How To Pump Out Water From A Pool: A Complete Technical Guide To Safe Drainage

Safely draining a swimming pool requires a high-output submersible utility pump, a heavy-duty lay-flat discharge hose, and careful management of underground hydrostatic pressure. To prevent catastrophic structural shifting or liner damage, pool operators must route water to an approved municipal sewer cleanout while monitoring structural stability indicators throughout the drawdown process. This technical manual details the equipment specifications, safety protocols, and operational workflows required to execute a complete pool drain.

Pre-Drainage Preparation and Equipment Specifications

Before initiating a pool drawdown, you must establish an equipment baseline and assess environmental risks. Draining a pool exposes the structural shell to immense physical forces. In concrete, gunite, or fiberglass pools, hydrostatic pressure from high groundwater levels can literally lift the pool shell out of the ground—a catastrophic failure known as "pool popping." For vinyl-liner pools, removing water can cause the liner to shrink, crack, or pull away from the pool walls.

You must never drain a pool during or immediately after a heavy rainstorm when the surrounding soil is saturated. Always check the local water table level and review municipal ordinances regarding water discharge. Most municipal codes prohibit discharging chlorinated pool water, salty pool water, or water treated with copper algaecides directly into storm drains. Instead, they require discharging the water directly into your home's sanitary sewer cleanout, which routes the effluent to a wastewater treatment plant.

Required Equipment, Standards, and Benchmarks

• Submersible Utility Pump: 1/2 Horsepower (HP) to 1 HP continuous-duty submersible pump. Do not use your pool's primary filtration pump, as it will draw air and burn out once the water level drops below the skimmer line.
• Discharge Hose: 1.5-inch or 2-inch heavy-duty, reinforced PVC lay-flat hose. Smaller-diameter garden hoses (5/8-inch) restrict flow rates too severely, prolonging the drain time and increasing pump wear.
• Power Source: A dedicated 15-amp or 20-amp electrical outlet protected by a Ground Fault Circuit Interrupter (GFCI).
• Extension Cord: Heavy-duty, outdoor-rated, 12-gauge (AWG) minimum three-prong extension cord to prevent voltage drops.
• Hydrostatic Relief Plug Tool: A specialized T-bar wrench or long-reach channel locks to remove the hydrostatic valve at the bottom of the pool.
• Water Chemistry Test Kit: To verify that chlorine or bromine levels are at 0 parts per million (ppm) if local regulations allow storm drain discharge.
• Protective Barriers: Sandbags or hose clamps to secure the discharge end of the hose at the municipal cleanout to prevent whipping and localized flooding.
• Estimated Budget: $150 to $350 for purchasing high-quality equipment, or $50 to $70 per day for commercial equipment rental.
• Estimated Duration: 6 to 16 hours, depending on total pool volume and pump flow rate (e.g., a 20,000-gallon pool drained at 2,500 Gallons Per Hour will take approximately 8 hours).

Step-by-Step Pool Draining Execution

Follow this precise, step-by-step workflow to safely pump out your pool water without damaging the structural shell, lining, or electrical systems.

Step 1: Dechlorinate and Neutralize the Water

If you plan to discharge the water anywhere other than a sanitary sewer cleanout, you must render the water chemically inert. Run a full chemical analysis of the pool water using a photometer or liquid drop test kit. The chlorine or bromine concentration must read 0.0 ppm. The pH must sit within a neutral range of 7.2 to 7.8.

To neutralize chlorine rapidly, add sodium thiosulfate or sodium sulfite to the water according to the manufacturer's dosage instructions. Circulate the pool water for at least 24 hours after chemical application, and re-test to verify that no active sanitizer remains.

Step 2: Shut Down All Pool Equipment Power

Before lowering any equipment or altering valves, go to your main electrical sub-panel and turn off the circuit breakers for all pool equipment. This includes the primary filtration pump, booster pumps, salt chlorine generator, pool heater, automated chemical feeders, and underwater pool lights.

Warning: Running a pool heater or salt chlorinator without active water flow can cause explosive steam buildup or melt internal plumbing components. Running a traditional pool filtration pump dry will warp the impeller and destroy the mechanical shaft seals within minutes. Lock out and tag out these breakers to ensure they are not accidentally switched back on during the draining process.

Step 3: Configure and Position the Submersible Pump

Thread your 1.5-inch or 2-inch PVC lay-flat discharge hose onto the male discharge port of the submersible utility pump. Ensure the threads are clean and wrapped with two to three wraps of PTFE (Teflon) tape to create a watertight seal. Unroll the discharge hose completely, ensuring there are no kinks, sharp bends, or twists that could restrict water flow and build backpressure.

Tie a high-tensile nylon rope securely to the handle of the submersible pump.

Pro-Tip: Never lower or raise a submersible pump by its electrical power cord. Doing so breaks the watertight seal where the cord enters the motor housing, causing short circuits, pump failure, and severe electrocution hazards.

Lower the pump slowly into the deepest section of the pool using the nylon rope. If you are draining a vinyl-liner pool, place the pump inside a clean plastic bucket with holes drilled in the sides, or set the pump on a wide rubber mat. This distributes the weight of the pump and prevents its hard plastic or metal intake base from tearing or puncturing the vinyl liner under suction.

Step 4: Secure the Discharge Hose Terminal

Run the discharge hose to your designated disposal zone. If using your home’s sanitary sewer cleanout, locate the threaded pipe cap (usually found in the yard near the foundation or inside the basement mechanical room). Unscrew the cap and insert the discharge hose approximately 12 to 18 inches into the pipe.

Secure the hose firmly in place using sandbags or heavy-duty zip ties anchored to a fixed object. The force of water exiting a 2-inch hose at high velocity creates a powerful reaction force that can cause the hose to whip out of the drain pipe, causing major water damage to your property or home interior. Do not seal the pipe opening completely; allow a gap for air to escape so the sewer line does not back up into your home's sinks or toilets.

Step 5: Initiate the Drawdown and Monitor Flow

Plug the pump's heavy-duty extension cord into your GFCI-protected outlet. The pump should prime immediately and begin moving water. Walk the entire length of the discharge hose to verify there are no leaks or severe kinks. Check the sewer cleanout to ensure it is swallowing the water at the rate the pump is delivering it.

If the sewer pipe begins to overflow, you are exceeding its drainage capacity. In this scenario, install a ball valve on the discharge end of the pump to throttle back the flow rate, or swap the pump for a lower-output unit. Monitor the drawdown rate. A healthy drainage speed should drop the water level by roughly 1 to 2 feet per hour.

Step 6: Mitigate Hydrostatic Pressure Hazards

As the water level drops, the downward pressure holding the pool shell in the ground decreases. Keep a close eye on the pool floor and walls. If you notice the pool floor flexing upward, vinyl liner bubbling, or groundwater seeping through cracks, stop pumping immediately and refill the pool.

Once the water level drops to the deep end floor, locate the hydrostatic relief valve. This is typically a brass or plastic threaded plug located in the main drain pot or directly in the floor of the deep end. Use your T-bar wrench to unscrew and remove this plug.

Removing the plug allows groundwater beneath the pool to flow up into the pool shell, equalizing the pressure and preventing the pool from lifting out of the ground. Keep this plug out until you begin refilling the pool.

Step 7: Clean Up Residual Water

Submersible pumps will lose prime and stop drawing water when the depth reaches about 1/2 to 1 inch. To remove the remaining puddles, use a heavy-duty wet-dry vacuum with a high-capacity canister. Alternatively, use a squeegee to push the remaining water directly into the submersible pump's intake.

Once the pool is empty, unplug the pump, pull it out using the nylon rope, and begin your scheduled maintenance, plaster repairs, or liner replacements immediately.

Warning: Do not leave an empty concrete, fiberglass, or vinyl pool exposed to direct sunlight and high temperatures for more than 24 to 48 hours. Direct UV rays and heat can dry out plaster, cause fiberglass to warp, and shrink vinyl liners, making them split when the pool is refilled.

Technical Comparison of Pool Drainage Methods

The table below outlines the performance thresholds, safety risks, and mechanical limitations of the three primary methods used to drain swimming pools.

Troubleshooting Common Pool Drainage Failures

Operating water-pumping equipment under field conditions often presents mechanical and hydraulic challenges. Below are the most common failure scenarios and their technical solutions.

Scenario 1: The submersible pump runs but fails to move water

• Root Cause: Air lock in the pump impeller housing. When a pump is dropped straight down into the water, air can get trapped inside the volute, preventing the impeller from creating the pressure differential needed to draw water.
• Actionable Fix: Unplug the pump from the electrical source. Keeping the pump submerged, tilt it at a 45-degree angle to allow the trapped air bubbles to escape from the intake grate. Once the bubbling stops, set the pump flat on the pool floor and plug it back in. If it still fails to pump, check the intake screen for leaves, plastic wraps, or plaster chips and clear any obstructions.

Scenario 2: The drainage water backs up out of the sanitary sewer cleanout

• Root Cause: The flow rate of the submersible pump exceeds the physical carrying capacity of the home sewer line, or there is a blockage down-line in the lateral sewer pipe.
• Actionable Fix: Immediately unplug the pump to stop the flooding. Install an in-line PVC ball valve on the pump's discharge outlet to restrict and regulate the flow. Restart the pump with the valve partially closed, adjusting the flow down until the sewer pipe can manage the volume without overflowing. If backups continue at low flow rates, have your home sewer line inspected and snaked for root intrusions.

Scenario 3: The vinyl pool liner begins to wrinkle or pull away from the walls

• Root Cause: Loss of hydrostatic balance. Water pressure inside a vinyl pool keeps the liner pressed tight against the pool shell. When you remove the water, any groundwater behind the liner will push inward, causing wrinkles, bubbles, or complete liner slippage.
• Actionable Fix: Stop pumping water out immediately. Insert a specialized liner vacuum hose down behind the liner through a corner top track. Seal the insertion point with duct tape and turn on the vacuum to draw out the air and water trapped behind the liner. This vacuum pressure holds the liner tight against the wall while you complete your repairs or water adjustments.

Scenario 4: The pool shell shows signs of shifting, cracking, or lifting

• Root Cause: Hydrostatic pressure in the surrounding soil is higher than the weight of the water remaining in the pool, causing the pool structure to behave like a boat and float upward.
• Actionable Fix: Turn off the submersible pump immediately. Run multiple garden hoses from your home's water supply and begin refilling the pool as fast as possible to restore downward ballast. Locate the hydrostatic relief valve at the bottom of the pool and verify that it is open and functional, allowing groundwater to drain into the pool to equalize pressure.

Frequently Asked Questions

Can I use my pool's main filtration pump to drain the pool completely?

No, you should never use your pool's primary filtration pump to drain the pool completely. These pumps are designed to operate in a closed, flooded system. Once the water level drops below the skimmer mouth, the pump will draw air, lose its prime, and run dry. This causes rapid overheating, melting the pump basket, warping the impeller, and destroying the shaft seal, which leads to costly motor failure.

How long can I safely leave my pool empty?

You should leave your pool empty for the shortest time possible, ideally no more than 24 to 48 hours. Prolonged exposure to sun, wind, and ambient heat can cause vinyl liners to shrink and split, fiberglass shells to warp and crack, and concrete plaster finishes to dry out, delaminate, and pop off the gunite base.

What is the safest time of year to pump out a pool?

The safest time to pump out a pool is during cool, dry weather when the water table is at its lowest point. Avoid draining your pool during the rainy spring season, immediately after major storms, or during hot summer days with temperatures exceeding 85°F (29°C).

Where can I legally pump my pool water?

The safest and most legally compliant location to discharge pool water is your home’s sanitary sewer cleanout. Most local municipal codes strictly prohibit discharging pool water into public storm sewers because of the environmental threat that pool sanitizers and copper-based algaecides pose to local waterways and aquatic life.

Professional Pool Equipment and Maintenance Services

For complex drainage projects, high water tables, or delicate vinyl-liner adjustments, relying on commercial-grade extraction systems is the safest path forward. Browse our selection of professional-grade submersible pumps and heavy-duty lay-flat hoses today to ensure your next pool drawdown is safe, fast, and trouble-free.