Why do we not use shock?

[Crepes]

Yesterday my wife went to the pool store and picked up shock and chlorine tablets. Oh no! I was pretty mad because we had talked before and agreed that bleach is what everyone here said to use, so that's what we should use. But then she asked why we can't just use shock, and I really didn't have an answer. I had read here many times that bleach is the way to go, but I don't think I've ever seen a reason why we can't use shock. I mean, 4 of my adjacent neighbors all have pools, all use shock, and all have crystal clear pools. Why shouldn't I?

 

[Texas Splash]

Shock is a term people use to simply increase the FC quickly as in a one-time application. This "spike" in FC is usually recommended by pool stores who sell convenient "bags" of products to do that. Those bags of shock might contain cal-hypo or stabilizer as a sub-ingredient. Can they be used? ... yes. Are they intended for daily chlorination? .... no. Here at TFP we generally do not "shock" a pool for a one-time event like you see at pool stores. We are always crystal (TFP) clear. If we have a problem, we "maintain" that FC level by doing a SLAM Process. So that's really the difference.

Much in the same manner, tabs increase CYA, we know that. It doesn't mean thy can never be used. They have their place, but the owner needs to know where their current CYA level is before using tabs for too long so they understand how long they can use them.

 

[Jimrahbe]

C,

You can use whatever you want in your pool, including tabs and shock... the main problem is that these products will increase your CYA levels to a point that makes the chlorine ineffective and then your pool will turn green.

The key is not to just use Liquid Chlorine/bleach, but to test your pool water and then understand what you should or should not add to your pool. If your CYA is low, then using pool store shock and tabs is just fine.. Except for the cost of course.. But if your CYA is already at 90, then continually adding pool store products is not a good idea...

One approach is to use pool store products until the CYA gets too high and then drain and start over.. Not the best approach in my mind, but it will work..

Thanks for posting,

Jim R.

 

[Donldson]

Chlorine is a gas, it must be attached to something to make it not-a-gas. To make it liquid only involves salt and water. So when you add it to your pool it introduces nothing but salt and chlorine. Simple.

To make it solid, it gets more complicated. Salt and chlorine are still in the mix, but instead of water it is bound to another chemical. For the chemicals trichlor and dichlor it is bound to CYA molecules. This causes CYA buildup which severely blunts the effectiveness of chlorine. CYA in a pool is one of those things were too little is bad and too much is really bad, but in a certain range it is very helpful.

Calcium hypochlorite is chlorine bound to calcium. This will increase your calcium level which can be a problem as it builds up. Also cal-hypo dissolves somewhat slowly and can sit on the liner if you aren't careful and stain it.

Then there is lithium hypochlorite, but if she didn't bring it home in an armored car then you didn't get lithium hypochlorite

But the most troubling thing I see in your post is that you just called it "shock". One of the most important things about TFP is knowing what you are adding to your pool. Just dumping in chemicals without knowing what they are going to do is more of a pool store "buy this and don't ask questions" technique. TFP is not specifically about what chemicals you can and can't add to your pool. Only that you know what you are adding to your pool, what it will do to your levels, and what that means in the long run.

 

[Crepes]

Awesome, thank you all very much!

I know my CYA is 70-80 already and will need a partial drain. Definitely don't want to be adding more of that. Looks like we'll be returning both of these to the store. I should've specified shock (the product), whoops!

 

[skimmerswimmer]

If your CYA level is low, it is certainly OK to use the chlorinating pucks to add FC and stabilizer over time, you just need to be able to accurately test your water and know what it needs and what FC levels need to be maintained for your corresponding CYA level. For the bags of shock (typically calcium hypochlorite), they add calcium and can raise your CH level over time. If your CH is already high (>400 ppm), then adding more can cause scaling problems. If you have some bags of this type of shock laying around and your FC is low and your CH is on the low end of the range, it certainly wont hurt to use the right amount in your pool, but you need to know how much it will raise your FC, CH and/or CYA. You can use the Pool Math app linked at the top of the page to determinei this.

TFP advocates pool owners doing their own testing using one of the recommended test kits, and adding only what a pool needs when it needs it. Many TFP members chlorinate their pools by adding liquid chlorine daily (and sometimes multiple times per day using automated chlorinating pumps) or using salt water generators to continuously add small amounts of chlorine to their pools in order to maintain proper FC levels.

You can use whatever you want, just make sure you know what you're adding and how it is affecting your pool chemistry.

The most important part is knowing what your target FC level is and keeping it there:
Pool School - Chlorine / CYA Chart

 

[zea3]

Another way of putting it, is that TFP is all about using the right tool for the job. The TFP pool care method is based on accurate testing. When you know what you have in the water, you know what you need to add to keep it clean. People who use dry chlorine like powdered "shock" and tablets typically add them one time per week. The typical stabilized powdered shock raises the FC 10 ppm in 10,000 gallons of water, and raises the CYA by 6ppm. The FC will burn off but the CYA remains and builds up over time. For a 12 week swim season, 12 weeks of "shock" treatment adds 72 ppm of CYA to the pool. That is in addition to whatever the CYA level was at the beginning of pool season. The recommended range of CYA in a manually chlorinated pool is 30-50 ppm. It you keep say 3 tablets in a floater as well, they add an additional 3 ppm of CYA per tablet. If you use 3 tablets per week that is 9 ppm per week, and over 12 weeks that is 108 ppm of CYA. The week use of "shock" and tablets will leave you with 180 ppm of CYA, + whatever the starting CYA level was.

About the time you hit 100 ppm of CYA you will notice the water is getting cloudy, and typical pool store advice will tell you to add a second bag of "shock". That will clear it temporarily, but you have also increased the dose of CYA along with it. This is why we say liquid chlorine or bleach is the right tool for the job of chlorinating your pool. It doesn't add CYA to the water that you don't need. We recommend daily testing and dosing the pool only for what it needs.

Your friends who use "shock" and tablets may have pools that look ok at first, but they probably have at least one algae outbreak per season that requires additional pool store products to treat the pool. The pool store may tell them they have "chlorine lock" or "old water" (pool industry terms for high CYA) and that it must be drained and refilled to eliminate the problem. That is because the only way to get rid of excess CYA is to replace the water. In some climates where you drain below the skimmer and close for the winter and back wash a sand filter frequently during the season, you may replace enough water to keep the CYA levels down.

Sorry for the long winded answer, but this is why we use bleach.

 

[Propbndr]

You can get chlorine “logs” that do not contain stabilizer. They cost about the same as the ones with stabilizer. The brand I keep on hand are compressed chlorine in open ended plastic tubes. They must be used in the skimmer basket, floaters will not work, because they must have a large flow for them to dissolve. The up side for me is that I can keep 5 pounds them on hand for emergencies, such as my SWG dying, without having to worry about liquid bleach expiring. And like a SWG, they continuously add chlorine. The only down side is that your filter must be run 24/7 while they are in the skimmer.

 

[pooldv]

What does the label on those "logs" say? The chlorine has to be bound to something, usually either CYA or calcium. Most sticks, logs, pucks are either cal-hypo or trichlor. Most powders are dichlor or cal-hypo.

More here, Pool School - How to Chlorinate Your Pool

 

[Propbndr]

What does the label on those "logs" say? The chlorine has to be bound to something, usually either CYA or calcium. Most sticks, logs, pucks are either cal-hypo or trichlor. Most powders are dichlor or cal-hypo.

More here, Pool School - How to Chlorinate Your Pool

The brand is Pool life. Calcium Hypochlorite is the main ingredient.

From their website:

Chlorinators (yellow lids)
Our exclusive line of chlorinators (yellow lids) help you ensure that its beauty is easily maintained. poolife® chlorinators are calcium hypochlorite based and designed to effectively guard from bacteria, algae and other contaminants. poolife® chlorinators are available in caplet and granular forms. The granular chlorinator products dissolve quickly, chlorinate with fast results and will NOT cause overstabilization - even with prolonged use. There is no need to pre-dissolve poolife® granular chlorinators before use. The caplets have been designed for use in skimmers and dissolve slowly for continuous chlorination. Always read product label directions before use.

IMO, it is refreshing that a pool chemical company realizes that you can over stabilize your pool.

 

[zea3]

You will need to keep an eye on your calcium and pH levels so you don't develop scale.

 

[frustratedpoolmom]

Cal-Hypo tabs can be used, so long as the user understands how to monitor their calcium levels and pH, because a combination of high pH and Calcium can result in scale issues.

 

[pooldv]

The brand is Pool life. Calcium Hypochlorite is the main ingredient.

IMO, it is refreshing that a pool chemical company realizes that you can over stabilize your pool.

Yes, it is for sure!

 

[YippeeSkippy]

Something not yet mentioned in this thread is that different places and people call different items "Shock". Some places sell liquid chlorine and call that "shock", others call packets of CYA or Calcium containing chlorine granules "shock".

So not knowing what you bought its hard to know if it is of any use to you.

Learning what the actually chemicals are you're putting into your pool is always a good idea. And recognize that pool companies like Clorox, and pool stores are in the business of selling you "stuff" whether you need it or not. Clorox with their miserable test strips is another way they try to rope you in to using their products since they're telling you which of their products to go buy. Again, when you might really not use it!

Go to Walmart's pool section and look at their 10% liquid pool chlorine. That may be your best buy. Nothing in there but chlorine and a little salt.

Maddie

- - - Updated - - -

IMO, it is refreshing that a pool chemical company realizes that you can over stabilize your pool.

Yes, it is for sure!

Yet conveniently never mentioning the risk of having too much calcium = scale buildup.

<shrug>

 

[wilkj1]

Well if i had not found TFP i would still be dumping "stuff" in my pool. Man was i uneducated and still have lots to learn . It is so hard to not go back to the "pool guys" i fired and let them have it good. My pool is TF and perfect thanks again TFP. That is why i will try to support this site forever. Btw i do not miss coming home to a green mess growing on my pool walls and hearing well we can come next monday................ yes you really do care about my pool right! NOT......Thank you Thank you TFP.

 

[pooldv]

You're welcome! And thanks for supporting TFP!

 

[CrisVH]

I use everything and have no problems as long as I keep the CYA in check. I’ll shock once a month with dichlor or cal-hypo granules, use trichlor tabs in an inline chlorinator and occasionally use liquid chlorine instead of tabs when the CYA starts to creep up. I just use test strips. No problems so far ((fingers crossed)). If you are good figuring out the chemistry, you’ll know what to do to keep that water clear. I like the convenience of tabs bc I can’t spend every day adding liquid chlorine, I don’t have that kind of time and no pool service. But just using tabs forever will definitely raise the CYA too much and cause problems. You need to take a break from trichlor.

 

[Donldson]

I like the convenience of tabs bc I can’t spend every day adding liquid chlorine, I don’t have that kind of time and no pool service.

It would have taken you less time to test and dose your pool than it did to make this post. So if you really don't have that kind of time you definitely shouldn't be wasting it by posting about how you don't bother to follow anything we teach.

 

[tim5055]

I should've specified shock (the product), whoops!

Liquid shock. She did get shock, just a solid form. Unfortunately the pool industry has evolved into sales by scare tactics, misdirection, misinformation and marketing hype.

 

[Donldson]

IMO, it is refreshing that a pool chemical company realizes that you can over stabilize your pool.

I'm not so optimistic about it. Rather I see it as another way to get money out of people. First they sell trichlor which raises the CYA. Then they sell algaecide to mask the overstabilization problem. Then they sell these, which raises the CH. Then they sell the scale inhibitor. Then, when they have nothing left to sell, they can tell the customer that their TDS is just too high and it is time to drain and start over. Probably sell some fresh sand or a new cartridge for their filter to go with that water change as well.

They charge you for the cure to the disease they sold you...