Tips for Using Well Water in Your Pool | Prevent Stains & Scale
By Sonoma Pool Service – Sonoma County’s Pool Water Experts

Thinking about using well water to fill or top off your swimming pool? It’s a common approach in rural areas like Sonoma County. But well water often carries high levels of calcium, iron, magnesium, and copper. While not harmful to health, these minerals can cause staining, scale buildup, or cloudy water if not properly managed.
Managing Calcium in Well Water for Your Pool
Some calcium is essential to maintain water balance and protect plaster surfaces. But excessive calcium—often present in well water—can lead to:
- White scale deposits on tile, filters, and heating elements
- Cloudy or hazy pool water
What to do:
- Monitor and balance your water’s pH and alkalinity
- Use scale inhibitors when calcium hardness is high
- Consider partial pool fills to control hardness over time
- For ongoing issues, reverse osmosis filtration can reduce minerals without draining the pool
Controlling Magnesium from Well Water in Your Pool
Magnesium is usually less problematic on its own, but combined with calcium, it contributes to total hardness and scaling risks.
Our advice: Track your total hardness levels and adjust water chemistry as needed. Enzyme-based clarifiers can also help improve clarity if the water looks dull or cloudy.
Dealing with Iron in Well Water in Your Pool
Iron is one of the most common minerals in well water and the top cause of reddish or brown stains on steps, tile, and pool finishes. When iron oxidizes with chlorine, it causes discoloration and water cloudiness.
Solution:
- Add metal sequestrants to suspend iron and prevent oxidation
- Maintain sequestrant levels after every new water addition
- Address existing stains with a professional iron treatment plan
Managing Copper in Well Water for Your Pool
Often found in well water or introduced via algaecides and copper plumbing, copper causes:
- Blue-green stains on pool surfaces
- Tinted pool water or even green-tinted hair
Prevention tips: Use metal control agents and test copper levels routinely. Treat discoloration early before it causes permanent surface damage.
Smart Ways to Use Well Water in Your Pool Safely
If your well water has high mineral content, you can still use it safely with a few smart precautions:
- Fill your pool gradually and treat the water during the process
- If available, mix well water with softened or filtered water
- Invest in reverse osmosis systems for long-term control
- Stick to a strict maintenance plan to control chemistry and mineral buildup
Final Thoughts on Using Well Water in Your Pool
Well water can be a practical and cost-effective way to maintain your pool, but it requires a proactive approach. With consistent water testing and the right treatments, you can avoid costly damage, unsightly stains, and long-term equipment wear.
Need help managing minerals in your pool?
At Sonoma Pool Service, we help homeowners treat and manage well water with custom care plans. From initial fill to long-term maintenance, we know how to protect your investment.
📞 Call us today at (707) 933-9244 or visit SonomaPoolService.com to get started.