Chlorine lock

[WCGG]

I live near Cincinnati and apparently have an atypical pool so the pool stores have no idea how to help me. I have a 20 year old gunite pool, Diamond Bright finish, StaRite 3 pump with cartridges and Turbo Clean caretaker system. I never had trouble balancing my water until 3 years ago. I follow the advice of the pool stores and it gets worse.
I took my water to be tested 4 days ago before doing anything. Granted, it was a pond. My test strip showed high pH, 0 free chlorine, good total alkalinity and low stabilizer.
Pool guy said throw in 12 gallons of liquid shock and a bottle of algaecide. I did. Next morning...low pH, O free chlorine, good total alkalinity, low stabilzer. Went back to pool store...was told to put in 16 more gallons of liquid shock. Next day, same readings.
Off to pool store #2...they said the chlorine was locked and that I needed to buy $165 worth of calcium hypochlorite.
Two questions:
Can I use calcium hypochlorite with a cartridge? I thought that clogged them.
Will that fix my problem?
Many thanks for anyone who knows what is going on.

 

[Mr Bruce]

Start here TFTestkits.net

Then here
Pool School - ABCs of Pool Water Chemistry

Then this one Pool School - Read This BEFORE You Post

 

[zea3]

Hi, welcome to TFP! Chlorine lock is what the pool store says when they can't figure out the problem. Calcium hypochlorite is also chlorine, it is just stabilized with calcium instead of CYA. Did they test the CYA level?

 

[WCGG]

Thanks for welcome and quick response! Yes...tested yesterday: CYA 92, pH 6.7, TA 83, FC 0

- - - Updated - - -

Thanks for the info. I have had this pool for 20 years and had no trouble balancing the chemistry until 3 years ago. I can't figure out why all of a sudden it won't hold the chlorine level and all the stores around me tell me the chlorine is locked. It makes no sense.
I was concerned being told to put in calcium hypochlorite when I have a cartridge pump and I was told not to use calcium hypochlorite as shock but to use lithium or dichlor.
If you are familiar with the equipment and balancing issues I have, I would like to hear your advice.

 

[Mr Bruce]

If those numbers are even close a drain and pH adjustment are first.

However, pool store testing is notoriously bad. You should order a recommended test kit sooner than later.

 

[duraleigh]

Welcome to the forum.

It is impossible to guess at your water's condition.

If you can post your own accurate testing, we can help you get your pool crystal clear but we are handcuffed without that information. (We will have VERY little faith in pool store results....they are bogus 70-80% of the time.)

 

[WCGG]

Draining 1/3 of my pool was what pool store 2 said...that is 10K gallons. Not an option I prefer. It's pathetic that the pool stores are so incompetent. I am still uncertain why my pool balanced just fine for 17 years and lately it's been uncooperative. Nothing has really changed.

 

[WCGG]

Store 2 uses 'fancy equipment' where they syringe water into a disc and it is put into a machine and takes 3 hours to analyze if there is a 'chlorine lock'. The equipment they use to analyze water samples is from BioGuard which has decent products but who knows. I looked at the test kits at this website but which one analyzes pH, FC, CYA, TA. What do you suggest I use to get accurate readings?
Thanks

 

[Mr Bruce]

Well there is no such thing as "chlorine lock" so I'm not sure you should worry about how fancy the equipment is

The one I linked in post #2 is the best one. I get no "kickback" from saying that, it's got the most reagents for the money and the one that has kept my pool crystal clear for 3 years.

 

[WCGG]

Oh....right. I saw the items in that test when I scrolled down this time! I didn't realize there was more to that page. Are you familiar with the cartridge pump that I have? If so, do I stay away from calcium shock? Initially, I used lithium hypochlorite as directed by the company that built my pool but I switched to Dichlor since it was similar but much less expensive. Are you familiar with the differ shocks?

 

[Mr Bruce]

Yes. All "shock" products add something besides FC. Hypo-Cal (calcium shock) adds .... calcium. Which isn't terrible until you have added so much calcium there is a problem. Dichlor adds CYA, and that never* goes away without a water replacement. And the more CYA, the more chlorine you need (see chart in signature). This is why we only sanitize our pools with chlorine, either in liquid form or via a SWG.

To determine accurately how much CYA you have, you will need a test kit that measures it. As stated, we have case after case of members comparing their test kits to a pool store's, and let's just say sometimes the pool store gets lucky.

I have a larger pool and it costs me $1.50 / day to chlorinate my pool. (If you could add your info to your signature that would be awesome, Pool size, vinyl or plaster, filter type, etc.)

*sometimes, but rarely.

 

[WCGG]

I added pool info to signature. I will get a pool testing kit and see what's going on. Thank you!