Clear, but no chlorine???

Hello! I ama fairly new pool owner (July 2012) and have a pool waiter problem that no one so far has a solution to!
Stumbled across this website while researching pool chemistry. Hoping you can help!
POOL STATS: (I tried to edit my profile but said I didn't have permission until I posted?)
15,000 SF rectangular, in-ground w/ vinyl liner
Pentair ¾ HP self-priming pump
Pentair Clean & Clear Plus Cartridge Filter. Model# CCP240.
Nature2 Mineral Sanitizer: Professional G Vessel
In-line chlorinator
Heater (gas)
Automatic Pool Cover

I keep the pool warm (80-86 this season).
I close the pool (automatic pool over) nightly, open again by 9-10am.

Chlorine Supplies: 3” tablets (GLB or Doheny’s brand):
Trichloro-s-Triazinetrione: 99%, Inert Ingredients: 1%, Available Chlorine: 90%
Superchlorinator (to shock the pool): GLB Super Charge: 68% Calcium Hypochlorite

My problem began about 4 weeks ago. I noticed that Chlorine levels (FC and TC) were steadily dropping- from 1 to .5 to zero. I normally keep FC level at 1-2 was told I didn't need to go higher since I nada mineral sanitzer and CL demand would be low.
WHen TC and FC both reached zero for several days I texted my pool guy (pool installer) and he recommend getting water tested by pool store (The Great Escape) and shocking the pool with 2 lbs shock powder.

Water testing yielded strange results: FC=0. TC=0 pH=6.5 TA=24 CYA=115, hardness =199 no metals present, HIGH phosphates present )the exact number was not given in the report).
My test rests showed FC=0 TC=.5 pH=7.2 TA=110 (I didn't have tests for other criteria)

They recommended: shock w/ 2 lbs "Natures' Way Super shock, add 22 lbs alkalinity plus, add 1 1/2 lbs pH up, add 1.5 Liters commercial strength Phos free.

I started with shock: last Friday I shocked my pool with 2 lbs Lithium based shock (they said it was the most popular type and wouldn't stain my vinyl liner. Zero chlorine reading the next morning.
Saturday evening I tried chlorine based "super shock". Zero Chlorine reading the next morning.
I didn't believe their pH and TA reading were correct so I added only phos-free on Sunday. Within an hour the filter pressure soared from 15 to 28 and water circulation slowed dramatically, and the water clouded. The next morning I barely had enough suction to vacuum up the white residue on the bottom of the pool. The pool water was once again crystal clear.

I remember my pool guy telling me that sometimes fertilizer could mess up pool chemistry and incidentally I had my lawn treated at the same time my FC levels started dropping. He suggested the pool might be over chlorinated and bleaching the free chlorine results and suggested I shock the pool again, test again for phosphates. He's not sure why shocking the pool is not raising my FC level. ARGH!!!

It's now Wednesday evening and even with reduced water flow, gunked up filters and zero FC in the water for several weeks now, the pool looks great.

Well, I am still waiting for my new filter cartridges to come in- i want my pool guy to install them only so that I can learn how to do them myself next time. (I'll admit the warning in the filter manual intimidates me…"These instructions MUST BE FOLLOWED EXACTLY to prevent the lid from blowing off during system restart or later operations"…)
Here's the latest water testing results that I took today:
FC=0
TC=0
TA=130
Hardness=750
pH=7.2
phosphates=500-1000 (did this test 3 times- dark blue but difficult to discern which color exactly)
CYA=way over 100 (the test vial (Taylor) only went up to 100, but the cloudy liquid measured 1 1/2 cm tall in the vial if that means anything.

Hopefully I'll have new cartridges tomorrow, BUt after reading about the CYA and Chlorine connection I think I understand that the amount of shock rehired to unlock the combined chlorine level needs to be much much much higher that the 2 1/2 + 2 lbs of shock that I added last week. SO why hasn't any pool guys or pool store guys mentioned this fact to me????
The kids are so bummed - they see a beautiful clear pool and don't understand how it can be so d dirty they can't swim in it….HELP!

Pick up a cheap OTO / pH test kit. The OTO (yellow drops) it is reliable well outside normal range and will tell you if chlorine is high or low.
Do you have a K-2006?
Dilute a pool water sample 1:1 with tap water and measure CYA of diluted sample(then multiply by 2). If it's still over 100 (200) then dilute a pool water sample 1:2 with tap water and measure CYA of diluted sample(then multiply by 3).

Good Morning. I have only ever used Taylor drop testing kits. Currently I have: K2006, K1004 (residential trouble shooter) and K1106 (phosphate). This morning I tested again: FC=0, Ph-7.2, TA=130. I ran the CYA test 3 times and took an average: 150.
My new filters have bee installed.

I suggested the OTO kit because OTO will not bleach out in high chlorine.

How did youn test CYA 150ppm?

Congrats on the new filters.

And, thank you for the subscription! :)

OK- I will try to get the OTO kit, but I did try diluting the pool water with bottled water (all I had) and testing using at different concentrations: 1:2, 1:4 1:9 and got zero chlorine reading all times. I got the CYA reading by diluting my pool water with tap water as you recommended: 1 part pool water, 2 parts tap and got around 50 so I tripled it to get 150.

The Walmart/Target stores in my area are all out of hth OTO chlorine testing kits (it's a short swim season here in Illinois). But I did read something in Taylor's manual about how to test for high levels: they suggested adding the 5 drops each of Reagent #1 and #2 into the vial and THEN adding pool water a drop at a time to see if there is any CL is present, so I tried this and the sample never turned pink.

If you can't find an OTO kit at Walmart or Target, you can get one at your pool store but just do not let them talk you into buying anything else. They will try!

Thank you Watermom!!! I think the problem is: the new post section does not show up at this time ( although it did earlier today).
Anyway- I did find some OTO from a neighbor who had 2- and tested for chlorine and got zero again. Just to see that the OTO was indeed fresh and working I added a drop,of bleach to some water and tested it and it came out dark orange. So I think we an say that my pool has zero chlorine in it, however LOTS of CYA.

Hey, Maryjo.

I am not going to make any chemical recommendations because I am new to the BBB method myself and there are MANY experts here who can help you. (I know what I would do with your test results but...... hint: it starts with b l e a and doesn't include t r i c h l )

I live in Saint Charles, IL so I know what's available in our area. If you HAVE to purchase any chemicals from a pool store, I recommend you go to In-The-Swim. Their corporate offices are in West Chicago and they have an outlet store right there. (They also carry Taylor reagents in case you need them right away). I would not suggest returning to The Great Escape. If you are in doubt, remember that they recommended Alkalinity Plus when your TA is fine.

Get some FC in that pool, and good luck!