Problem With Chlorine Level

[styro]

Hi everyone,

Recently my spa 350 gal did not get enough chlorine one day.

Same day I add regular amount of chlorine(bleach)

The next day I've notice the difference in Total chlorine and Free chlorine.

The number exceed =1.

Example: Total chlorine 4.23

Free chlorine 3.03

I'm using digital meter(that's way is so accurate)

I try super chlorinate my spa with Lithium Hypo and I added 10ppm of chlorine(around 40g).

The next morning I measure and the difference between T.ch and F.ch was still over 1.

I do not know how to correct that with the chemicals(I prefer not to change the water)

Thanks for any help.

Adam

[Dnepr Dave]

Nothing wrong with those numbers, just wait, they'll come down.

You're not going to fix it by adding more chlorine!

Dave

[styro]

Nothing wrong with those numbers, just wait, they'll come down.

You're not going to fix it by adding more chlorine!

Dave

Actually the numbers are going the apposite direction and is more the 2 weeks now since first time I've notice.

The previous normal difference was only 0.2 - 0.5 not 1.2 and up.

[PaulR]

You can use the bleach to superchlorinate, no need for the lithium hypo (and bleach is a lot cheaper).

Try to keep the FC in the 3-5 range until the CC goes back to normal (or at least no more than 0.5). If you use the dichlor-then-bleach method after each refill (i.e. you have some CYA in the water), you can bring FC up to 10.

I had a situation like this about a month ago, it took about a week to clear up.

--paulr

[styro]

You can use the bleach to superchlorinate, no need for the lithium hypo (and bleach is a lot cheaper).

Try to keep the FC in the 3-5 range until the CC goes back to normal (or at least no more than 0.5). If you use the dichlor-then-bleach method after each refill (i.e. you have some CYA in the water), you can bring FC up to 10.

I had a situation like this about a month ago, it took about a week to clear up.

--paulr

Thanks for replay,

I'd like to understand what you saying.If I keep the chlorine level between 3 to 5 all the time, the problem should clear itself within a week?

It's not in my case.

It is already more then two weeks and the difference betweeen the nummmbers are incrising.

I do use dichlor then bleach method recentley and I try to bring once chlorine level to 10pm like I mention in the bigining.

The only level CYA at he moment I do not know.Could be close to zero since last time I did CyA test was 4 months ago and was 28.

You think maybe that's way the super chlorinate want work for me bringing up 10 chlorine level?

Thanks

Adam

[PaulR]

If my tub behaved like yours is, I would try to hold it at 10ppm for a few days; if the CCs don't clear up or the chlorine demand is over 50%, I'd dump and refill.

--paulr

[styro]

If my tub behaved like yours is, I would try to hold it at 10ppm for a few days; if the CCs don't clear up or the chlorine demand is over 50%, I'd dump and refill.

--paulr

Thanks PaulR,

That's what I would like to hear.

Thanks for shearing your experience.

Adam

[chem geek]

Adam,

You said you've used your spa for 4 months and that you've got a 350 gallon spa. How much do you use the spa? Is it 1 person for 45 minutes every day or 2 people for 30 minutes every day, etc.? The reason I ask is that the Dichlor-then-bleach method helps extend the water by around twice as long as Dichlor-only, but not forever. There can be a buildup of slow-to-oxidize contaminants and over time this can increase the chlorine demand. Though keeping the chlorine at a higher shock level helps burn through those contaminants, it can still get to a point where it's better to just replace the water.

The standard Water Replacement Interval (WRI) for spas is:

WRI = (1/3) x (Spa Volume in U.S. Gallons) / (Number of Bathers)

where it is presumed that the bather time in the spa is around 20-30 minutes. This results in only 39-58 days for one person-hour of soaking every day in 350 gallons. With Dichlor-then-bleach, this extends to around 80-120 days for one person-hour per day. In practice, many spa users do better than this, but 4 months is quite some time for a spa unless it's not used every day.

The only other way to practically extend the water is to have more powerful oxidizer systems. An ozonator can help as can the use of enzymes. Even so, the continued use of chlorine builds up salt and in the above example at 7 ppm FC per person-hour in 350 gallons, after 4 months that is an increase in salt (from bleach) of almost 1400 ppm.

Richard

[styro]

Adam,

You said you've used your spa for 4 months and that you've got a 350 gallon spa. How much do you use the spa? Is it 1 person for 45 minutes every day or 2 people for 30 minutes every day, etc.? The reason I ask is that the Dichlor-then-bleach method helps extend the water by around twice as long as Dichlor-only, but not forever. There can be a buildup of slow-to-oxidize contaminants and over time this can increase the chlorine demand. Though keeping the chlorine at a higher shock level helps burn through those contaminants, it can still get to a point where it's better to just replace the water.

The standard Water Replacement Interval (WRI) for spas is:

WRI = (1/3) x (Spa Volume in U.S. Gallons) / (Number of Bathers)

where it is presumed that the bather time in the spa is around 20-30 minutes. This results in only 39-58 days for one person-hour of soaking every day in 350 gallons. With Dichlor-then-bleach, this extends to around 80-120 days for one person-hour per day. In practice, many spa users do better than this, but 4 months is quite some time for a spa unless it's not used every day.

The only other way to practically extend the water is to have more powerful oxidizer systems. An ozonator can help as can the use of enzymes. Even so, the continued use of chlorine builds up salt and in the above example at 7 ppm FC per person-hour in 350 gallons, after 4 months that is an increase in salt (from bleach) of almost 1400 ppm.

Richard

Thanks Richard,

I did change my water last time to be exact in November before cold winter days since I'm in Canada, Ontario.

Dichlor method I started in the middle of December with bleach mostly and Lithium once in the wile.

During the winter time I was using the spa almost every second day 20-30 min each time.

I'm glad the winter is over and is time to change the water.

I mist one time to add the chlorine to the water and chlorine level become "0" for about a day.

But I was surprise when I try to superchlorinate the water by increasing the chlorine level to 10 ppm (using Lithium) and nothing happen.( no change)

That's way I started this topic.

Thanks for technical explanations.

Adam

[chem geek]

OK thanks. Well, that's not too much usage so it does sound like the one day without sufficient chlorine led to some bacteria growth that may have formed biofilms that now result in higher CC. Superchlorination or sustained shock levels should get rid of that, but if you decide to replace the water that's fine too. I would do a decontamination procedure when you change the water, just to be on the safe side.

[styro]

OK thanks. Well, that's not too much usage so it does sound like the one day without sufficient chlorine led to some bacteria growth that may have formed biofilms that now result in higher CC. Superchlorination or sustained shock levels should get rid of that, but if you decide to replace the water that's fine too. I would do a decontamination procedure when you change the water, just to be on the safe side.

Can you please repost decontamination procedure.

Thanks

Adam

[chem geek]

The decontamination procedure is described here.