💧 Why & How to Partially Drain Your Pool
A Premier Pool & Spa Guide to Smarter Water Management
Keeping your pool clean isn’t just about chemicals and cleaning—it’s also about knowing when to replace part of your water. Partial draining is a smart maintenance strategy that helps reset your water chemistry and restore balance when things get out of control.
🧪 Why You Might Need to Partially Drain Your Pool
1. High Total Dissolved Solids (TDS)
Over time, minerals and organic matter build up, increasing TDS. If levels exceed 1500 ppm above your source water, it can cause:
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Cloudy water
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Reduced sanitizer effectiveness
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Difficulty balancing pH
Partial draining helps bring those levels back down.
2. Excess Cyanuric Acid (CYA)
CYA stabilizes chlorine—but too much of it "locks" your chlorine, making it ineffective. The only fix? Drain and dilute. If your CYA is too high, it’s time to replace some water.
3. High Phosphates
Phosphates feed algae. If your levels are over 4000 ppb, a partial drain before treatment helps reduce the organic load for better algae prevention.
4. Unstable Chlorine Levels
If you can’t keep chlorine in the pool, nitrates may be the problem. Since nitrates can’t be removed chemically, dilution is the best solution.
⚠️ Why You Shouldn’t Fully Drain Your Pool
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Vinyl Pools: Liners can float or wrinkle and may not reseat properly.
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Concrete or Fiberglass Pools: Risk of "floating" or structural damage if groundwater pressure is high.
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Overall Risk: Draining completely can weaken your pool’s structure and void warranties.
💡 Stick with a partial drain unless guided otherwise by a pro.
✅ What to Do Before You Drain
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Check Local Codes
Many cities restrict pool water disposal. Never drain into storm sewers without verifying. -
Open Your Auto Cover
Keep it fully open during the process to avoid damage. -
Consider Flocculants or Enzyme Treatments
Use flocculants or first aid products to drop debris to the pool floor before draining—makes the process more effective.
🛠 How to Partially Drain Your Pool
🔹 Option 1: Submersible Pump (Most Controlled)
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Place an auto cover pump on the second step to prevent over-draining
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Simultaneously run a hose into the skimmer to refill
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Turn off the skimmers as water drops to avoid pulling air
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Adjust pump height as needed
🔹 Option 2: Drain via Main Drain (Best for High CYA)
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Roll out a backwash hose to an approved drainage area
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Turn off the pump and close skimmer valves
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Leave the main drain open
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Set multiport valve to "Waste"
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Turn pump back on
✅ Add fresh water with a hose while draining for better water turnover
✅ Stop before return lines are exposed—leave at least 12" in the shallow end -
Reset valve to “Filter” and restart pump
🔹 Option 3: Vacuum to Waste (Best for Dirty Water After Flocculants)
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Only possible with a waste line (Sand or DE filters, sometimes Cartridge)
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Use this after flocculants to vacuum settled debris directly out
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Safer method—requires you to monitor water level constantly
📖 Read our guide to vacuuming to waste
🚿 Refilling Your Pool: Do It Right
1. Use a Hose Filter
If your source water contains metals or sediment, use the Pleatco Pre-Filter to prevent stains or scaling.
2. Start Refilling Early
Begin refilling as you drain to maintain pool weight and balance the water exchange.
💡 Make sure refill water is entering in a different location than the drain to avoid cycling the same water.
💬 Need Help?
Draining and refilling the right way makes a big difference in water quality and equipment performance. If you're unsure where to start:
📅 Book a service appointment
📩 Contact us for expert advice
Premier Pool & Spa – Safe water. Smarter care. Local support you can trust.
Proudly independent—not affiliated with any national franchise.
