Pool guy here. This product contains Sodium Dichloro-s-Triazinetrione which is a pool sanitizer that releases chlorine into your pool water for the purpose of killing bacteria and preventing algae from forming. As the name suggests, Sodium Dichloro-s-Triazinetrione is Sodium based. This product is designed to be used in a SALTWATER pool or spa environment. Something that's important to note - the "available chlorine" found in this product is approximately 55% which is quite low compared to other sanitizers. For instance, Cal-Hypo has an available chlorine content of about 68%. And TriChlor tablets have an available chlorine content of about 90%. As you can see, it's not reasonable to expect the same results from the same volume of these three products. Also worth noting, Cal-hypo is calcium based and is designed to be used in gunite pools. Trichlor is designed to be used in freshwater and saltwater pools - and pools having vinyl and gunite surfaces. Also, Sodium Dichlor and Trichlor both contain CYA or cyanuric acid which acts as a stabilizer or conditioner that protects the chlorine from being burned off by the sun. This is a very important feature to know about. Without CYA in your pool water, most of your chlorine will disappear in a day or less. On the downside, CYA accumulates in a pool over time as more sanitizer is added. When the CYA level gets above a certain limit, the chlorine in your pool is rendered ineffective no matter how much chlorine you've added. The only way to reduce the amount of CYA is by partially draining and refilling the pool with fresh water. Please understand, there are many different physical and chemical aspects involved in keeping your pool water clean, clear and safe. Anyone can "shock" their pool. But it takes an understanding of your entire pool environment to effectively treat and maintain your pool safely and economically. Just as important as balancing your pool water chemistry is to ensure your pool water circulation and filtration systems are setup and working correctly. You can have a pool whose water is perfectly balanced (free chlorine, combined chlorine, pH, total alkalinity, cyanuric acid, calcium, etc) are all within spec. But if your pump isn't circulating your pool water properly, your pool will in all likelihood turn green in a matter of days. The same is true for having an ineffective filtration system. If you pool filter hasn't been properly serviced, your filter will get jammed up with bacteria that will contaminate your perfectly balanced and circulating pool water. If you find yourself in a situation of not knowing what you should do, I suggest calling a good pool guy in your area. Ask your neighbors who to call - or who NOT to call! And have him or her come out to help get your pool squared away. And with time, you can start taking over the maintenance and management of your own pool should you decide to do so. My two cents!

Excellent packaging

I have been purchasing this item for 3 seasons now and have never had anything but great results. Products I purchased prior to that were always hit and miss (similar to many of the reviews here) but never an issue with this one. On my way to Sam's to buy a new one now. Great price too!

We have a 50 year old concrete pool measuring 25 x 50 by 8 ft deep with an antiquated skimmer system, so tablets are out of the question. All other brands of granular chlorine are calcium hypochlorite with only about 65% active ingredients. This brand from Sam's Club has been providing us sparkling water for several years now and it is 99% active sodium dichloro-s-triazinine, which is what the tablets are made from and it dissolves instantly and leaves no residue on the bottom like the other aforementioned products. We use it for shock and daily maintenance as required. And the price is great, not to mention we need to use 35% less.

Good price but poor product. I used 2 buckets of this in a season and a half (in Georgia) before I realized this product is very weak and does not get the job done. I used to buy Poolbrand chlorine at Sams and never had an issue. I've been maintaining my pool for almost 20 years and never run into a problem with any brand of chlorine until using members mark brand. Oh, by the way, I returned half of the second bucket and sams gave me a refund.

MembersMark pool chlorine is awesome. It works very well.

Good price, free delivery

Price jumped 2/100 dollars. How ridiculous is that corporate greed is all that is!

Reluctantly bought this bc I need it for the summer.

Love this stuff for our pool thank you Sam's