In The SwimPool Shock – 68% Cal-Hypo Granular Sanitizer for Crystal Clear Water – Defends Against Bacteria, Algae, and Microorganisms - 25 Pounds

This pool chemical works very well, and requires much less volume of chemical. Amazon has it at a much lower price than pool supply or big box stores.

Arrived quickly, good quality. Cheaper than pool store!

The media could not be loaded. Wow, so simple! I have no previous knowledge of pool chemicals, but I did some brief research, bought some Easytest strips, checked the levels, and ordered the 1lb bags of this In The Swim shock for my pool. I poured it in, spreading it evenly around the pool, I have 2 floating chlorine tablets in my pool as well, flipped on the pool pump, and within 24 hours the algae (green) was gone! To clarify it, I’m still waiting on the sodium bicarbonate, but the shock from In The Swim did exactly what I had hoped for the algae and in a very reasonable time frame. It was simple, small enough that I could just cut it open and pour it in, and all of the bags seemed to be in good condition with nothing spilled into the box.

I was really Surprise by the efficiency of the shock. It was very effective with who which is 25,000 gallons. I thought it did a very good job and I'm very pleased with it.

As long as you are NOT paying shipping expenses (have Amazon Prime), this is the cheapest way to add chlorine to your pool, AND it adds calcium, AND you are not raising Cyanuric Acid (CYA), which should never exceed "30" for a residential pool. This product WILL also stabilize and raise pH, so you can buy less bicarbonate and reduce pH fluctuation. This product is a NO brainer as the best cheap source of chlorine for ANY pool (unless you do not want to increase water hardness (calcium) ).Stable at a minimum of 65% cholorine for well over 1 year, it does not go bad like liquid chlorine, which loses 1/2% + concentration per month! By the time you buy that liquid chlorine, it has probably already degraded a couple percent. The production date on the liquid chlorine is usually at least 50 days old. Learn to read the production date on liquid chlorine sold at HD or Lowe's and do not buy if it is old. The first digits are the year, the next set of digits is the day of the year. For example, a stamp that begins ...20366 will be December 31, 2020.NEVER toss powdered chemicals into pool unless they are pure chlorine. Powdered chemicals just sink and do who knows what to your pool surface. Always mix first in 5 gal bucket, stir, then add to water. I do this a couple times to fully dissolve the calcium. OF COURSE the water will go cloudy - it is *Calcium* HypoChlorite, but the cloudiness only lasts a short time.Most pools do not have enough calcium hardness - I keep mine well above 400 so I can keep the pH low for better chlorine efficacy. This product also avoids the cost of separately buying a calcium enhancer for the pool. Because it has no stabilizer it will not raise your CYA.Final point : Focus on maintaining LSI. This keeps the water from being corrosive or depositing calcium on the surface. I recommend the free Orenda app.Plus -- unlike liquid chlorine, this does not make the water taste salty, is easy to store, is stable, adds hardness, is cheaper source of Chlorine, does NOT add CYA!Minus -- mixing it up before adding to pool takes a couple minutes you have to be careful to avoid splashing, which will ruin your clothes. You also have to cut the packet with a knife or scissors and avoid spilling any.Highly recommended

Cal Hypo Shock. 70%. Works. Cheap.

A must have on hand. I generally use professional gallon chlorine because of it's purity and lack of stabilizer or CA, but this stuff is great to have on hand. Also, it has the benefit of lasting longer the gallon chlorine, especially if you are using a bromine treatment for algae. This is a must have imo, and this brand is top quality and %. If you are on well water you do not want any higher then 68%, it will excite copper and iron ions if you do and you will have another problem. You also dont want less, as in those in the 50's % chlorine are completely ineffective. For some reason I still like the gallon stuff from pool store, not the ones in a box, the ones in a crate, best stuff but is about double the cost of this stuff when it'son sale. Store up this product lasts at least a year in a cool dark place. glad to get this from amazon so not to buy elsewhere.

My pool was starting to get algae and the algaecide I use requires a certain balance of chlorine PPM, and PH to be effective. I only had one bottle of liquid chlorine so I put that in and two pounds of shock, broadcast by hand. two hours later I added two cups of acid. After two more hours I added the algaecide that uses the chlorine in getting rid of the acid. Next morning, no algae and, as the description of the product mentioned, crystal clear water. As for the shock, it dissolved quickly, and unlike other shocks or powdered chlorine, all of it was dissolved and none of it was floating on the surface.