Chlorine Lock - Cloudy Blue Pool - High CYA and High CH

[FL_Lender]

Here's my case:

Taylor 2006C results:

FC 1.0 (decreasing fast)
CC 1.2
pH 6.8 to 7.0
TA 150 (was 180 to 200)
CH 550 to 575
CYA > 100, with dilution technique: 100-120
Fe 0
Cu 0
Borate 15


First of all, I would like to thank all those responsible for running this website. It has been very helpful and educational.
I read all the materials on the website and finally got my Taylor 2006C kit. Above are my results.

Brief history of the pool:

Over 20 years old.
8000 gal pool
Oasis shape with plaster walls.
Hayward pump with cartridge filter and chlorine tablet feeder.
Owner has been taking care of the pool for many years with just Trichlor 3" tablets and Cal Hypo shock treatment.
Owner stop using liquid chlorine many years ago. Found it cumbersome. Owner is elderly.
Pools color last week was slighty bluish-green in color with yellow algae on walls.
There is also a white cloudy substance in the pool.
Pool has been suffering with algae rebounding constantly.
Cartridge filter gets dirty a lot with milky filtrate and needs to be cleaned weekly.
Owner has a polaris and no vacuum.
Owner shocks with Cal Hypo and then uses clarifier to remove cloudiness.
Owner repeats this process every week or 2 weeks.

I recently received all of my supplies (liquid chlorine, borax, bicarb, etc...) but after seeing the results, I realize that my CYA, CH, and TA are high. I'm assuming that I have a case of chlorine lock based on the long term use of Trichlor and need to drain or dilute the pool. It has been many years since the pool has been drained or resurfaced. I have been able to make the pool blue again by dosing the pool with some liquid chlorine but the algae aggressively returns. I have also been able to reduce the TA levels by aerating the pool. CYA and CH are my biggest problems and I don't feel like wasting my products until I refill the pool. I'm assuming this would be the next logical step?

I would like to hear some recommendations and comments. Thanks.

 

[JasonLion]

Welcome to TFP!

We don't like the phrase "cholorine lock", as it is misleading. Nothing is "locked", it just takes dramatically more chlorine to get the same effect as you would at lower CYA levels. Of course, more means a lot lot more to the point of being impractical, so the end result is about the same.

Everything will be much simpler if your replace about 50% of your water to get your CYA level down to something more reasonable. That should also improve your CH issue. You should also check the TA and CH levels of your fill water to see if you are going to have ongoing problems with calcium, or if that is simply a side effect of using too much cal-hypo.

When replacing water, keep in mind that you don't want to lower the pool level below the ground water level. Since you live in Florida, there is a possibility that you have a high ground water level. If in doubt it is best to replace a little water at a time over and over rather than risk draining to far and having the pool float out of the ground.

Once you have replaced water to get the CYA level down to something more reasonable, you should raise the PH up to around 7.2 to 7.4 and then shock the pool properly, as described in Pool School.

 

[FL_Lender]

Welcome to TFP!

We don't like the phrase "cholorine lock", as it is misleading. Nothing is "locked", it just takes dramatically more chlorine to get the same effect as you would at lower CYA levels. Of course, more means a lot lot more to the point of being impractical, so the end result is about the same.

Everything will be much simpler if your replace about 50% of your water to get your CYA level down to something more reasonable. That should also improve your CH issue. You should also check the TA and CH levels of your fill water to see if you are going to have ongoing problems with calcium, or if that is simply a side effect of using too much cal-hypo.

When replacing water, keep in mind that you don't want to lower the pool level below the ground water level. Since you live in Florida, there is a possibility that you have a high ground water level. If in doubt it is best to replace a little water at a time over and over rather than risk draining to far and having the pool float out of the ground.

Once you have replaced water to get the CYA level down to something more reasonable, you should raise the PH up to around 7.2 to 7.4 and then shock the pool properly, as described in Pool School.

I was thinking along these lines too. I'm going to replace the water slowly because I was more worried about the ground water level issue over anything else. I will also check the fill water source to see if our area is high in calcium. Thanks.

 

[FL_Lender]

I was able to remove approximately 50% of the pool water without any problems. The pool became a little cloudy but the FC was near zero at the time. I basically let it go since the water was bad and I didn't want to waste any product.

After adding some new water, here are my new values:

FC 1
CC 0.8
pH 7.4
TA 140
CH 390
CYA 100 (diluted sample 70-80)
Fe 0
Cu 0

Borate 15
Phosphates 0
Ammonia 0.25
Appearance: cloudy, dark, murky, non-blue. I can't see the bottom.

I decided to move forward with the shock. I added (4) 1.42 gal 6% and (4) 1 gal 10% Aqua Chem Liquid Chlorinizor. I threw in one bag of dichlor, an anti-scale solution, and a small amount of clarifier. I've been running the pump overnight and cleaning the filter constantly.

Shock results:

FC 35 (evening 6-7pm around sunset)
CC 4
pH >8
Appearance: The pool looks great! It's very clear and it has a really nice blue color.

The next morning, I did an overnight FC loss test and I lost 17.5ppm FC (50%). I threw in one bottle of 1.42 gal bleach to keep the FC up throughout the day and held it around 25ppm. I only lost about 7ppm from morning until evening. The weather was mixed: some rain, some sun. In the evening again, I added a couple more bottles of bleach and I'm currently holding it at 35ppm.

I'm assuming that I need to keep holding it here until I burn out the consumable and the FC loss decreases?

 

[Richard320]

With FC that high, your pH reading is, at best, highly suspect. Ignore it for now. It's real easy to fix later.

You need to keep the FC at shock level until it is clear, your CC is .5 or lower, and you lose 1 ppm FC or less overnight. The more often you can add bleach to maintain the FC, the faster it goes.

Pool School has articles on how to shock and how to turn a swamp into a pool. Read them, it will save me a lot of typing!

Here's a thread that shows an extreme case....80 gallons of bleach were needed!

 

[duraleigh]

FL lender,

You are on the right path and, following Richard's advice above, you will soon have a beautiful pool.

One note of caution as you proceed. YOu tossed a lot of things in the pool you didn't need. Chlorine is the key to a perfectly sparkling pool.....nothing else unless you know and understand why it's going in and the side effects it will do to your pool.

Stay the course with the chlorine and don't use anything else. :lol:

 

[Beamup]

Wait a minute. Do you mean to say that AFTER replacing 50% of the water, you still get a 100 CYA reading? And if you dilute half-and-half with tap water it reads 60-70? That would imply that your CYA was initially 250-300 (very high but could happen), and now is still 120-140. Which would make it still impractical to shock, as the required level would be about 50 ppm (!!!).

 

[Butterfly]

Welcome

Sounds like mustard algae:

....yellow algae on walls.....
Pool has been suffering with algae rebounding constantly.

Mustard has a different/higher shock level and add'l instructions.
See article in Pool School here: pool-school/mustard_algae

Use only bleach/liquid chlorine. The dichlor you used added more CYA, which you just finished lowering with your water drain/refill dance.

What type brush are you using? With 20 YO plaster, I suggest a wire/nylon combo.

Can you post a pic for us?

 

[FL_Lender]

As in my very first post the CYA was VERY high. Well over a 100 even with dilution technique. That is why I refilled it with some fresh water. There has been some improvement although the CYA, CH, and TA are still a little high. The pool is gorgeous though. Crystal clear and blue but the chemistry is saying something else. There are no signs of algae anymore especially after shock. The shock sanitized everything.

I brush everyday with a wire and nylon brush after bleaching.

The latest results:

My overnight FC loss for 8/11 was 10.5ppm. Yesterday's test had a loss close to 18ppm.
CC is low at 0.5ppm
Water is crystal clear and blue.
Ammonia is still at 0.25.

The problem is that something is still consuming the FC but it seems to be improving. May be if I raise the shock higher it should burn the consumer out but it's getting a little costly and time consuming.

 

[Bama Rambler]

If it read this right.

CYA 100 (diluted sample 70-80)

Your CYA is still about 150. If so, you still have a ways to go with the draining to get to a reasonable level.

Also you say you have about .25 ppm of ammonia in your pool. That will consume massive amounts of FC until it's gone.