Liquid or Granular Chlorine System?

by Ray Gelli
(Redwood City, CA 94062)

I'm looking at an automatic pool sensitization system from Jandy. Not sure If I should get the liquide chlorine or the granulare systems. It seems easier and cheaper to use liquid chlorine and Muratic acid systems since I have plenty of big equipment room with room for a couple 5 gal tanks.

I am not a high tech person to begin with and want a reliable easy to maintain system.

Is the Watermatic system with adjustable peristaltic pumps and the Chemlink C1900 controller for me. I have a new 26000 pool.

Or is the hybrid granular chlorine with liquid pH C1500 controller.

Im confused.

Thanks for the question Ray

There are many products out there and while I have limited experience with the exact models you cited I can say that I've had very good personal experience with Zodiac and Jandy parts and systems.

I had an ORP (Oxidation- Reduction-Potential) system when I was the pool operator at the Y and it worked very well. Low maintenance and it could handle 5000 - 6000 swimmers per month. Once we installed it I simply checked it once per week and made sure it was calibrated correctly. I seriously doubt your pool will be handling that amount of swimmers.

I believe many systems can handle either granular or liquid chlorine. If we can keep it simple, you want a controller that can maintain the sanitizer levels and pH balance by measuring the ORP and pH balance of the water. The Jandy ChemLink ORP/pH Interface - C1900 would be a good choice for that, however, this is only my opinion.

Next is to either use granular or liquid. You're right on the money when you say liquid chlorine. I wouldn't use granular for a couple of reasons.

First is you're adding hardness to the water. It's called calcium hypochlorite for a reason and being you're in the great state of CA you probably have high hardness fill water. Granular wouldn't be a good choice.

Next is calcium hypo has a pH of 12. This means it's slowly adding pH to the water which will cause you to use more acid to keep the pH in the proper range of 7.2 - 7.8. Liquid chlorine has a pH of around 8 so the pool water pH won't increase as quickly.

I hope this has answered your question to your satisfaction.


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Can I Make Liquid Shock From Powdered Chlorine Shock?

by Frank Garcia

Is it possible to make liquid shock from powdered shock. I use liquid shock to wash houses but this time of the year it's hard to get were powerd is readly available.

Thank you

Thanks for the question Frank

If I'm reading the question correctly, the answer is yes you can make a liquid shock out of a powder. Shock is nothing more than chlorine. It might be a little more powerful, but it's still chlorine, and possibly some inert ingredients. There's really nothing special about products that call themselves "shock" per se.

The most common form of granular chlorine is called calcium hypochlorite. Here's the link to my page:

Calcium Hypochlorite

One pound of cal. hypo. is equivalent to 1 gallon of liquid chlorine. I personally wouldn't buy anything over expensive because of a fancy name. Get chlorine granules and you should be fine.

Be sure to add the chemical to the water, not the other way around. Get a 5 gallon bucket and stir with a 3 - 4 ft. PVC pipe. Obviously with experience washing houses you understand to have items designated for certain jobs. Only use the bucket for the intended purpose to lessen the possibility of cross-contamination.

Hope this answers your question and have a wonderful day.


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Calcium Hypochlorite & Granular chlorine

by Dave

Comment about Calcium Hypochlorite And granular chlorine.

While at my local pool store to buy some chlorine to close my pool in winter, I remembered this site. The website said to get granular chlorine. I bought it and it was sure easier than those gallon jugs I used before.

I'm not too worried about the higher pH level because our tap water is already pretty low, about 7.2. I went to the pool winterization page and that was full of really good information.

Thanks for all the great stuff on this site. I will be back for more.

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Sodium Hypochlorite (liquid) vs. Calcium Hypochlorite (powder) Chlorine

by Frank
(North Carolina)

I have several questions. I have been looking for sodium hypochlorite, and I can not find it in powder or grandular form. Is it made for sale, and who has it? What is the difference between the two chlorines?

Why is household bleach made mostly for the sodium, and pool shock made from mostly calcium?

Thanks for your help.


Thanks for the follow up Frank

I've already answered your questions here:

Can I Make Liquid Shock From Powdered Chlorine Shock?

I have several pages where you can ask questions. When you ask a new question on a page, you'll need to fill out the form completely, including your email. This will automatically alert you when your question is answered. When you comment on an already existing question, you'll need to follow up. There's no alert email. When a question is asked on the "Ask The Expert" or "Submit Questions" on the side bar, the email comes directly to me.

The difference between the two kinds of chlorine: Sodium hypo is liquid and calcium hypo is granules. Liquid has about 16% active chlorine and the granules are about 68%. The calcium is what binds the chlorine.

If you have hard fill water, over 150 - 200ppm, use liquid. If you use calcium, you'll be adding more hardness to the water. Liquid is heavier than the granules. 1lb. of granules = 8 lbs. of liquid. I used granules when I did pools in Arizona for this very reason. It's safer, lighter, and easier to store.

I never shocked any pools until I became the pool operator for the YMCA indoor pool. If you keep the chemical levels correct, there's no need to shock. Only shock when the combined chlorine level gets above 0.6ppm for 3 consecutive days.

Liquid is also better for shocking, not because it chlorinates better, but if you use calcium hypo you're going to have a thin layer of calcium on the bottom of the pool that will need to be vacuumed up.

Hope this clears it up for you.


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Over Chlorinated Pool Water

by Marcel Antat

I need your advice, my pool staff using a lot of HTH and the bottom of the pool still yellowish.

They dissolved 50 kilo of hth calcium hypochlorite at 0900hrs in the bucket and they put water to chlorine and leave it outside in the sun without shelter on the pool deck which have an evaporated temperature 45 to 50 degrees and outside temperature 35 degrees, the way they put it at 1800hrs directly in the balancing tank.

Do you think that it still strong in efficiency strong to disinfectant and now we have problem staph aureus, total coliform, aerobic colony count. Can I do shock treatment by putting calcium hypochlorite granular directly to the pool.

Hi Marcel. We're on the standard weights but according to my calculations you put in 110 lbs. of cal hypo. Unless you have an extremely large pool that's a very large amount. Temps at 45 - 50 F is different than 45 C.

Cal hypo is an unstabilized form of chlorine and its effectiveness is dependent on the CYA level and pH. Too high or low CYA will render the chlorine ineffective. High pH will also reduce its effectiveness. The only way to test the chlorine is to add it to the pool, filter for 8 hours, then retest. I'd also test the combined chlorine as well. This is a good indication to whether the chlorine is working or not.

You can shock the pool with cal hypo but that will leave a calcium film on the bottom of the pool that will need to be vacuumed. I prefer liquid chlorine. If you add cal hypo directly to the pool you'll need to sweep very well because much of it will settle to the bottom.


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