How To Drain A Swimming Pool With A Pump: A Step-by-Step Professional Guide

Draining a swimming pool with a pump requires choosing between a submersible utility pump (recommended) or the pool's primary filtration system to safely evacuate water without structural damage. Success hinges on monitoring local runoff regulations, managing hydrostatic pressure to prevent pool lifting, and executing a controlled drawdown of no more than 1 inch per hour. By following precise electrical and hydraulic protocols, you can empty your pool safely for liner replacements, structural repairs, or seasonal winterization.

Pre-Draining Assessment and Equipment Checklist

Before initiating a pool drawdown, you must determine why you are draining the pool and verify that the local water table is low enough to prevent catastrophic structural failure. Emptying a swimming pool removes the ballast weight of the water, which can reach upwards of 160,000 pounds for a standard 20,000-gallon pool. Without this weight, hydrostatic pressure from underground water tables can push upward on the pool shell, causing concrete pools to pop out of the ground, fiberglass pools to buckle, or vinyl liners to float and wrinkle permanently.

To prevent these disasters, never drain a pool after heavy rainfall, and always locate the hydrostatic relief valve on your pool floor before starting. Additionally, you must review municipal guidelines regarding wastewater discharge, as many cities restrict discharging chlorinated or salt-heavy pool water directly into storm drains.

Essential Equipment and Materials

• Submersible Utility Pump: Rated at a minimum of 1/4 Horsepower (HP), though 1/2 HP to 1 HP is preferred for faster flow rates and higher head pressure. Do not use your pool's primary filtration pump to empty the pool completely, as it risks sucking air and burning out the motor once the water level falls below the skimmer.
• Heavy-Duty Discharge Hose: A 1.5-inch or 2-inch lay-flat hose, long enough to reach from the deepest point of your pool to the designated municipal cleanout drain or legal discharge zone.
• Hose Clamps: Stainless steel worm-gear clamps to secure the hose to the pump discharge port.
• GFCI Extension Cord: An outdoor-rated, heavy-gauge extension cord connected strictly to a Ground Fault Circuit Interrupter (GFCI) outlet.
• Dechlorinating Agent: Sodium thiosulfate or a similar chemical neutralizer to lower free chlorine levels to 0.1 ppm or lower before discharge.
• Personal Protective Equipment (PPE): Rubber boots, safety glasses, and heavy-duty gloves.

Prerequisite Knowledge & Project Benchmarks

• Target Free Chlorine: Under 0.1 ppm.
• Target pH Level: Between 6.5 and 8.5.
• Estimated Budget: $150 to $300 for pump rental or purchase and safety accessories.
• Estimated Duration: 8 to 16 hours, depending on pool volume (gallons) and pump flow rate (gallons per hour).

Step-by-Step Pool Draining Protocol Using a Submersible Pump

Follow this precise sequence of steps to safely evacuate pool water, protect your equipment from damage, and prevent structural shifting of your pool shell.

Step 1: Dechlorinate and Balance the Pool Water

Do not discharge chemically active pool water into public drainage systems or onto your lawn. At least 48 hours before you plan to drain the pool, stop adding chlorine, algaecides, or other chemicals. Run a complete water chemistry panel to ensure the free chlorine level has dropped to 0 ppm or near-zero levels. If the pool is green or highly chlorinated and must be drained immediately, apply a chemical dechlorinating agent like sodium thiosulfate according to package instructions to neutralize active sanitizers.

Step 2: Shut Down All Pool Systems at the Main Breaker

Go to your pool's main electrical subpanel and switch off the circuit breakers for all active pool equipment. This includes the primary circulation pump, pool heater, salt chlorine generator, automated chemical feeders, and pool lights.

Warning: If the main pool pump turns on via an automated timer while the pool is empty or partially empty, it will pull air into the system, lose prime, and rapidly overheat. This can melt the pump's internal plastic fittings, ruin the shaft seal, and burn out the motor windings, resulting in an expensive replacement.

Step 3: Run the Discharge Hose to a Legal Drainage Zone

Unroll your lay-flat discharge hose from the pool edge to your designated drainage area. The ideal location is a sanitary sewer cleanout port on your property, which routes the water directly to a wastewater treatment plant. If a cleanout is unavailable, and local laws permit, you may route the hose to a street curb or storm drain, provided the water is fully dechlorinated.

Ensure the hose runs straight with no kinks, sharp turns, or elevated loops. High head heights (pumping uphill) drastically reduce a pump's gallons-per-minute (GPM) output.

Step 4: Position and Secure the Submersible Pump

Attach the discharge hose securely to the submersible pump's outlet port using a stainless steel worm-gear clamp. Tighten the clamp with a flathead screwdriver or nut driver until the hose cannot be pulled off by hand. Lower the submersible pump slowly into the deepest part of your pool using a dedicated nylon retrieval rope tied to the pump's handle.

Pro-Tip: Never lower, lift, or suspend a submersible pump by its electrical power cord. This places severe strain on the waterproof seal where the cord enters the motor housing, which can cause water intrusion, short-circuiting, and permanent pump failure.

Ensure the pump sits flat on the pool floor. If your pool has a vinyl liner, place a smooth, flat plastic pad or a rubber utility mat directly underneath the pump. This prevents the hard plastic or metal base of the pump from vibrating against the liner, which can wear holes into or tear the vinyl during hours of operation.

Step 5: Establish the Electrical Connection and Initiate Pumping

Route the pump’s heavy-duty electrical cord to a dry area away from pool water splashing. Plug the cord into a GFCI-protected outlet. If you must use an extension cord, verify that it is rated for outdoor use, has a three-prong grounded plug, and is rated for the amperage draw of your specific pump (typically 12 to 14 gauge for runs up to 50 feet).

Once plugged in, the pump should immediately begin humming and discharging water. Walk to the end of your discharge hose to confirm that water is flowing freely and not causing soil erosion, flooding your home’s foundation, or spilling into a neighbor's yard.

Step 6: Monitor Water Level and Hydrostatic Pressure

Check the draining progress every hour. Calculate the drawdown rate by measuring from a coping tile to the water line; do not exceed a rate of 1 inch of vertical drop per hour.

If you are draining a concrete, gunite, or plaster pool, locate the hydrostatic relief valve on the pool floor once the water level drops low enough. Unscrew the valve plug using a specialized plug wrench or channel locks. Opening this valve allows any high-pressure groundwater underneath the pool to seep up into the pool shell safely, balancing the external and internal pressures and preventing the pool from shifting or popping out of the ground.

If you are draining a vinyl liner pool, watch the liner closely. If you notice the liner wrinkling, shifting, or lifting away from the concrete backing walls, stop pumping immediately. This indicates that groundwater levels are too high, and the lack of water weight is allowing the liner to float.

Step 7: Clear Residual Water and Debris

Submersible utility pumps rely on a built-in intake screen on the bottom of the unit to filter out large debris. As the water level reaches the final 2 inches, leaves and small twigs will gravitate toward the pump, potentially clogging this screen. Keep a pool brush handy to sweep debris away from the pump intake.

Once the water level falls below the pump’s minimum suction depth (usually between 1/4 inch and 1/2 inch), the pump will begin sucking air and spitting water. Unplug the pump immediately to prevent the internal motor seals from overheating. Use a heavy-duty wet/dry shop vacuum to siphon out the remaining shallow puddles of water from the deep end sump.

Pump Performance and Water Drawdown Benchmarks

Selecting the correct pump type and understanding its output characteristics under real-world conditions is vital for planning your drainage timeframe. The table below compares common pump types used for draining swimming pools.

Common Draining Failures and Field Remedies

Draining a pool rarely goes perfectly without intervention. If you run into issues, utilize these common failure scenarios and technical fixes to get back on track.

The Submersible Pump Runs but Stops Discharging Water

• Root Cause: The pump has experienced an airlock. This occurs when an air bubble gets trapped inside the impeller housing, preventing the pump from building enough pressure to push water up and out of the discharge hose.
• Actionable Fix: Unplug the pump from the electrical outlet. Tilt the pump to a 45-degree angle while it is fully submerged in the water. This allows the trapped air bubble to escape from the bottom intake or the weep hole. Gently shake the pump, place it flat on the pool floor, and plug it back in.

The Pump Shuts Off Prematurely and Feels Extremely Hot

• Root Cause: Thermal overload protection has tripped. Submersible pumps rely on the surrounding pool water to cool their internal motors. If the pump runs dry, or if the impeller is jammed by debris, the motor will rapidly overheat and shut down automatically to prevent permanent burnout.
• Actionable Fix: Unplug the pump immediately and pull it out of the pool. Turn the pump upside down and inspect the intake screen. Remove any leaves, hair, or small stones clogging the impeller. Let the pump cool down completely in a shaded area for at least 30 to 45 minutes. Once cooled, the thermal switch will reset, allowing you to submerge the pump and restart.

The Vinyl Pool Liner is Wrinkling and Separating from the Wall

• Root Cause: Groundwater pressure is pushing upward against the outside of the vinyl liner because the weight of the pool water inside has been removed too quickly.
• Actionable Fix: Stop the pump immediately. Do not drain any more water. Begin refilling the pool with fresh water from a garden hose or water truck. The weight of the rising water is necessary to push the vinyl liner back flat against the structural walls and floor. If wrinkles persist, you may need to hire a professional pool technician to use a liner vacuum to reset the liner.

The Discharge Hose Keeps Kinking and Stopping the Flow

• Root Cause: The discharge hose has low wall-thickness or is routed around tight, structural corners, causing it to collapse under backpressure or drop in water velocity.
• Actionable Fix: Turn off the pump to relieve hose pressure. Straighten out the lay-flat hose, eliminating any twists or sharp 90-degree turns. If routing over a retaining wall or pool coping, place a thick towel or a curved piece of PVC pipe under the hose to prevent it from pinching shut over the hard edge.

Frequently Asked Questions

Can I use my pool's main filter pump to drain the entire pool?

No, you should not use your pool's main filter pump to drain the pool completely. While you can use the multiport valve's "Waste" setting to lower the water level, the main pump will lose prime and draw in air once the water level drops below the bottom of the skimmer opening. Running a pool pump dry will quickly destroy the shaft seal, melt the plastic pump basket, and burn out the motor. Only use a submersible utility pump to safely drain the water below the skimmer level.

How long does it take to drain a swimming pool with a submersible pump?

A standard 20,000-gallon pool will take between 6 and 10 hours to drain using a standard 1/2 HP submersible utility pump discharging at an average rate of 2,500 gallons per hour. The exact time depends heavily on the horsepower of your pump, the length and diameter of your discharge hose, and the elevation change between the bottom of the pool and the discharge point.

Is it safe to leave a pool empty for a long period?

No, it is highly risky to leave a swimming pool empty for more than 24 to 48 hours. Without water weight acting as a stabilizing ballast, concrete pools can pop out of the ground due to hydrostatic pressure, vinyl liners will shrink and dry out in the sun, and fiberglass shells can shift or buckle. Always plan your repairs or liner replacements to occur immediately after draining, and refill the pool as soon as the work is complete.

How do I prevent hydrostatic pressure from destroying my pool when draining?

To prevent hydrostatic pressure damage, never drain your pool during or immediately after heavy rainfall when the ground is highly saturated. Before draining, locate the hydrostatic relief valve on the pool floor. Once the water level is low enough, open this valve to allow underground water to flow into the pool, neutralizing the pressure differential. If you suspect a high water table, consult a professional pool builder before emptying the shell.

Where is the best place to discharge the drained pool water?

The safest and most environmentally responsible place to discharge pool water is your home’s sanitary sewer cleanout port, typically located near the foundation or in the yard. This routes the chlorinated or salty water directly to your municipal water treatment facility. Avoid discharging large volumes of water onto lawns or gardens, as chlorine and salt can kill vegetation and oversaturate the soil around your home's foundation.

Keep Your Pool Running Safely and Efficiently

Draining a pool is a complex maintenance task that must be executed with extreme care to prevent structural damage. If you feel uncomfortable managing the hydrostatic relief valves or electrical safety protocols, contact a certified pool technician in your area for professional assistance.