Having just opened our pool, am wondering if my liquid bleach has reduced in efficacy over the winter whilst stored in our garage.

[Gasolina]

We uncovered the pool a couple of days ago. The water was clear. I tested and on Friday the readings were :
FC 3.7
PH 7.7
CYA 61
TA 99
CH 375
90,000 litres
I/G vinyl

After looking at Pool Calculator, I added 3.312 Litres of what should be 15% bleach aiming to get the FC reading of my water to 9. I was adding more water from our well So knew the reading would be lower.

The following morning (Sat) the FC read 5.8. Obviously not high enough.
I added the amount of bleach supposed to lift the water to 9. Water temp 18 degrees

I tested again that evening, (Sat) 2100 water temp 21 derees
The FC read 5.2. Again I added 2.375 L of 15% bleach

Sunday evening 1840. Water temp 21.
FC 10

This morning ( Monday )0730 water temp 18 , just as sun was beginning to hit the pool
FC 5.5. I was amazed as it would seem that I had lost so much chlorine overnight. i added 2.35l of 15%

I tested this evening (Monday) 1900 , water temp 20.
FC 4.6. Below the 5-9 range given all my readings. I added 2.75L of 15%

Mon 2100. I am really worried now. So tested again and after only two hours, the reading is only 5.8
Either we have a algae bloom or my stored chlorine is not of the right value after the winter.
perhaps both. In case the bleach is the culpri5 - even in part I must buy new in order to shock the pool.

Can anyone give me any advice as to what to do for the best?
Thank you.

 

[Bperry]

We uncovered the pool a couple of days ago. The water was clear. I tested and on Friday the readings were :
FC 3.7
PH 7.7
CYA 61
TA 99
CH 375
90,000 litres
I/G vinyl

After looking at Pool Calculator, I added 3.312 Litres of what should be 15% bleach aiming to get the FC reading of my water to 9. I was adding more water from our well So knew the reading would be lower.

The following morning (Sat) the FC read 5.8. Obviously not high enough.
I added the amount of bleach supposed to lift the water to 9. Water temp 18 degrees

I tested again that evening, (Sat) 2100 water temp 21 derees
The FC read 5.2. Again I added 2.375 L of 15% bleach

Sunday evening 1840. Water temp 21.
FC 10

This morning ( Monday )0730 water temp 18 , just as sun was beginning to hit the pool
FC 5.5. I was amazed as it would seem that I had lost so much chlorine overnight. i added 2.35l of 15%

I tested this evening (Monday) 1900 , water temp 20.
FC 4.6. Below the 5-9 range given all my readings. I added 2.75L of 15%

Mon 2100. I am really worried now. So tested again and after only two hours, the reading is only 5.8
Either we have a algae bloom or my stored chlorine is not of the right value after the winter.
perhaps both. In case the bleach is the culpri5 - even in part I must buy new in order to shock the pool.

Can anyone give me any advice as to what to do for the best?
Thank you.

Test again 30 minutes after adding chlorine to figure out if it’s weaker. It does lose potency over time.

 

[Newdude]

Breakdown of Bleach Over Time by Storage Temp - Further Reading

www.troublefreepool.com

I forever have stuff in the yard like patio furniture or the house siding that needs cleaning, that won't mind if I use weaker bleach. You can either use last year's leftovers for projects, or use more of it per dose to reach your target until it's used up.

 

[Gasolina]

Test again 30 minutes after adding chlorine to figure out if it’s weaker. It does lose potency over time.

Thanks. I thought it might be the case. Have been out and bought fresh stocks but as I am losing chlorine overnight have just started a slam anyway.

 

[Gasolina]

Breakdown of Bleach Over Time by Storage Temp - Further Reading

www.troublefreepool.com

I forever have stuff in the yard like patio furniture or the house siding that needs cleaning, that won't mind if I use weaker bleach. You can either use last year's leftovers for projects, or use more of it per dose to reach your target until it's used up.

Thanks. Interestingly was just thinking the same thing- as I have 15 litres of the weaker stuff left. Have just started a slam anyway as have lost chlorine overnight.

 

[FlappyLipps]

Using a dropper, 1 drop of 10% chlorine into 500 ml of water should test 10.0 FC
or
Mix 1ml of bleach with 100ml of distilled water, Take 1ml of that and mix into another 100ml of distilled water. Then test this mixture with your test kit like normal. Whatever ppm you get as a result is equal to the percentage in your jug.


2 1/2 years in the garage here and there is almost 0 chlorine left in the jug.