Muriatic Acid vs. Dry Acid: Which Should You Use?

Both muriatic acid and dry acid (sodium bisulfate) lower pH and total alkalinity. They do the same job, but they're different to use, store, and buy. Here's how to decide.

Muriatic Acid (Hydrochloric Acid)

Muriatic acid is a liquid, typically sold in 1-gallon jugs at 31.45% concentration. It's the pool professional's choice for a reason: it's inexpensive, fast-acting, and doesn't add anything extra to your water. A gallon costs about $8-12 at most hardware stores.

The downsides: it produces strong fumes that can irritate your lungs and eyes. It can burn skin on contact. It corrodes metal if stored nearby (the fumes alone can rust tools in a closed garage). And it needs to be handled with care.

Dry Acid (Sodium Bisulfate)

Dry acid is a granular powder, sold in bags or buckets. It's much easier to handle than liquid acid because there are no fumes (in its dry form) and no splashing risk. It's also easier to store safely.

The downsides: it costs significantly more per dose. It dissolves slower than liquid acid, so the effect takes longer. It adds sodium and sulfate to your water, which isn't ideal for saltwater pools or pools on well water. And the granules can damage pool surfaces if they settle before dissolving.

Cost Comparison

To lower pH by the same amount in a 10,000-gallon pool, you need about 16 fluid ounces of muriatic acid (about $1 worth from a gallon jug) or about 12 ounces of sodium bisulfate (about $3-4 from a typical pool store container). Over a season, muriatic acid saves significant money, especially in pools where pH rises frequently.

Which Should You Choose?

If you're comfortable handling liquid chemicals and have outdoor storage away from metal, use muriatic acid. It's cheaper, faster, and cleaner (doesn't add extra minerals).

If you're new to pool care, don't have good storage options, or are uncomfortable with liquid acid, start with dry acid. The extra cost is worth the peace of mind while you learn.

Pool Clarity's dosing calculations use muriatic acid (31.45%) as the default because it's the most common and cost-effective option. If you use dry acid, you'll need about 34 ounces of sodium bisulfate to get the same effect as 20 ounces of muriatic acid.