Newbie...help!

[skyfly27]

Hi everyone. I am a new pool owner. We have a gunite 18,000 gallon in-ground chlorine pool that is several years old. Sand filter. Trying to figure out this testing part. Here are my numbers...I am not sure where to start. The water looks clear, but some of my numbers are off.
pH 7.7
FC 2
CC 0.5
total alkalinity 140
calcium hardness 200
CYA 100
My understanding is that the CYA prevents the chlorine from being burned off by the sun. But will a CYA level that high, I would have to maintain my chlorine at a much higher level in order to prevent algae from growing. It is also my understanding that the only way to lower the CYA level is to drain some water and refill. How much water do I need to drain? Also, I need to fix my pH level. In looking at the Taylor booklet that came with my kit, I would need to add 430 ml of muriatic acid. Should I get the CYA fixed first before I start treating the pH? We were hoping to heat the pool and swim this weekend. Is this ok to swim in right now? We are in Missouri. Thank you!

 

[mknauss]

Welcome to the forum!
With a CYA of 100, I suggest you follow Step 8 in CYA - Cyanuric Acid Test - Trouble Free Pool
That will tell you if your CYA is over 100.

Your pH is fine. Your FC is very low. You will most likely need to exchange a large portion of your pool water to fresh.
If you wish to swim this weekend, once you get your final CYA test results, add enough liquid chlorine to raise your FC to 10% of your CYA level. Do not test pH if FC is above 10 ppm as that test will be invalid.
I suggest you read ABC's of Pool Water Chemistry.

 

[skyfly27]

Welcome to the forum!
With a CYA of 100, I suggest you follow Step 8 in CYA - Cyanuric Acid Test - Trouble Free Pool
That will tell you if your CYA is over 100.

Your pH is fine. Your FC is very low. You will most likely need to exchange a large portion of your pool water to fresh.
If you wish to swim this weekend, once you get your final CYA test results, add enough liquid chlorine to raise your FC to 10% of your CYA level. Do not test pH if FC is above 10 ppm as that test will be invalid.
I suggest you read ABC's of Pool Water Chemistry.

Thank you very much. How much should I drain to start?

 

[Teald024]

Hello and Welcome to TFP!!

It is a simple ratio. If you want to get CYA from 100 to 50, then you need to drain 50% of the water and refill.
You need to pay attention to the ground water level so that you don’t drain too much water. Do you have a well point near the pool?

 

[skyfly27]

Hello and Welcome to TFP!!

It is a simple ratio. If you want to get CYA from 100 to 50, then you need to drain 50% of the water and refill.
You need to pay attention to the ground water level so that you don’t drain too much water. Do you have a well point near the pool?

Yes we are on well water. I would have to drain the water down the hill. The well is also down the hill but to the right.

 

[Teald024]

Based on this reply, you shouldn’t have to worry about draining the pool.

 

[skyfly27]

Based on this reply, you shouldn’t have to worry about draining the pool.

Isn’t draining the pool the only way to lower the cya level? I’m sorry, I’m so new to this

 

[mknauss]

Isn’t draining the pool the only way to lower the cya level? I’m sorry, I’m so new to this

Correct. Have you done the dilute CYA test?

 

[skyfly27]

Correct. Have you done the dilute CYA test?

Yes. I got a result of 90

 

[mknauss]

At a CYA of 90, if your pool will pass the Overnight Chlorine Loss Test, you can make a decision on draining some water or not. You can maintain the elevated FC needed for that CYA, with only checking pH when the FC is at 10 ppm or less.

Do you have iron in your well water? That may present a different challenge if you plan to drain and refill. Also understand that draining a pool entails risk.

Draining - Further Reading

www.troublefreepool.com

 

[skyfly27]

At a CYA of 90, if your pool will pass the Overnight Chlorine Loss Test, you can make a decision on draining some water or not. You can maintain the elevated FC needed for that CYA, with only checking pH when the FC is at 10 ppm or less.

Do you have iron in your well water? That may present a different challenge if you plan to drain and refill. Also understand that draining a pool entails risk.

Draining - Further Reading

www.troublefreepool.com

Yes we have iron and very hard water. The only reason I know that is our water softener inside isn’t working well. I had spoken with a plumber about adding an iron shield.

 

[mknauss]

As you get rain, I would suggest you look for ways to capture as much rain water as possible and direct it to the pool. Drain off a few inches of pool water before a big rain. Lower your CYA that way. Try to minimize however you can the amount of well water added to the pool.

 

[skyfly27]

As you get rain, I would suggest you look for ways to capture as much rain water as possible and direct it to the pool. Drain off a few inches of pool water before a big rain. Lower your CYA that way. Try to minimize however you can the amount of well water added to the pool.

Ok will do. Thank you so much for all of your help!