Calcium Hypochlorite tablets

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pj_may

Active member
Sep 30, 2020
25
UK
Hi,

I’ve been using the bleach method successfully on my SwimSpa and hot tub and I wanted to know if i am going away for a few days whether I can put calcium hypochlorite tablets in the in-line chlorinator?

I want to avoid adding too much CYA (current level 40) and therefore I don’t want to use Dichlor/trichlor tablets. The increase in calcium from the calcium hypochlorite tablets would not be an issue (CH is 215).

I cannot get someone to add bleach in my absence.

The issue I have is that I read that mixing calcium hypochlorite with other forms of chlorine can cause a bad reaction (explosion/fire!). Sorry for the simple question, but would this reaction occur if the different chlorine forms mixed in the water (ie chlorine in the water dissolving calcium hypochlorite tablets in the in-lime chlorinator)?

Should I avoid using calcium hypochlorite tablets and accept that I need to use dichlor/trichlor tablets and deal with the CYA?
Many thanks as always
 
You cannot use cal-hypo tablets in a trichlor tablet feeder. It's specifically designed for the erosion properties of trichlor so won't work properly with cal-hypo and it is unlikely but possible a reaction could occur between trichlor residue in the feeder and the cal-hypo.

Using trichlor for a few days is not going to cause the CYA to jump wildly.
 
How many days? You could just take it to slam level for your cya w/ liquid chlorine & it would probably be fine until you return. If the spa is heated the trichlor can erode quickly and be too acidic.
 
Donldson said:
You cannot use cal-hypo tablets in a trichlor tablet feeder. It's specifically designed for the erosion properties of trichlor so won't work properly with cal-hypo and it is unlikely but possible a reaction could occur between trichlor residue in the feeder and the cal-hypo.

Using trichlor for a few days is not going to cause the CYA to jump wildly.
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Hi thanks for the response.

I don’t use trichlor at all at the moment. As I say I’m using bleach. The cal hypo tabs would be in a standard in line chlorinator not a specialised one.

There wouldn’t be any residual chemicals in the feeder.

Thanks
 
JamesW said:
Unless a feeder is listed to accept a specific chemical, it should not be used.
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Ok thanks, the feeder is ok to use with cal hypo. The question I had was whether the cal hypo would react with the bleach I have been using in the pool itself, not in the feeder.

But it’s ok, I have found out elsewhere that the reaction wouldn’t be an issue in the water.

Thanks
 

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JamesW said:
What feeder do you have?

Where does it say that it's ok to use calcium hypochlorite in the feeder?
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Hi James,
The feeder comes built in. It’s a Hydropool SwimSpa.

The manual just notes it is a Chlorine feeder. I also spoke with the chemical company that supplies the cal hypo tablets and they said there wouldn’t be a problem.

Is there something else I should be aware of?

The feeder has not been used for any other chlorine, it was used for bromine tablets but that finished around 5mths ago and as it is in-line feeder it has been in the water for the last 5 months so I don’t believe there could be any residual chemicals in it.

Thanks
Paul
 
If you toss CalHypo directly into the water there won’t be an issue with the chemistry. The tab will cause a stain if it sits on the liner, but no boom.

If however you insert a CalHypo tab into a feeder that’s had Trichlor in it, there is a chance for a boom. Even if there’s a very small amount of trichlor in the feeder, you will get a chemical reaction.

Lastly, the design of the feeders is different so the feeder dispenses the chemical correctly.
 
How many gallons is the spa?

What is the weight of the calcium hypochlorite tablet?

How much chlorine would be added if the entire tab dissolved?

I suspect that the feeder was not designed or intended to accept calcium hypochlorite.

I don't know for sure, but I wouldn't use it unless you can verify from the feeder maker that it's ok to use.
 
Leebo said:
If you toss CalHypo directly into the water there won’t be an issue with the chemistry. The tab will cause a stain if it sits on the liner, but no boom.

If however you insert a CalHypo tab into a feeder that’s had Trichlor in it, there is a chance for a boom. Even if there’s a very small amount of trichlor in the feeder, you will get a chemical reaction.

Lastly, the design of the feeders is different so the feeder dispenses the chemical correctly.
Click to expand...
Great thanks,

yeah trichlor has never been used.
 
JamesW said:
How many gallons is the spa?

What is the weight of the calcium hypochlorite tablet?

How much chlorine would be added if the entire tab dissolved?

I suspect that the feeder was not designed or intended to accept calcium hypochlorite.

I don't know for sure, but I wouldn't use it unless you can verify from the feeder maker that it's ok to use.
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It’s 9,038 litres, so roughly 2,387 US liquid gallons.

Cal hypo tablets are 10g

I need to confirm the chlorine %. Was checking if any issues before ordering.

I’ll see if I can find out re the in-line feeder.

Given the issue/aversion to cal hypo tablets, would your recommendation be to use dichlor or trichlor tablets for when I go away and accept the increased CYA?

Cheers
 
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