Yes, pool pH naturally tends to rise over time due to chlorine sanitization, aeration from equipment, and swimmer activity. Most pools require regular pH adjustment downward using muriatic acid to maintain the ideal 7.4-7.6 range.
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Pool pH naturally increases over time in most pools. This upward drift happens because of chlorine sanitization, water aeration from pumps and returns, and bather activity. The vast majority of pool owners need to regularly add muriatic acid or sodium bisulfate to lower pH back to the ideal 7.4-7.6 range.
The primary driver of rising pH is your chlorine sanitizer. When liquid chlorine (sodium hypochlorite) dissolves in water, it creates hypochlorous acid and raises pH. Even though the hypochlorous acid formation should theoretically balance this effect, the ongoing chlorine demand from killing bacteria and breaking down organic matter creates a net pH increase over time.
Salt water chlorine generators (SWG) also drive pH up significantly. The electrolytic process that converts salt to chlorine inherently raises pH, which is why SWG pools require more frequent pH adjustment than traditionally chlorinated pools.
Pool equipment naturally aerates water, which drives off dissolved carbon dioxide. When CO2 leaves the water, it reduces carbonic acid levels, causing pH to rise. This happens through:
Swimmers contribute to pH rise through perspiration, cosmetics, and body oils. While these contaminants initially consume chlorine (which can temporarily lower pH), the overall oxidation process and chlorine replenishment typically results in net pH increase.
Test pH levels 2-3 times per week using a reliable test kit. The Taylor K-2006C drop test kit provides accurate readings and is preferred over test strips for precision. Test in the morning before adding chemicals and after the pump has run overnight for proper water circulation.
Muriatic acid (hydrochloric acid) is the most effective pH reducer for most pools. For every 0.2 pH units you need to drop in a 20,000-gallon pool, add approximately 1 quart of muriatic acid. Always add acid to the deep end with the pump running, never pour water onto acid.
Safety Warning: Wear protective eyewear and gloves when handling muriatic acid. Store in original container away from other pool chemicals.
Dry acid (sodium bisulfate) works more slowly but is easier to handle. Use about 2 pounds per 20,000 gallons to lower pH by 0.2 units. Pre-dissolve in a bucket of pool water before adding to avoid temporary cloudiness.
Total Alkalinity (TA) acts as pH's buffer system. If your pH constantly spikes despite regular acid additions, your TA is likely too high. Target TA levels of 60-80 ppm for salt water pools and 80-120 ppm for traditionally chlorinated pools.
High TA makes pH rise faster and resist downward adjustment. Use muriatic acid to lower both pH and TA simultaneously, but expect this process to take several days with multiple small additions rather than one large dose.
Occasionally, pools experience falling pH instead of the typical upward trend. This usually indicates:
In these cases, use sodium carbonate (soda ash) to raise pH or sodium bicarbonate to raise both pH and total alkalinity.
Establish a routine testing schedule checking pH every 2-3 days during swimming season. Keep muriatic acid on hand as most pools require pH adjustment 1-2 times per week. Record your readings to identify patterns - pools with salt water generators, heavy bather loads, or extensive water features typically need more frequent pH correction.
Retest pH levels 4-6 hours after adding acid to ensure proper distribution and avoid over-correction. Maintain consistent free chlorine levels according to your CYA level using the FC/CYA chart, as proper sanitizer balance helps stabilize overall water chemistry.
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