New pool owner - Chlorine saga

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kaminski54

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Jul 25, 2017
51
Chattanooga, TN
Hello All,

Just bought a house with a underground 25,000 gallon vinyl lined rectangular pool - about 15 years old. Originally was on chlorine with Tri-chlor, Sand filter, pump is single speed 1 HP and runs 24/7.

Typical readings were all within normal limits except FC and TC. A "good" reading would be FC 1.8, TC 3.4. A typical reading was FC 0.4 (or 0), TC 8.2. Tried shocking with Cal Hypo multiple times... used 25lbs several times. Had no luck and decided it might be the filter and sand. Also had pump problems, so decided since we needed to replace pump and filter, might as well covert to a SWCG and did.

So, pump was off for about 2 hours when converting and replacing equipment. SWCG is a Astral VX11 designed for up to 40k gallon pools. SWCG set at 6 out of 8 bars once salt level was ~4500. About 6 hours later, my wife texts me asking if our pool should be turning green. I returned home, and sure enough the pool was green but clear (you could see the bottom). No clumps, etc. Took in a water sample the next morning, and again got the typical FC and TC levels (FC 1) and had them test for copper and iron. Both negative. Was told to brush pool, use Baquacel Algeadefense (8 packs), and turn SWCG up to max 8 of 8. I did and the pool slowly cleared over about 3 days.

Repeated tests showed WNL levels for all except FC and TC. After a week of the SWCG running at max, I got another test with FC 0.4 TC 6.8. I decided to SLAM after that. Last night I added 18 121 oz. bottles of 6% Chlorox. Pool looked clear this morning. Took in a sample and got all levels WNL except FC 0.8 TC 1.4! Almost 2200 oz. of Chlorox and still this! Using the calculator, the FC level should have been over 40 ppm last night. So about 12 hours with no sunlight and all the chlorine is gone? Pool store says they have never seen anything like it and don't have any other suggestions. I don't want to just keep dumping ~$80 dollars worth of Chlorox in the pool indefinitely. Getting a proper test kit in the mail today and will repeat same 18 bottles tonight and test.

Would it be a good idea to keep solar cover on during the day with this much chlorine?

Any ideas or suggestions? Thanks!
 
Welcome!!

As you will soon find out - Pool Store testing is not used by most members on this forum for feedback or guidance. It is not accurate, repeatable, or reliable.

We suggest you get a proper test kit. I have the TF100 from TFTestkits.net. Best kit for the residential pool owner there is.

You no doubt have algae that is consuming whatever chlorine, either liquid, solid, or SWCG. You also most likely have very high CYA. But, we need you to get a test kit to confirm that.

While you wait on your test kit, I would suggest reading Pool School as much as you can. Focus on SLAM. Also, turn off your SWCG and add 1 gallon of plain, unscented bleach (8.25%) to your pool each day.

Once you get your test kit, run the tests and post them here. We will be here to help you devise a plan of action.

Take care.
 
kaminski54 said:
Tested when I got home:

1ppm FC
2.4ppm CC
pH 7.2
TA 90
CYA 60

Then added 28 gallons of 6% bleach.
Tested again 1 hour later:

16ppm FC
6ppm CC

Please advise. Thanks.
Click to expand...
28 gallons? :eek: Holy cow...

The goal with a SLAM is to kill the algae faster than it reproduces. Thus the reasoning for maintaining shock level for a long period of time rather than just 'shocking it' and calling it good, and having to shock it every week.

Go read up on the SLAM process.

Assuming your CYA level is accurate at 60ppm, you should bring your FC up to at least 24ppm, as shown in this chart.

Go to PoolMath and plug in your numbers: 25,000 gallons, 1ppm FC, and you want 24ppm of FC. It should say 1,195oz of 6% bleach, which is 9.3 gallons (128oz/gallon).

Now go down to the bottom of the PoolMath page to the 'what-if' section, and put in 3,400oz of 6% bleach (roughly 28 gallons). You (hypothetically) just raised your FC by 66ppm. :eek: :eek: :eek: Wow.


ANYWAY...
Now, you need to bring your FC levels back up to shock level of 24ppm. Back to PoolMath: put 16 in the "Now" field and 24 in the "Target" field for FC and it should say that you need to add another 416oz of 6% bleach, or 3.3 gallons.

Keep testing every few hours (don't get up at 3AM though...) and adding chlorine as necessary to keep your pool at shock level. The longer you can keep it at shock level without letting it dip down, the faster your SLAM will go.

You need to KEEP YOUR POOL AT SHOCK LEVEL until 3 things happen: your CC reading is 0.5 or less, your pool is crystal clear, *and* you can pass the Overnight Chlorine Loss Test (OCLT), which means you lose 1ppm of FC or less overnight.
 
With a pool volume that big, you really should try to get some higher concentration chlorine. 6% bleach takes a bit over 9.9 jugs to get from 1 ppm to 24ppm, whereas 8.25% "concentrated" bleach (cheap Great Value works great) takes 7 jugs to raise it the same amount. If you can get some 10% Liquid Chlorine (again, the Walmart brand will do), you only need 5.7 jugs to raise it up to 24ppm from 1ppm. And if you have any stores near you that sell 12.5% liquid Chlorine, you'd need 4.6 jugs. As you can see, buying higher concentration chlorine greatly reduces the number of jugs you need, and typically costs less per ounce of actual chlorine in those jugs. Furthermore, 28 jugs of 6% bleach equals about 10 jugs of 10% liquid chlorine (which only costs around $30-$40 at Walmart).

Also, make sure you're checking the dates on any bleach or chlorine you buy. There's a "poured" date printed on each bottle (it's the "birth" date of that particular jug, not its expiration date). Look for a code that looks like 17 140 or 140 17. That corresponds to the 140th day of 2017. There's a link in my signature for a calendar showing which day of the year corresponds to which day of the month. Try to get chlorine that's no more than 3 months old for it to be the freshest and have the most amount of chlorine in it. Anything older than 3 months might have started to degrade and not be as effective.
 
Thank you so much for the responses. I've read about SLAMing and Pool school. I've been using the calculator as well. The first night (18 jugs) I calculated 16 were needed to bring FC up to about 40. I did 18 to be safe. I didn't have my test kit yet. Last night, I did 28 just to be sure and get FC WAY up and only achieved 16ppm FC.

I tested at 0800 this AM, FC 0.8, CC 1.6! This pattern for the last 2 months is showing my pool eats up chlorine like no one has ever seen. And I can't maintain a high FC no matter what. The pool smells of chloramines as well to back up my numbers.

I'm at a loss. Do I try again with some arbitrary number of 12% bleach jugs, maybe 18? Obviously, my pool doesn't follow the calculator. Do I drain and refill? Money is starting to be an issue now as well. I've spent about $1200 over the last 2 months on shocks, chlorine, etc.

Thanks so much for any advice.
 
The CYA test is done in FULL sun, mid day preferable, with the sun at your back, tube at your waist. Fill to the lines and look for the dot, is easier since if you are between you round up to next full increment of ten.

Use poolmath, its correct. Your gallonage might be off.

I looked for the product you put in the pool and only found something close to that name for ponds. Can you take picture of bag or ingredients?

Fill out your signature so that your pool details can be seen when ever someone picks up the thread. Upper right at top of page SETTINGS, under my setting on theat page is signature.
 
What are the dates on the bleach bottles and how was it stored/where did you buy it? Something is not right about a 16 FC after adding 28 gal 6% bleach. I also recommend testing FC with a 10 mL water sample where each drop of reagent represents 0.5 ppm FC. Saves reagent and not necessary to get 0.2 ppm level of detail when SLAMing.
 

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To start, I would 100% cease using anything that is under the Baquacil trade name with a Chlorine pool. For one, BQ is incompatible with Chlorine, For another, BQ specific chemicals, even if it is only pH Up/Down, clarifier, or algaecide, are typically way over priced. Also, contrary to what the name implies, Algaecide does not kill algae.

Is your pool still green or is it a tan-ish milky color? if the latter, you may have actually found yourself in the midst of a BQ to Chlorine conversion. There are a couple more steps for a conversion, but the same advice would hold, however. You need to SLAM (There is a link for the conversion process in the Baquacil section. There is also a link to my experience in my signature.).

Finally, I agree with sccm. Try sourcing higher concentrated bleach. Your FC is way too low and your CC is way too high and it's tougher and more expensive to achieve the necessary levels of FC with your size pool at that concentration (as you have experienced). Your CYA is also a bit high to do a SLAM as well, so yes a partial drain and refill wouldn't hurt. CYA does not dissipate with evaporation or breakdown like chlorine does.
 
If I'm reading that correctly, your CC is still a bit elevated, which means there is something in the water that shouldn't be, even with it being clear. Get your FC to SLAM level, maintain it and do an OCLT tonight. With any luck you'll lick the issue within a few days.
 
Your pool is looking nice and clear, good job!

Keep up with the SLAM. It's possible that you have an issue with ammonia: sometimes, bacteria in a pool that hasn't had chlorine levels maintained can eat away at the CYA and produce ammonia as a byproduct. Ammonia takes a loooooot of chlorine to oxidize.

You're making good progress, as shown by your CC levels decreasing each day.
 
I would also suggest you avoid bumping up the FC levels super high 'just in case', because very high levels of chlorine can bleach out your liner, among other issues.

The extra chlorine would be better served maintaining the FC levels right at the shock level instead of shooting it way up and over.
 

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