Using Dry Acid in Your Swimming Pool to Lower the pH

September 11, 2020

Dry acid is one pool chemical not talked about much. I think mainly because the use of muriatic acid to lower the pH in a pool is so widely entrenched in the minds of pool pros and homeowners that Dry Acid is often overlooked. It is also a bit more expensive to use over muriatic acid, although as the price for muriatic acid continues to rise dry acid is becoming more and more popular because of the safety and storage benefits.

Although there are a lot of positives about dry acid there was one study done that highlights some potential negative effects of dry acid. But according to my source to achieve this level you would need to add 75 lbs. of dry acid and bring the level in a pool to 300 ppm. So the study may not be all it is cut out to be. Here it is for you so you can see both sides of the product: https://www.pwtag.org/sulphate-attack-february-2011/

You will see dry acid sold as pH Reducer, pH down or of course labeled as Dry Acid. Just look for the active ingredient sodium bisulfate on the label.

Safer to Use: Sodium Bisulfate is a dry, granular form of acid. This makes it safer for handling, and it is far less corrosive in a pump room or other space as it is not a strong oxidizer like muriatic acid. It Sodium bisulfate needs to be stored in a dry place, without moisture getting into the container. Sodium bisulfate must be pre-dissolved before being added to the pool, just like any other dry chemical. But if you spill it or get any of it on the pool deck it won’t burn your skin or stain your deck.

Benefits:

Does not burn your skin

Longer shelf life

Easy to store

No toxic fumes

It won’t rust everything around your house or equipment room

Strong as muriatic acid with proper dosage

Easy to use

Adjusting the pH in your pool is critical for proper water balance and to make sure that the water in your pool is not scale forming nor is it being corrosive. The pH is one important element in this. Note also that when you adjust the pH you are also adjusting the Alkalinity. And that the higher the Alkalinity is over the baseline of 80-120 ppm the more dry acid you will need to lower the pH. This is because Alkalinity is a buffer in the water and will slow down the affect of any acid you add if the water is very alkaline.

Dry acid is a bit more expensive than muriatic acid if you are comparing pound for pound which is a bit more difficult because one is in a dry form and the other in a liquid form. But if you measure the dosage of the dry acid correctly it is just as strong as 31.45% muriatic acid. I think for the safety and storage benefits dry acid is hands down better for homeowner use as well as some service pro use. I like to carry a 50 lbs. bucket in the back of my truck and find it very handy as it gives me more space to carry my other chemicals and equipment. It is also good for adding acid to those service accounts were pets are present or the homeowner is next to the pool. The last thing you want to do is pour in a quart of muriatic acid and have them overcome by fumes.

It is best to pre-dissolve the dry acid in a bucket and then once it is dissolved to pour it around the perimeter of the deep end with the pool on and running for at least 3 hours minimum. You can toss it directly in but it is not advised and it only takes 3-5 minutes to dissolve it in a bucket. You will also need a scale to weigh the product to get the exact dosage and I recommend using an online app to get the right dosage amount. Remember that the Alkalinity is a factor so if it is above 120 ppm you will need more of the dry acid to move the pH down.

A good online tool is the https://www.poolcalculator.com/

There are many very good reasons to switch to dry acid and of course the fact that it is safer to use is a big one.

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