Does bleach get old?

[Andrew Montreal]

Hi all,

I know the answer is yes… liquid bleach will lose efficacy. But I am wondering if it can be this quick…

I tested my hot tub chlorine levels and I had gone down to 1 ppm. It was surprising considering that it was at around 4 ppm but the end of last night. But let’s say that that is fine.

The bigger surprise is that I just added 30ml of 10.8% liquid chlorine. That should have increased my FC count to approx 3.3 ppm. The thing is that I just retested and it’s only at 2 ppm.

I bought the chlorine only two month ago, though it was from the end of the store’s season. They had to go get it from the back of the Canadian Tire.

Any explanation?

Thanks,

Andrew

 

[Bperry]

Hi all,

I know the answer is yes… liquid bleach will lose efficacy. But I am wondering if it can be this quick…

I tested my hot tub chlorine levels and I had gone down to 1 ppm. It was surprising considering that it was at around 4 ppm but the end of last night. But let’s say that that is fine.

The bigger surprise is that I just added 30ml of 10.8% liquid chlorine. That should have increased my FC count to approx 3.3 ppm. The thing is that I just retested and it’s only at 2 ppm.

I bought the chlorine only two month ago, though it was from the end of the store’s season. They had to go get it from the back of the Canadian Tire.

Any explanation?

Thanks,

Andrew

What’s the CYA level in the tub? Chlorine has a very fast half life without stabilizer. The drop test has an error of +/- 0.5ppm as an added bit of info. Your experience doesn’t sound that far off from normal.

 

[Andrew Montreal]

What’s the CYA level in the tub? Chlorine has a very fast half life without stabilizer. The drop test has an error of +/- 0.5ppm as an added bit of info. Your experience doesn’t sound that far off from normal.

CYA level is above 30 ppm. I can’t be certain though due to the imprecision of the test, but the test now suggest that it’s above 30. According to my calculations, it should be at 32 ppm as I have added 106 grams of dichlor since refilling the spa.

when you speak of its half-life, are you suggesting that indeed the chlorine in the bottle is not as potent as the label suggest?

 

[Bperry]

CYA level is above 30 ppm. I can’t be certain though due to the imprecision of the test, but the test now suggest that it’s above 30. According to my calculations, it should be at 32 ppm as I have added 106 grams of dichlor since refilling the spa.

when you speak of its half-life, are you suggesting that indeed the chlorine in the bottle is not as potent as the label suggest?

Yes, the chlorine degrades in the bottle, the manufacturer has error tolerance in the process, and the water could have something being consumed by the chlorine as well. All of that stuff comes into play, which is why you should shoot for the high side of the target range and then if it’s a bit short of expectations it’s no big deal. In you case that’s FC= 6ppm.

 

[Andrew Montreal]

Yes, the chlorine degrades in the bottle, the manufacturer has error tolerance in the process, and the water could have something being consumed by the chlorine as well. All of that stuff comes into play, which is why you should shoot for the high side of the target range and then if it’s a bit short of expectations it’s no big deal. In you case that’s FC= 6ppm.

Good suggestion.

By the way, I just added another 30ml and guess what… again only an increase of 1 ppm. Clearly the liquid chlorine is down to 5% by now. Good to know.

 

[JamesW]

Check for CCs.

 

[Mdragger88]

There should be a date code on the bottle- it may have been old when you bought it especially if it was stored in the sun or a hot location.
Adjust your doses accordingly if it has degraded.

 

[Andrew Montreal]

Check for CCs.

CCs are below 0.5 when I check with 10ml and around 0.2 when I check with 25ml.

 

[Andrew Montreal]

There should be a date code on the bottle- it may have been old when you bought it especially if it was stored in the sun or a hot location.
Adjust your doses accordingly if it has degraded.

That’s what I’ve been doing… 60ml instead of 30ml.

Though question… the chlorine is down but is the salt content still high or does the salt content vary with the chlorine content? If it doesn’t, then I will simply go buy a new bottle.

 

[Mdragger88]

That’s what I’ve been doing… 60ml instead of 30ml.

Though question… the chlorine is down but is the salt content still high or does the salt content vary with the chlorine content? If it doesn’t, then I will simply go buy a new bottle.

I’m not sure I understand what you mean- the salt content will be the same I believe. It is an insignificant amount.
Just use up what you have & be sure to buy fresh stuff next time. It doesn’t hurt anything to use old bleach it just takes more of it.

 

[Andrew Montreal]

I’m not sure I understand what you mean- the salt content will be the same I believe. It is an insignificant amount.
Just use up what you have & be sure to buy fresh stuff next time. It doesn’t hurt anything to use old bleach it just takes more of it.

Thank you.

Yes, I meant… is the amount of salt that comes from each ml the same as it was before? In other words, would I be adding more salt than I would be if the chlorine was at its proper percentage?

But as you say, in either case it is a negligible amount.

 

[Mdragger88]

Here’s a handy guide - it doesn’t mention the salt thing though

Breakdown of Bleach Over Time by Storage Temp - Further Reading

www.troublefreepool.com

 

[ajw22]

The salt in the chlorine jug stays the same as the chlorine degrades over time.

In about a year you have a jug with less then 1% chlorine and salt water.

Why are you concerned about the salt level?

 

[Andrew Montreal]

The salt in the chlorine jug stays the same as the chlorine degrades over time.

In about a year you have a jug with less then 1% chlorine and salt water.

Why are you concerned about the salt level?

Being new to all of this, I wondered if the amount of salt that I was adding due to the weakened power of the chlorine would be an issue.

As was mentioned since, it seems that the salt levels are negligible.