While you can technically leave your pool covered all summer, it's not recommended as it creates anaerobic conditions that promote algae growth and equipment damage. If you must keep it covered, you'll need modified maintenance procedures.
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You can leave your pool covered for the summer, but it requires significant modifications to your maintenance routine and comes with substantial risks. Covered pools develop anaerobic conditions that promote algae growth, reduce sanitizer effectiveness, and can damage equipment. If you must keep your pool covered all summer, you'll need to increase chemical monitoring, run circulation equipment daily, and potentially remove the cover weekly for maintenance.
Leaving a pool covered continuously during summer creates several serious issues that go against fundamental pool chemistry principles. The primary concern is the development of anaerobic conditions - without sunlight and air exchange, beneficial aerobic bacteria die off while harmful anaerobic bacteria thrive.
When your pool is covered continuously, chlorine demand increases dramatically. The lack of UV light means your CYA (cyanuric acid) provides no benefit, while organic matter decomposes more rapidly in the dark, warm environment. You'll need to maintain FC (free chlorine) levels 2-3 times higher than normal - typically 8-12 ppm instead of the standard 3-5 ppm based on your CYA level.
pH levels also become unstable under covers. Without air exchange, CO2 builds up, driving pH down rapidly. You may need to test and adjust pH every 2-3 days instead of weekly.
Your circulation system faces increased strain when fighting the anaerobic conditions. Pool pumps and filters work harder to move water through the stagnant environment, while heaters can develop hot spots from poor circulation patterns under covers.
If circumstances require keeping your pool covered all summer, follow these intensive maintenance procedures:
Your filtration system will face much higher demand. Clean cartridge filters weekly instead of monthly, and backwash sand or DE filters every 3-4 days. Consider upgrading to a larger filter system if planning extended covered periods.
Standard dosing calculations change dramatically for covered pools. For a 20,000-gallon pool, you might need:
Safety Warning: Never add chemicals under a closed cover. Always remove or open covers completely, add chemicals, run circulation for 2 hours minimum, then re-cover.
Instead of 24/7 covering, consider using an automatic pool cover that opens daily for 4-6 hours during peak sun. This provides energy savings while maintaining aerobic conditions.
For extended absences (2-4 weeks), perform a modified winterizing procedure: shock to 20 ppm FC, add algaecide, reduce pH to 7.2, cover tightly, and have someone check weekly.
Full-time summer covering might be appropriate for:
Never assume covered pools need less maintenance. Many pool owners make the fatal error of reducing chemical additions and circulation time, leading to green, swampy conditions that require expensive SLAM procedures to correct.
Don't use regular pool shock products from retail stores - they often contain calcium hypochlorite that will drive up your calcium hardness. Stick with liquid chlorine (sodium hypochlorite) for covered pools.
Avoid using excessive algaecides as a substitute for proper chlorine levels. Algaecides supplement but never replace adequate FC levels.
Maintaining a covered pool all summer typically costs 200-300% more than normal operation due to increased chemical usage and equipment runtime. Factor in potential equipment replacement from increased wear when making your decision.
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