Phoenix Pools: City Water Stealing Electrolyte Gains?

By Franklin Everett Shaw

November 9, 2025

The shimmering heat rises off the asphalt, blurring the edges of the strip malls. It’s another scorcher in Phoenix, and the only escape seems to be a dip in the pool. But before you cannonball in, consider this: that refreshing water might be subtly leaching vital electrolytes from your body, leaving you feeling drained and depleted. The unique mineral composition of Phoenix’s water supply, while safe for consumption, can throw off your body’s delicate balance, especially during prolonged swimming.

Phoenix’s municipal water, sourced from a combination of the Salt River Project (SRP) and the Central Arizona Project (CAP), is known for its relatively high mineral content. This isn’t necessarily a bad thing for drinking water, but it presents a unique challenge for swimmers. The water is treated to meet federal and state standards, but the naturally occurring minerals remain.

Specifically, Phoenix water tends to be higher in calcium and magnesium compared to other regions. While these are essential minerals, an imbalance can occur when you’re submerged for extended periods. The process of osmosis means that water, including pool water, will move across cell membranes to try and equalize the concentration of solutes (like electrolytes) on either side.

This means that if the pool water has a lower concentration of electrolytes than your body fluids (which is often the case, even with minerals present), water will move into your body, diluting your electrolyte levels. This effect is amplified in Phoenix pools due to the already mineral-rich water pulling electrolytes out of the swimmer’s body.

So, what can you do about it? The key is proactive hydration and electrolyte replenishment, tailored to the specific challenges of swimming in Phoenix water.

First, test your pool water. Don’t rely on assumptions. You can purchase inexpensive pool testing kits at any local pool supply store, like Leslie’s Pool Supplies (multiple locations throughout Phoenix) or Pinch A Penny Pool Patio Spa (also widely available). These kits typically measure pH, alkalinity, chlorine, and calcium hardness. While they don’t provide a comprehensive mineral analysis, the calcium hardness reading is a good indicator of the overall mineral load. Aim for a calcium hardness level within the recommended range for your pool type (usually 200-400 ppm). If it’s significantly higher, consider partially draining and refilling your pool with fresh water.

If you want a more detailed analysis, consider sending a sample to a certified laboratory. The Arizona Department of Health Services provides a list of certified labs that can perform water quality testing. This will give you a precise breakdown of the mineral content, allowing for more targeted electrolyte supplementation.

Next, adjust your pre-swim hydration strategy. Don’t just drink water. Plain water can further dilute your electrolyte levels. Instead, opt for electrolyte-rich beverages. Look for sports drinks that contain sodium, potassium, magnesium, and calcium. Nuun tablets are a good option, as they are low in sugar and provide a balanced electrolyte profile. Consider adding a pinch of sea salt to your water bottle for an extra boost of sodium.

A good pre-swim hydration plan might look like this:

• One hour before swimming: 16-20 ounces of an electrolyte drink (e.g., Nuun, Gatorade Zero).
• 30 minutes before swimming: 8-12 ounces of water with a pinch of sea salt.

During your swim, especially if it’s longer than 30 minutes, continue to hydrate with electrolyte-rich beverages. Keep a water bottle poolside and take regular sips.

Post-swim recovery is crucial. This is where you replenish the electrolytes lost during your swim. Don’t wait until you feel thirsty or fatigued. Immediately after swimming, consume a recovery drink that contains electrolytes and carbohydrates. Chocolate milk is a surprisingly effective recovery drink, providing a good balance of electrolytes, carbohydrates, and protein. Alternatively, you can use a dedicated recovery supplement like Endurox R4.

Consider these specific electrolyte recommendations, tailored to Phoenix water:

• Sodium: Crucial for fluid balance and nerve function. Aim for 500-700mg post-swim.
• Potassium: Important for muscle function and blood pressure regulation. Aim for 200-400mg post-swim.
• Magnesium: Often depleted in Phoenix swimmers due to the high calcium levels in the water. Aim for 50-100mg post-swim. Consider a magnesium supplement if you experience muscle cramps or fatigue.
• Calcium: While Phoenix water is high in calcium, it’s still important to ensure adequate intake, especially for bone health. Aim for 200-300mg post-swim, but don’t overdo it.

Be aware of the signs of electrolyte imbalance. These can include muscle cramps, fatigue, headache, nausea, and dizziness. If you experience any of these symptoms, stop swimming and replenish your electrolytes immediately.

Common pitfalls to avoid:

• Over-reliance on plain water: As mentioned earlier, plain water can dilute your electrolyte levels.
• Ignoring individual needs: Everyone’s electrolyte needs are different. Factors like sweat rate, intensity of exercise, and individual metabolism play a role. Experiment to find what works best for you.
• Assuming all sports drinks are created equal: Many sports drinks are high in sugar and low in electrolytes. Read the labels carefully and choose options that provide a balanced electrolyte profile.
• Neglecting post-swim recovery: Replenishing electrolytes after swimming is just as important as hydrating before and during.

Real-world scenario: Imagine you’re training for the Ironman Arizona, which includes a 2.4-mile swim in Tempe Town Lake (which is filled with treated Salt River water, similar to Phoenix municipal water). You’re putting in long hours in the pool, and you start to experience muscle cramps during your workouts. This is a classic sign of electrolyte imbalance. By testing your pool water, adjusting your pre- and post-swim hydration strategies, and supplementing with magnesium, you can mitigate these cramps and improve your performance.

Swimming in Phoenix pools offers a welcome respite from the desert heat, but it’s important to be aware of the potential impact on your electrolyte balance. By following these guidelines, you can stay hydrated, healthy, and performing at your best. Don’t let the water drain you – empower yourself with knowledge and a proactive hydration strategy. Remember to consult with a healthcare professional or registered dietitian for personalized advice.