I’ve learned a few things about swimming pools after owning one for 12 years.  #1, pools are a huge money pit.  #2, pool chemicals, particularly when sold as such, are extremely expensive.  And #3, for a lot of pool chemicals, you can save a significant amount of money by purchasing the equivalent product from an alternative source.  You just have to know where to look.

This write-up is geared towards concrete/plaster pools with salt water Chlorine generators, but much of the info is applicable to all pools.

Chlorine

If your pool doesn’t have a salt water generator (SWG), liquid chlorine is generally the most economical way to chlorinate.  The trade-off is that it’s more labor intensive than using Trichlor pucks, and the liquid chlorine has a shorter shelf life.

For pools with a SWG, it’s still a good idea to keep some liquid chlorine on hand for shocking, opening/closing the pool, and off-season maintenance.

Standard Clorox bleach is the same thing as liquid pool chlorine, just in a lower concentration. Buy standard, plain old Ultra Clorox, with no added fragrances or other stuff. Check the label for concentration; you want at least 6.25% Sodium Hypochlorite. 2 parts of this is equivalent to 1 part liquid pool chlorine, which is 12.5% Sodium Hypochlorite. The weaker concentration also has a longer shelf life.  Look for house brands at stores like Wal*Mart, but make sure the label clearly shows the product concentration.

In my area, it is still more cost-effective to buy 12.5% pool chlorine in 5-gallon jugs. Namco Pool and Patio sells them for $17 (+ $6 refundable jug deposit) as of 2010, which works out to $3.40/gallon. At this price, you’d have to find Ultra Clorox at $1.70/gallon to get the same value.

Salt

If you have a SWG pool, you’ll periodically need to add salt to it.  Look for “solar salt” at Home Depot or Lowes, in 40lb and 80lb blue bags. It is sold for use with water softeners, and typically goes for around $5 for 40lbs. Look in the aisle with the water heaters and water softener systems. There has never been a discount for buying the 80lb bags, so I get the 40lb bags for ease in handling.  Don’t use table salt; it contains iodine and you don’t want that in your pool.

Alkalinity Increaser

Arm & Hammer Baking Soda (Sodium Bicarbonate) is the same stuff as the “Alkalinity Increaser” the pool stores sell. We buy the big bags of it sold at warehouse clubs. It’s typically less than half the price of the pool store stuff.  Another bonus: it’s classified as a food/grocery product, so in most states, you won’t pay sales tax on it either.

pH Reducer

If you have a plaster pool and/or use a SWG or any kind of hypochlorite product (liquid chlorine or Calcium Hypochlorite powder), your pool’s pH will tend to rise over time and you’ll need to periodically add acid to lower it.  Look for Muriatic Acid at Lowes, in the paint section near the turpentine and paint thinner. It is sold in gallon jugs. I have never found it at Home Depot.  Muriatic acid is significantly cheaper than “dry acid” or sodium bisulfate, which is typically sold for pools.  The trade-off is that it’s more hazardous to store, so be careful with it.  Be careful: you want the stuff with the orange label, not the “safer muriatic acid” with the green label.

One year at Home Depot, I scored several 8-pound jugs of Sodium Bisulfate (dry acid) at around $2.50 a jug. This is an amazing deal, probably cheaper than wholesale. I think it was around December. You can’t count on finding a deal like this every year, but sometimes it does pay to check the pool sections in big box stores during the off season.

Calcium Hardness Increaser

In plaster pools, it’s important to keep the water from getting too soft, or it will become corrosive to the pool plaster.  Look for bags of Calcium Chloride ice melter at the big box stores in the winter. In early 2010, I found 50lb bags of this at Home Depot for around $17, which is about ¼ the price you’d pay for the same stuff at a pool store. The catch is, you have to read the label carefully. You want pure Calcium Chloride, and it can’t be mixed in with any other chemical. Most winters, the box stores sell blends of different chemicals, which are cheaper by the pound than Calcium Chloride, but you don’t want to put them in your pool.

Cyanuric Acid

Sold as “stabilizer/conditioner.” Can’t really cheat with this stuff, unfortunately, as it doesn’t have many applications outside swimming pools. It often sells at $4-5/lb at pool stores. If I had an opportunity to buy this at wholesale, I’d stock up. But lacking that, I’ve shopped around for online deals, and the best price I’ve found currently is at Inyo Pool Products, at $70 for a 25lb pail. That’s $2.80/lb, plus a $5 handling fee per order. Dry cyanuric acid lasts forever, so stock up.

Test Kit Reagent Refills

These really add up, particularly the good quality reagents from Taylor. Surprisingly, the best online prices I’ve found are at Leslie’s Poolmart, where shipping is free for orders over $50.  As of 2011, you can also buy refills directly from Taylor on their web site.