How to Drain a Pool: A Step-by-Step Guide That Won’t Destroy Your Yard (or Your Wallet)
Every pool owner eventually faces it — that moment when you realize your water is beyond saving. Maybe your TDS levels hit 3,000+ ppm, or cyanuric acid climbed so high that chlorine stopped working. Perhaps you’re staring at a swamp-green disaster after a long vacation. Whatever brought you here, knowing how to drain a pool safely is essential knowledge that can save you thousands in repairs.
Here’s the thing most pool guides won’t tell you: draining a pool incorrectly can crack your shell, flood your neighbor’s yard, or even make your entire pool pop out of the ground. Yes, really. I’ve seen it happen.
But don’t panic. This guide walks you through the entire process, from deciding whether you actually need to drain to refilling and rebalancing. Let’s get your pool back to crystal clear.
When Should You Actually Drain Your Pool?
Before you rent that submersible pump, ask yourself: do you really need to drain?
Full drains are a last resort. Most water problems can be solved with partial drains, heavy shocking, or patience. But sometimes, there’s no way around it.
Valid Reasons to Drain
- Cyanuric acid above 100 ppm — Dilution is the only solution
- Total dissolved solids exceeding 2,500 ppm — Your water is mineral soup
- Major structural repairs — Resurfacing, crack repair, or tile work
- Severe algae infestation — When shocking fails three times in a row
- Complete water replacement — Required every 5-7 years for most pools
When Partial Draining Works Better
If your CYA sits around 80-90 ppm, drain 25-30% and refill. That dilutes the problem without the risks of a full drain. Same goes for slightly elevated TDS or minor calcium issues.
Before You Start: Critical Safety Checks
Skip these steps and you might crack your pool shell or flood your basement. Seriously.
Check Your Pool Type
Fiberglass and vinyl liner pools should almost never be fully drained without professional supervision. The shells rely on water pressure to maintain their shape. An empty fiberglass pool can buckle, and vinyl liners shrink and crack when exposed to air and sun.
Concrete and gunite pools handle draining better, but they’re not invincible. Groundwater pressure can literally push an empty concrete pool out of the ground — a phenomenon called “pool pop.” It happens more often than you’d think.
Assess Groundwater Conditions
Here’s your pre-drain checklist:
1. Check recent rainfall — Wait 3-5 days after heavy rain
2. Look for a high water table — If your area floods easily, proceed with caution
3. Inspect for hydrostatic relief valves — Most in-ground pools have these at the deep end to relieve groundwater pressure
4. Check weather forecasts — Never drain before predicted storms
Know Your Local Laws
Many municipalities regulate where pool water goes. Some require you to discharge to the sewer system (not storm drains). Others mandate dechlorination before draining. Call your water department or check their website. Fines can hit $500-1,000 for improper discharge.
Equipment You’ll Need
Gathering everything beforehand saves multiple trips to the hardware store.
Essential Equipment
- Submersible pump — Rent one rated for at least 2,000-3,000 GPH (gallons per hour)
- Discharge hose — 50-100 feet, depending on where you’re sending the water
- Garden hose — For the final few inches and cleanup
- Hose clamps — Connections that slip off create flooding disasters
For most homeowners, I recommend the Wayne WaterBUG Submersible Pump. It handles pools up to 25,000 gallons efficiently and costs around $100 — cheaper than a one-day rental if you’ll ever need it again.
Optional But Helpful
- pH neutralizer or dechlorinator tablets
- Wet/dry shop vacuum for corners
- Soft-bristle brush for cleaning while empty
- Pressure washer (for concrete pools only)
Step-by-Step: How to Drain Your Pool
Ready? Here’s the actual process, broken down into manageable phases.
Step 1: Prepare the Water
Dechlorinate your water 3-5 days before draining. Stop adding chlorine and let sunlight break down what’s there. Target chlorine levels below 0.1 ppm before discharge. This protects plants, grass, and local waterways.
Add a dechlorinator if you’re in a hurry. Sodium thiosulfate works fast — typically 2 ounces per 1,000 gallons neutralizes 10 ppm of chlorine within hours.
Step 2: Turn Off Pool Equipment
Shut down everything:
- Pool pump
- Heater
- Salt chlorine generator
- Automatic cleaners
- Any timer-controlled equipment
Running your pump dry, even briefly, can burn out the motor. And that’s a $400-800 replacement.
Step 3: Position Your Submersible Pump
Drop the pump into the deep end. The lowest point drains first, which maintains weight distribution as water levels drop.
Connect your discharge hose securely (double-check those clamps) and run it to your approved discharge point. This might be:
- A sewer cleanout (preferred)
- The street gutter (check local laws)
- A drainage ditch
- Your lawn (only for small amounts of dechlorinated water)
Never discharge into storm drains. They flow directly to streams and lakes.
Step 4: Monitor the Drain Constantly
This isn’t a set-it-and-forget-it situation. Check the pump every 30-60 minutes.
A typical 20,000-gallon pool takes 8-14 hours to drain with a 2,500 GPH pump. Your actual time depends on pump efficiency, hose length, and elevation changes.
Watch for:
- Hose disconnections
- Pump clogs from debris
- Water backing up at the discharge point
- Signs of shell stress (cracking sounds, visible movement)
Step 5: Remove the Last Few Inches
Submersible pumps can’t grab the final 1-2 inches. Switch to a wet/dry vacuum or use a squeegee to push water toward the main drain.
For the absolute last puddles, the Shop-Vac 5989300 Wet/Dry Vacuum handles pool cleanup perfectly. It’s also useful for normal pool maintenance year-round.
Step 6: Work Fast While Empty
An empty pool is vulnerable. Groundwater pushes up constantly, and sun exposure damages surfaces. Aim to complete any repairs or cleaning within 24-48 hours maximum.
If you’re cleaning only, pressure wash concrete surfaces (never pressure wash fiberglass or vinyl), scrub stubborn stains with a pool surface cleaner, and inspect for cracks or damage while you have access.
Refilling Your Pool
Refilling seems simple, but a few details matter.
Calculate Refill Time
Most garden hoses deliver 400-600 gallons per hour. For a 20,000-gallon pool, that’s 33-50 hours of continuous running. A 20,000-gallon refill costs approximately $40-150 in water, depending on your local rates.
Consider renting a water delivery truck for faster refills — especially in drought areas where extended hose use draws attention.
Balance Chemistry Immediately
Fresh tap water isn’t balanced. Test and adjust within hours of filling:
1. Test pH — Tap water often runs 7.8-8.4 (too high)
2. Add calcium hardness increaser — Soft water damages plaster
3. Adjust alkalinity — Aim for 80-120 ppm first
4. Add stabilizer — Fresh water has zero cyanuric acid
5. Shock the pool — Always shock new fills
Your pump can restart once water reaches the skimmer opening — typically about halfway full for most pools.
Common Draining Mistakes to Avoid
Learn from others’ expensive errors:
- Draining during rain — Groundwater rises fast
- Leaving the pool empty overnight — Surface damage accelerates
- Forgetting hydrostatic plugs — These relief valves must stay open while empty
- Discharging chlorinated water onto lawns — You’ll have dead grass patches for months
- Not monitoring constantly — Pump failures and hose problems happen without warning
FAQ
How long does it take to drain a pool?
Most residential pools (15,000-25,000 gallons) drain in 8-14 hours using a 2,500 GPH submersible pump. Factors like hose length, elevation, and pump efficiency affect actual time. Plan for a full day of monitoring.
Can I drain my pool into the street?
It depends on local regulations. Some municipalities allow discharge to street gutters (which flow to sewers), while others prohibit it entirely. Always dechlorinate water first and check with your local water department before draining.
How much does it cost to drain and refill a pool?
Water costs range from $40-200 depending on pool size and local rates. Add $40-75 for pump rental if you don’t own one, plus $50-100 for chemicals to rebalance fresh water. Budget $150-350 total for a DIY drain and refill.
Will draining my pool damage it?
It can if done incorrectly. Fiberglass pools risk buckling, vinyl liners can shrink and crack, and concrete pools can “pop” from groundwater pressure. Always check conditions, drain during dry weather, and never leave a pool empty longer than necessary.
How often should I completely drain my pool?
Most pools need full draining every 5-7 years for water quality reasons. TDS and cyanuric acid accumulate over time and can only be reduced through dilution. However, well-maintained pools with regular partial water replacement may go longer between full drains.
Ready to rebalance after refilling? Head to Pool Chemical Calculator for exact chemical dosages for your pool size. Enter your test results and pool volume for instant recommendations.
Download the app:
- iPhone/iPad: https://itunes.apple.com/us/app/pool-chem-calculator/id1453351222
- Android: https://play.google.com/store/apps/details?id=com.poolchemicalcalculator.poolcalc
