1st time trying liquid chlorine - something fishy

[weaver]

I have had pool for 6 years - using chlorine tabs and struggling with CYA levels and algae growth. I just tried switching to liquid chlorine - and I was surprised how fast it leaves the pool. I have a 23K gal pool ... and with 0 ppm FC chlorine and total chlorine of 0(and CYA level of about 70) ... I put in 1 1/2 gal of 10.2% concentration chlorine (it was evening time). The next morning (12 hrs later) I tested (with taylor test kit) ... and had 8.5ppm chlorine. That evening - I tested again ... and the chlorine level was 0. Is this how much liquid chlorine has to go in the pool on a daily basis?

In summary - started out with:
TC = 0
FC = 0
PH 7.4
Alkalinity 100
Calcium = 230
CYA = 70

Again - in summary - in the evening - I added 1 1/2 gallons chlorine at 10.2% concentration - and tested the next morning early at 8.5 chlorine
12 hours later - I had 0 chlorine (it was mainly a sunny day).

I thought with the level of CYA (70)- that the chlorine would "stay" in the water... but apparently not. Am I missing something?

1st time on forum.
thx
weaver

 

[JoeSelf]

Sounds like there is something in the water. Read SLAM in pool school. Pool School - SLAM - Shock Level And Maintain This is a process not a one time thing.

 

[zea3]

Hi, welcome to TFP! The CYA acts as a sunscreen for the FC, but unlike the sunscreen we use it does not "wash away" over time it continues to build if you use products like dichlor and trichlor that contain CYA. If you think of CYA like layers of paint on a wooden board, you know that every layer of paint conceals more of the wood grain of the board. If you keep adding layers of paint eventually you will not see any trace of the wood grain. If you want to see the wood grain again you have to remove the layers of paint. It is the same with CYA, the only way to reduce its effects is to remove it from the pool by draining and replacing some of the water.

When CYA gets too high it is protecting the chlorine so well that it is not available to kill algae or sanitize the pool, and you have to have a higher chlorine level to compensate for the unavailable chlorine. CYA and chlorine must be kept in the correct ratio to be effective. With a CYA of 70 your FC should be 5-8ppm and should never be allowed to drop below 5ppm. We recommend that manually chlorinated pools have a CYA of 30-50ppm. 70ppm is a little high but not unmanagable, as long as you keep the FC in the recommended range. Always shoot for the high end of the range so if you skip a day of testing you are likely to stay in range. Use PoolMath to determine the dosage for your pool.


How does your water currently look? Is it crystal clear or a little cloudy? Since it consumed so much chlorine in a short time that suggests a nascent algae bloom. If your chlorine drops too low for a couple of days the pool will likely start to turn green. To be sure you can do the overnight chlorine loss test . If you do not pass the OCLT then you will need to complete the SLAM process.

Feel free to post any questions you may have. We are here to help!

 

[Azgirl71]

Welcome to TFP!

 

[bobodaclown]

Hello Weaver and welcome to the forums. You'll get great advice here. Zea has provided great advice. How are you testing your water?
Here are some recommendations: Pool School - Test Kits Compared

If I had to do it over again I'd just buy the TFTestkits TF-1002. It's a much better value.

There are different ways to get chlorine into the pool. Pool School - How to Chlorinate Your Pool

But always maintain at least the minimum for your CYA Level. Pool School - Chlorine / CYA Chart

 

[Divin Dave]

Chlorine is consumed by 2 things.
1. Sunlight and UV
2. Organics in the water.

With CYA of 70 with is good protection of the chlorine from sunlight burn, and you lost that much FC in such short amount of time, then certainly you have organics (algae) in the water which is consuming the chlorine. As mentioned above, you need to SLAM the pool to rid it of the algae. After that, mantain a correct FC level, and you will not have those problems anymore.

You may have clear water, but algae in its infant stage isnt visible in the water. Not until it multiplies and multiplies, does it become present to the extent that you can actually see it as green in the pool.

To eliminate factor of FC Consumption by the sun, to a Overnight Chlorine Loss Test, and your loss of FC overnight is what is being consumed by organics.
Test FC just after sun goes down
Test FC just before sun comes up
If you have more than 1 ppm loss, you have algae

 

[Richard320]

Welcome!

We have a clue:​

I have had pool for 6 years - using chlorine tabs and struggling with CYA levels and algae growth.

A green cloudy pool can deplete a couple gallons of bleach in an hour. Let's say you just have a few patches of growth and some spores in the water that haven't yet overwhelmed things. Your losses would still be expected.

You need to SLAM the pool to eliminate all the algae. And after that, the pool's appetite will go down. I have a 16000 gallon pool and it takes roughly a quart of 12.5% bleach per day during swim season. Not knowing how big your pool is, we can't even guess a range of chlorine usage for you once the algae is cleared. Please fill out the signature.

 

[weaver]

The water is very clear ... but I always get what appears to be a small residual amount of algae growth settling in some areas of the pool that does not have as much circulation. Anyhow - based on the help/guidance above .... I drained the pool last night at least 25% and refilled overnight. The CYA is now 50... and I will re-try the SLAM procedure with vigor. I was thinking that the total loss of chlorine was sun driven. But as the SLAM procedure and overnight loss test suggests - algae doesn't give up easily.

I guess I need to update my profile to give pool status/configuration. But - it is a 23,000 gallon pool.

- - - Updated - - -

I should also say - thanks for the quick response and help. I am determined to conquer this thing.