How to Lower Pool Alkalinity: Step-by-Step Guide

Tools & Supplies Needed

Find on Amazon: Taylor K-2006 Pool Test Kit , Muriatic Acid for Pools , Sodium Bisulfate Dry Acid , Chemical Safety Goggles

Quick Answer

High alkalinity can be lowered using muriatic acid (hydrochloric acid) or sodium bisulfate (dry acid). The most effective method is adding muriatic acid to the deep end of your pool with circulation running, then allowing it to distribute for several hours before retesting.

Step-by-Step Process to Lower Alkalinity

1. Test your current alkalinity levels using a reliable test kit like the Taylor K-2006 or comparable digital tester. Record both alkalinity and pH readings as you'll need to monitor both throughout this process.
2. Calculate the required acid amount. For muriatic acid: use approximately 1.3 lbs (about 20 fl oz) per 10,000 gallons to reduce alkalinity by 10 ppm. For sodium bisulfate: use about 2 lbs per 10,000 gallons for the same reduction.
3. Prepare your safety equipment. Wear safety goggles, chemical-resistant gloves, and long sleeves. Ensure you're wearing closed-toe shoes and have a water source nearby for emergency rinsing.
4. Turn on your pool pump and ensure good circulation. This helps distribute the acid evenly and prevents localized damage to pool surfaces.
5. Add acid to the deepest part of your pool. For muriatic acid, pour slowly in a sweeping motion underwater (never pour into a skimmer). For dry acid, pre-dissolve it in a bucket of pool water, then pour the solution into the deep end.
6. Allow circulation for 4-6 hours without swimming. Keep the pump running to ensure complete mixing throughout the pool system.
7. Retest alkalinity and pH. The acid will lower both values, so you'll likely need to raise pH back to the ideal range of 7.4-7.6 using sodium carbonate (soda ash).
8. Adjust pH if necessary. Add soda ash if pH dropped below 7.2. Use about 6 oz per 10,000 gallons to raise pH by 0.2 units.
9. Wait 24 hours and retest to confirm your alkalinity is in the target range of 80-120 ppm for chlorine pools or 60-80 ppm for salt water generators.
10. Repeat if needed but never add more than the calculated amount at once. It's better to make gradual adjustments over several days.

Understanding the Alkalinity-pH Relationship

Total alkalinity acts as a pH buffer, preventing rapid pH swings in your pool. When alkalinity is too high (above 120-150 ppm), it makes pH difficult to adjust and can lead to cloudy water, scaling on equipment, and reduced chlorine effectiveness.

The challenge with lowering alkalinity is that acid affects both alkalinity and pH simultaneously. This is why the process requires patience and multiple adjustments. The key is to lower alkalinity first, then fine-tune pH afterward.

Choosing Between Muriatic Acid and Dry Acid

Muriatic acid is more cost-effective and faster-acting but requires careful handling due to its liquid form and strong fumes. It's the preferred choice for larger alkalinity reductions.

Sodium bisulfate (dry acid) is safer to handle and store, making it ideal for pool owners uncomfortable with liquid acids. It dissolves completely and won't affect calcium hardness, but it's more expensive per treatment.

Advanced Technique: Acid Demand Testing

For precise alkalinity reduction, perform an acid demand test using your Taylor test kit. This helps determine exactly how much acid your specific pool water requires, accounting for variables like calcium hardness and current pH levels.

Safety Precautions and Important Warnings

Never mix chemicals or add them simultaneously. Always add acid to water, never water to acid, to prevent dangerous reactions and splashing.

Store chemicals properly in a cool, dry area away from other pool chemicals. Muriatic acid should be stored in its original container with a tight-fitting lid.

Ventilation matters when using muriatic acid, especially in enclosed pool areas. The fumes can be irritating to eyes and respiratory system.

Common Mistakes to Avoid

• Adding too much acid at once, causing pH to crash below 7.0
• Not running circulation during treatment, leading to localized etching
• Swimming too soon after treatment before proper mixing occurs
• Ignoring pH levels while focusing only on alkalinity
• Using stabilized chlorine shock instead of proper acid for alkalinity reduction

When to Seek Professional Help

If your alkalinity consistently runs high despite treatment, or if you're uncomfortable handling acids, consult a professional pool service. Persistent high alkalinity might indicate issues with your water source or pool equipment that require expert diagnosis.