Opening Pool - Can't get FC above 1

[Siamese]

Hi everyone. Yesterday, I opened up the pool that came with the home we purchased over the winter. It's a 40x20 inground with a vinyl liner and (according to the previous owner) 28,000 gallons. I took off the cover and found very dark green water with many leaves in it. I took out all of the plugs, added DE to the filter and got the pump and filter going. I vacuumed and scooped out all the leaves that I could find and actually took a dive in the deep end to make sure there weren't clumps of leaves stuck in the main drain.

I planned ahead and got the TF100 test kit over the winter so I was ready to go.

I first tested the Ph it came back at 7.4 - so far, so good. I was worried about the CYA because I saw that the previous owner used pucks. However I couldn't get a reading when I did the test. The black dot was visible with the vial completely filled. I assume it's somewhere between 0-20. FC came in at zero. I can't test the CC as the bottle of the 003 reagent went missing (I'm blaming one of the kids.)

I put some stabilizer in a sock in the skimmer and added 3 gallons of 12.5% liquid chlorine. Tested 15 minutes later and FC came back at 1 on both the OTO and the FAS-DPD tests. I thought that maybe the chlorine was old and wasn't good, so I bought and added 4 182oz bottles of 6% bleach. Tested again 15 minutes later and the FC was still at 1. I repeated this exercise all day yesterday with the same results. I ended up adding 12 bottles of 12.5% chlorine and the four bottles of bleach.

I ran the pump overnight - I woke up twice to recharge the DE. The water was a bit lighter this morning. When I got home from work this afternoon I added 6 more big bottles of bleach and 8 more gallons of 12.5% liquid chlorine. I tested almost immediately after the chlorine went in the water and got 2FC. After 10 minutes and again at 30 minutes it's down to 1. I tried different OTO kits and tried the FAS-DPD tests again - same thing. I bought the bleach from 2 different stores and the liquid chlorine from 2 different pool stores, so I can't imagine that it all was bad.

I add the chlorine in front of the return with the highest pressure. I tried taking my sample from different spots in pool at different height in the pool. I tried brushing the bottom and used my aquabot to churn up any "pools" of chlorine that settled in the deep end. Still nothing.

Please help - I've spent $150 on chlorine and still haven't gotten FC above 1.

I've heard the CYA can turn to ammonia over the winter and that might attack my chlorine immediately. Could that still be happening after 30+ gallons of bleach/chlorine?

Test Results:
FC - 1
CC (unknown, but there's some as the OTO test turns bright yellow after being left in the vial for about 5 minutes)
PH - 7.4
CYA 0-20
CH - 300
TA - 160

 

[Richard320]

Sounds like you have a good idea there. With CYA that low, you could use Dichlor shock. Less weight to carry, fewer raised eyebrows when you strip the chlorox shelf bare.

 

[Butterfly]

I believe you are right about the ammonia. When you lose CYA over the winter, there will be a substantial chlorine demand when you open the pool in the spring. It will probably take a substantial amount of shocking before you will be able to hold a FC level.

You need to replace the reagent and post up the CC #. Good for you for ordering your TF100 this winter and having it ready for use!....except for that one missing reagent!

I suggest you take your CYA only up to 30 for shocking purposes. Once you are done shocking, you can increase it. Having CYA higher now cost more $ in Chlorine because of the higher shock level.

You got a job ahead of you. Please keep us posted.

 

[Siamese]

Thanks for the affirmation, guys. I figured it was ammonia, but started second guessing myself after seeing my pool deck filled with empty gallons of bleach.

I think I've broken through the ammonia resistance. I added 12 more gallons of 10% chlorine and it seems to be holding at about 16ppm about 15 minutes out. I'll continue to check every 15 minutes for the next few hours and keep it above 12 ppm.

The missing reagent is on the way. Dave shipped it earlier today.

Hoping to see more of the pool floor when I awake tomorrow. I'll let you know how it goes. Agree on keeping CYA around 30 for now.

Thanks again!

 

[Siamese]

It's coming along. Pool color went from an electric teal to a light gray overnight. Clarity is improving. FC went from 14PPM to 12PPM - holding better than I anticipated. I'll bring a little higher before I go to work - it's supposed to be sunny today, so I know that I'll lose a lot with my CYA level so low.

 

[Butterfly]

Nice improvement

We're gonna' need a pic before too long

 

[Suziqzer]

Sounds like you had a big job ahead of you and you're tackling it well! You'll have sparkly water soon.. Keep working at it

 

[madwil]

sounds like you're almost there! now that it's holding FC, you're past the ammonia phase- now it's just finishing killing organics and filtering!

 

[chem geek]

I put some stabilizer in a sock in the skimmer and added 3 gallons of 12.5% liquid chlorine.
:
I bought and added 4 182oz bottles of 6% bleach
:
I ended up adding 12 bottles of 12.5% chlorine and the four bottles of bleach.
:
I added 6 more big bottles of bleach and 8 more gallons of 12.5% liquid chlorine.
:
I've heard the CYA can turn to ammonia over the winter and that might attack my chlorine immediately. Could that still be happening after 30+ gallons of bleach/chlorine?
:
I added 12 more gallons of 10% chlorine and it seems to be holding at about 16ppm about 15 minutes out.

So let's recap to figure out how much CYA was probably lost over the winter and converted to ammonia.

I count 20 gallons of 12.5% chlorinating liquid and 10 bottles of 6% bleach (I'm assuming "big bottles" are the 1.5-gallon jugs -- 192 ounces, not 182). In 28,000 gallons, that would be 89+33 = 122 ppm FC and then subtract the final reading of 16 ppm so 106 ppm of cumulative FC that was added. That could come from no more than 45 ppm CYA getting converted to ammonia by bacteria. You can see in this post how I had a similar experience, though with roughly half the amount of FC needed so around half the amount of converted CYA.

Congratulations on getting through this! From this point forward, I think you'll have an incentive to always keep chlorine in the pool to prevent any such bacterial conversion from occurring. It's too bad the previous owner left things in such a bad state.

 

[Siamese]

Chemgeek - your numbers sound about right. The previous owner used only pucks. I think the only reason the ammonia level wasn't higher is that there's a leak in one of the return lines somewhere and he was constantly replacing water last year, bringing down his CYA levels. He said his kids might have accidentally hit a line with the rototiller last spring.

So in addition to keeping the pool at shock level over the weekend, I'll be digging in the garden looking for the leaky pipe. Wish me luck.

 

[Richard320]

Chemgeek - your numbers sound about right. The previous owner used only pucks. I think the only reason the ammonia level wasn't higher is that there's a leak in one of the return lines somewhere and he was constantly replacing water last year, bringing down his CYA levels. He said his kids might have accidentally hit a line with the rototiller last spring.

So in addition to keeping the pool at shock level over the weekend, I'll be digging in the garden looking for the leaky pipe. Wish me luck.

If he's sure it was a return line, that ought to be easy to find. Unscrew the eyeballs on your returns and screw on some threaded caps. Then let 'er rip. Start digging where you see a geyser.

No, actually not such a good idea, you'd probably blow your filter or your pump seal. Stop watering the yard. The patch that stays green is where you start looking.