Pool Basics 2808PB Calcium Hardness Increaser for Pools, 8-Pound

Works fine in my hot tub, at a fraction of the cost of small bottle of liquid that I used before.

works as described, dissolves quick. Good and cheap product.

We recently moved to a new home and it had an outdoor hot tub (aprox. 250 Gal capacity). As I refilled it from outdoor hose I realized that water by default goes thru water softener (not smartest setup) so it was extremely soft. I purchased this Hardness increaser and was a little confused by directions as they were for thousands of gallons of water (for pools). By extermination I found that about 3 cups (not standard cup, but rather cup that's on top of the bottle) increased my spa's hardness just to the perfect level! You do need to dissolve it in bucket of water before pouring into the spa as per instructions.I couldn't bought much smaller quantity, but I also have a pool (which is yet to be filled and opened) so it should work for both :)

It's a chemical. It works. Enough said... You can probably find the same stuff locally, but this was for convenience. It works....

wonderful!

Works fine. These kinds of products are generally the same throughout the industry, so I shop by price. I bought this and shipped overnight, and 25 lb. at free shipping, only because I needed some immediately, but not the whole season worth. Occasionally, a calcium product comes in that doesn't dissolve well, but this is not one of them. Served just fine.

I can't recommend it for hot tubs; it's chunky, rock-like size calcium. Perhaps it doesn't do any damage but because of its size it'll sit a while before it absorbs into the water

does the job at a great price . . .less expensive than pool supply houses. Note - this works for both the swimming pool and hot tubs. You can buy a smaller container of this labeled for hot tubs at three times the price, but you're just throwing your money away.