on appropriate CYA - FC levels, it says I should have around 70ppm CYA. I was going to do the "sock" method in the skimmer instead of just sprinkling it in, but should I start slow with 2lb and further increase or just do 3lb out of the gate?

Should I worry about TA and PH at this phase? The water is mostly clear, just a slight (I mean very slight) haze at the deep end. It feels like adding more shock will raise TA, which will make the haze worse.

Thanks in advance.
 
Last edited:

reggiehammond

Gold Supporter
Oct 4, 2020
373
Fort Worth, Texas
Pool Size
30000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
First, get out of the pool store. Terrible, terrible advice. CYA thrown into the pool will stain. You also don't want to raise your CYA until you complete a SLAM.
Wait for your test kit - then first step of a SLAM is to lower pH to 7.2 using Muriatic Acid. Dry acid, that you've used, adds sulfates which creates problems.

Once you've completed the SLAM, you can add the stabilizer and dial in the SWCG.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,607
Texas, San Antonio/Marion, South-Central Area
Pool Size
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Surface
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Chlorine
Salt Water Generator
SWG Type
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^^ I agree. Wait until you get the test kit and eliminate the guesswork. You can't believe how bad store testing can be. We'll watch for your numbers.

Welcome to TFP! :wave:

 

ibseanb

Member
Jul 26, 2021
23
Ohio
Thanks for the quick responses. Do you think there is some algae still eating the FC in the pool? It has been covered most of the time, so UV should not be a factor in lost FC.
 

reggiehammond

Gold Supporter
Oct 4, 2020
373
Fort Worth, Texas
Pool Size
30000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
Thanks for the quick responses. Do you think there is some algae still eating the FC in the pool? It has been covered most of the time, so UV should not be a factor in lost FC.
At the FC levels you reported, almost certainly. I'd go to SLAM no matter what...
 

ibseanb

Member
Jul 26, 2021
23
Ohio
Ok. Test kit came in, and I tested the chlorine a few times, other readings once:
FC: 4.8
CC: (one reading was .4 and the other was .8)
PH: 7
Alk: 200
Calcium: 90:
CYA:30

The CC concerned me. Having friends over to the pool tomorrow, so I dumped a gallon of 12.5% shock in and running on high. Will do more readings in a few hours. I put a gallon in last night and just tested at 7pm (auto cover was closed the whole time).

Monday is supposed to start cooling down, so I was hoping to limp along until then to do the SLAM.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,607
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
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Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
For the OCLT, be sure to leave the SWG off about 45 min before grabbing the nighttime (first) water sample. Then test again in the morning before the sun hot the water.
 

ibseanb

Member
Jul 26, 2021
23
Ohio
I didn't see your response in time. I left the SWG on all day/all night. I dumped in more 12.5 and read a FC of 12 and a CC of 1 yesterday evening. Cover was on all night, and around 11am I opened the cover and took another reading. FC 8.4, CC .4. A smaller drop in FC overnight.

I'm not sure how long after my addition of the gallon of shock I should wait. I think I waited a couple of hours, pump running. Should I leave the cover off for a while?

With the current CYA of 30 (last I checked), is it safe to swim?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,607
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
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Chlorine
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SWG Type
CircuPool RJ-45 Plus
A CYA of 30 is safe to swim and as long as the FC isn't over 12 (SLAM level). Yes, I would leave the cover off a few hours each day so the sun can help to process waste and help wit the oxidation process.
 

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ibseanb

Member
Jul 26, 2021
23
Ohio
Hey all, thanks for all the help so far.

Its been about 6 days since I added any shock, and slowly but surely my FC is creeping up with my SWG on 100%. Most of the other readings are about the same:

FC 4.4
CC .4
PH 7.4
ALK 200
CYA 30
CH 90

The water is clear, but a slight haze at the deep end, guessing the Alk is to blame here. I think I finally killed whatever was eating my FC, and don't tell my wife this since she suggested it several days ago, but keeping the cover off for a day or so seemed to be the tipping point. We didn't have a cover all last year, and just had one installed right about the time all this good time started.

Suggestions on what needs adjusted? Bring down ALK then boost PH? When should I add the CYA? Once the FC is at 7?

Thanks again,
Sean
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,607
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
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The TA wouldn't be my #1 concern right now. Since you had algae issues before, I would ensure that all 3 SLAM criteria have passed first. With a CYA of 30, an FC of 12 was required until passing all 3 criteria. Maintaining the elevated FC level is best done with liquid chlorine since SWGs are not designed to produce that much chlorine. So I would leave everything alone except for the FC, get it to 12 with liquid chlorine, maintain it, and complete the SLAM Process. Passing the Overnight Chlorine Loss Test is the final step of the SLAM, then you can adjust the other items. If you elect to stop the SLAM Process early, the algae can come right back.
 
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