Spa Chemical Dosage Charts
Today's post is designed to be a resource for every spa and hot tub owner. This handy spa chemical dosage chart is easy to read, and can even be printed out and kept by your spa for a quick reference! Regular water testing and balancing is key to keeping your spa in tip top shape. So now, let's dive into the world of spa chemicals!
Don't Overdose Your Spa Chemicals
Measure spa adjustment chemicals carefully, using 1/8 cup (1 oz) or 1/4 cup (2 oz) kitchen measuring cups. Another useful tool, the kitchen tablespoon is 1/2 ounce, and the tablespoon is 1/6 ounce, or 0.17 oz. Add small amounts and test again after an hour or so of circulation. Keep a log book of chemical test strip readings and adjustment chemicals used. It can be very helpful in getting to know your spa's chemical personality, and how it reacts to people's chemistry.
Not sure how many gallons is in your spa?
Mathematical formulas exist, but can wrongly estimate the gallons in a portable spa, due to the varied internal seats and shapes. The best way to calculate the number of gallons in a spa is to time exactly how many seconds it takes to fill the entire spa using a stopwatch. Then time the exact amount of time it takes to fill in five gallon bucket, in seconds. Divide Spa Fill time by bucket fill time to determine spa capacity. For example, if it takes 1800 seconds (30 minutes) to fill your spa, and 30 seconds to fill a 5 gallon bucket, then... 1800 ÷ 30 = 60 buckets x 5 gallons = 300 gallons. Another way to find out is to consult the owner's manual, or search online by make/model - if the spa was built by a known manufacturer.
Spa Chemical Dosage Charts
Now, let's get into what the proper balancing chemical doses are for the most common spa sizes. Print out this chart and place it near your spa chemical storage area, for quick reference.
| Spa Chemical | Adjustment | 200 Gallons | 300 Gallons | 500 Gallons |
|---|---|---|---|---|
| pH Up | 6.5 to 7.5 | 1.0 oz | 1.5 oz | 2.5 oz |
| 6.8 to 7.5 | .75 oz | 1.1 oz | 1.9 oz | |
| 7.2 to 7.5 | .25 oz | .4 oz | .65 oz | |
| pH Down | 7.8 to 7.5 | .20 oz | .30 oz | .50 oz |
| 8.0 to 7.5 | .33 oz | .50 oz | .75 oz | |
| 8.2 to 7.5 | .40 oz | .60 oz | 1 oz | |
| Alkalinity Up | 10 ppm | 1 oz | 1.5 oz | 2.5 oz |
| 20 ppm | 2 oz | 3 oz | 5 oz | |
| 30 ppm | 3 oz | 4.5 oz | 7.5 oz | |
| 40 ppm | 4 oz | 6 oz | 10 oz | |
| 50 ppm | 5 oz | 7.5 oz | 12.5 oz | |
| Alkalinity Down | 10 ppm | 1 oz | 1.5 oz | 2.5 oz |
| 20 ppm | 2 oz | 3 oz | 5 oz | |
| 30 ppm | 3 oz | 4.5 oz | 7.5 oz | |
| 40 ppm | 4 oz | 6 oz | 10 oz | |
| 50 ppm | 5 oz | 7.5 oz | 12 oz | |
| Hardness Up | 10 ppm | .4 oz | .6 oz | 1 oz |
| 20 ppm | .8 oz | 1.2 oz | 2 oz | |
| 30 ppm | 1.2 oz | 1.8 oz | 3 oz | |
| 40 ppm | 1.6 oz | 2.4 oz | 4 oz | |
| 50 ppm | 2 oz | 3 oz | 5 oz |
One more tip: Always add one chemical at a time, allowing 15 minutes of circulation before adding other spa chemicals. Adding chemicals right on top of each other can affect the effect!