Emptying an inground pool is often an overlooked or misunderstood process, with many pool owners not realizing the complexities involved beyond simply draining the water. Whether you’re preparing for a renovation, winterizing your pool, or dealing with a chemical imbalance, knowing what happens when you empty your pool can help prevent damage, costly repairs, and maintenance pitfalls. In this comprehensive guide, we’ll break down every stage and consequence of emptying an inground pool, equipping you with the knowledge to make informed decisions.
Why Would You Empty an Inground Pool?
Before exploring the process and consequences, it’s important to understand why someone would choose to empty their pool in the first place. There are several valid reasons:
- Renovations or Repairs: Major structural repairs, resurfacing, or tile replacement often require the water to be completely or partially drained.
- Winterization: In colder climates, some pool systems require partial draining to prevent freezing damage, but full draining is typically not recommended for inground pools.
- Chemical Contamination: Extreme chemical imbalances or contamination with substances like oil, algae overgrowth, or harsh cleaning agents may necessitate a full drain.
- Water Quality Issues: Persistent cloudiness, odor, or staining that cannot be resolved through standard chemical treatments might prompt owners to empty the pool.
- Sediment or Debris Buildup: Pools that have not been cleaned regularly might accumulate dirt, leaves, and mineral deposits that are difficult to address with traditional methods.
Each scenario requires careful consideration, especially since draining an inground pool is not a simple process and can introduce risks that are easy to overlook.
The Mechanics of Draining Your Pool
Draining an inground pool might seem as straightforward as flipping a switch, but the actual process involves several methods and varying levels of complexity.
Common Drainage Methods
1. Manual Pumping: The most common method involves using submersible or sump pumps, which slowly pump the water out through a hose. This is typically the safest and most controlled option.
2. Backwashing the Filter: While often used for partial water removal, backwashing is designed to clean the filtration system—not to empty the pool entirely. It’s inefficient and impractical for a full drain.
3. Municipal or Septic Drainage: Pool owners must be aware of local regulations regarding where pool water can be discharged. Some areas require the water to go into storm drains, while others may allow lawn or sewer systems—though highly chlorinated water is generally prohibited.
Duration and Water Volume
The time it takes to empty a pool depends largely on its size and the type of pump used. A standard residential inground pool holds between 15,000 and 30,000 gallons of water. A submersible pump with a flow rate of 70 gallons per minute would take 3.5 to 7 hours to fully drain the pool. However, if multiple pumps are used and the water is discharged into the city sewer system directly, you may have to contend with additional restrictions or slow flow rates depending on your area’s regulations.
The Hidden Risks of Emptying an Inground Pool
Emptying an inground pool—if done correctly and under the right conditions—is manageable. However, it comes with several risks that could jeopardize the structural integrity of the pool, your property, or the environment.
Risk of Pool Lift
Hydrostatic pressure is a key factor to understand. This pressure from the surrounding groundwater works against the pool’s structure, pushing on its walls and floor. In normal operation, the water inside the pool balances this pressure. When the pool is drained, the pressure from below can literally “lift” the pool out of the ground, especially in areas with heavy rain or high water tables.
This phenomenon—especially common in fiberglass and vinyl-lined pools—is known as “pool popping” and is expensive to repair. To mitigate this risk, professionals usually pump water out in stages and check hydrostatic valves regularly.
| Pool Type | Floatation Risk | Recommended Precautions |
|---|---|---|
| Concrete | Moderate | Check hydrostatic valves; avoid sudden drainage during rainy periods |
| Fiberglass | High | Must have proper hydrostatic relief, avoid draining completely unless absolutely necessary |
| Vinyl Liner | High | Drain only for repairs, use professional services; avoid cold, wet seasons |
Impact on Pool Surfaces and Components
Emptying your pool too quickly or without proper precautions can damage the interior finishes.
- Concrete pools: The plaster or quartz surface can dry unevenly, leading to cracking or “spider cracking.”
- Fiberglass pools: The gel coat can blister or delaminate when exposed to sunlight and heat without water.
- Vinyl pools: Prolonged exposure to air and sunlight can cause the vinyl liner to shrink, fade, or bulge when refilled.
If you are planning a long-term drain, especially during summer, covering the pool floor and walls with a tarp can protect sensitive surfaces and reduce UV damage.
Chemical Damage During Refill
Draining a pool because of chemical imbalance does not solve the root cause. In fact, simply replacing the water won’t necessarily fix pH or chlorine issues. It’s often better to dilute the old water with fresh water, particularly for swimming pool owners trying to correct high calcium hardness or total dissolved solids (TDS). Failure to check water chemistry before and after draining can lead to costly damage when refilling the pool.
Environmental and Legal Considerations
Draining your pool improperly can violate local ordinances or harm the environment due to the high concentration of chlorine and other chemicals in the water.
Water Disposal Regulations
Cities and municipalities often have strict guidelines for dumping chlorinated water into public sewers or storm drains. Some areas limit the chlorine level to below 0.1 ppm before water can be discharged. It’s essential to contact your local environmental or water authority to:
- Confirm acceptable discharge methods.
- Find out how much water you can legally release at once.
- Learn whether dechlorination is required before draining.
Remember: Discharging pool water directly onto your property without proper preparation can cause damage to your lawn, kill nearby plants, or erode soil structures.
Use of Dechlorination Methods
To safely drain a pool with chlorine-heavy water, consider using sodium thiosulfate or other dechlorination chemicals. This can neutralize chlorine before the water hits the ground or sewer system. Always test the water with a reliable test kit before disposal to ensure chlorine levels meet local legal limits.
Special Considerations by Pool Type
Different types of inground pools have unique characteristics that influence how and why you should, or shouldn’t, empty them.
Concrete/Gunite Pools
These pools are the most robust and can tolerate occasional draining better than other types, but even they are not immune to damage:
- Must have functional hydrostatic relief valves.
- Should not be left empty for more than 24 hours during high-water table seasons.
- Draining may be necessary for surface renovations like replastering or crack repair.
While some pool companies recommend keeping a foot or so of water at the bottom during a full drain, always consult a technician for safety precautions.
Fiberglass Pools
Fiberglass pools are the most vulnerable to floating and UV damage. Due to their one-piece shell:
- Complete draining should be done only under professional guidance.
- Exposing the shell to sunlight for even a single day during summer must be avoided to prevent surface blistering.
In most cases, repairs and cleaning can be handled without full drainage when working on a fiberglass pool.
Vinyl Liner Pools
The vinyl lining in these pools is vulnerable to stretching, shrinking, and punctures when the pool is empty:
- Draining should only occur during necessary repairs or liner replacement.
- Always keep the pool covered in sun-exposed periods to minimize damage.
After a complete drain, check the sand or vermiculite layer under the liner for debris or uneven sections to prevent wear or folds when refilling.
What You Should Do Before and After Draining
Proper preparation and follow-up are vital to ensuring that your pool remains intact and ready for the next swim season.
Before Draining
- Consult a pool professional: Always get advice based on your specific pool type, location, and reason for draining.
- Prepare the area: Ensure the discharge hose has a clear path without damaging landscaping or city infrastructure.
- Turn off all pool equipment: Disconnect pumps, heaters, and filters before starting the drain.
- Test the water: Ensure chemical levels are within legal guidelines before disposal.
After Draining
- Inspect the structure: Look for cracks, signs of hydrostatic pressure issues, or wear on liners or finishes.
- Start the refill process cautiously: When refilling, ensure plumbing is restored and water chemistry is balanced before completely filling.
- Rebalance the water chemistry: Test with a full spectrum kit and start adding chemicals as soon as you begin refilling.
- Clean surfaces: Perform a thorough brushing and pressure washing of the pool before refilling to remove algae, debris, or calcium deposits.
Alternatives to Draining an Inground Pool
In many cases, complete drainage may not be the best solution. There are alternatives that can solve common pool issues without the risk.
Dilution: Instead of draining entirely, pumping out a portion of the water and refilling can help correct chemical concentrations like calcium hardness and TDS.
Shock Treatments: For algae blooms or bacterial issues, a strong chlorine or non-chlorine shock can resolve contamination without wasting water.
Use of Water Clarifiers: If your pool is cloudy due to fine particulates, using a clarifier can speed up filtration and improve water clarity without full drainage.
Partial Water Replacement: As part of routine maintenance, especially before winterization or reopening, partial draining and refilling can boost water quality without the need to fully empty.
Final Thoughts: Draining Your Pool Is Serious Business
Emptying an inground pool goes far beyond simply pulling the plug. It’s a process that involves structural, chemical, legal, and environmental responsibilities. Missteps can lead to costly repairs, wasted water, or regulatory fines.
By understanding the reasons behind draining, the mechanics of removal, and the risks and responsibilities involved, you can keep your pool healthy and functional for years to come. Whether it’s a full drain or a partial water change, always approach this task with preparation, care, and—if necessary—the help of professional pool services.
Key Takeaways:
- Draining is necessary only for repairs, contamination, or liner issues.
- Pool type determines the risks and precautions you must take.
- Never drain during rainy seasons or high groundwater levels without consulting a professional.
- Chemical balance before and after is critical to long-term pool health.
- Proper disposal and environmental compliance are legal obligations.
So before you reach for the pump, make sure the decision to drain was well-informed, well-prepared, and absolutely necessary.
What are the risks of emptying an inground pool?
Emptying an inground pool can pose several risks, especially if not done properly. One of the main concerns is structural damage. When a pool is drained, the water pressure from the surrounding soil and groundwater can cause the pool to shift, crack, or even pop out of the ground. This risk is particularly high in areas with high water tables or after heavy rains when groundwater levels are elevated.
Additionally, the interior surfaces of the pool, such as plaster or tile, can become damaged when exposed to air for extended periods. These materials may dry out, leading to cracking or delamination. Vinyl-lined pools are especially vulnerable since the liner can shrink or warp without water to keep it stretched. Professionals typically recommend keeping at least some water in the pool during draining processes to counteract these risks.
Why might someone need to empty an inground pool completely?
There are several reasons someone may need to fully drain an inground pool. Major renovations like resurfacing the pool shell, repairing structural cracks, or replacing plumbing lines underneath the pool often require complete drainage. In some cases, severe algae infestations or chemical imbalances that cannot be corrected through partial draining and treatment may warrant emptying the entire pool.
Another common reason for total pool drainage is the replacement or repair of a vinyl liner. To properly install a new liner, the old one must be removed, and the pool must be dry to ensure a proper fit and seal. Similarly, when closing a pool for the winter in certain climates, or if a pool has suffered structural damage from freezing temperatures, a full drain might be necessary to prevent further harm and prepare for repairs.
How long can an inground pool safely remain empty?
The length of time an inground pool can remain empty depends on several factors, including its construction type, local groundwater levels, and climate conditions. In ideal circumstances, it’s best not to leave a pool empty for more than a few days. Prolonged exposure to air and sunlight can cause damage to the pool’s interior finish and plumbing components.
For concrete or gunite pools, which are more durable, professionals sometimes recommend keeping at least 18–24 inches of water in the pool to help counteract hydrostatic pressure from groundwater. Fiberglass and vinyl pools are more sensitive and should not be left empty for more than 24–48 hours unless under expert supervision. Always consult a professional before draining your pool for any extended period.
Can an inground pool pop out of the ground when empty?
Yes, an inground pool can absolutely “pop out” of the ground when it’s drained completely. This phenomenon, known as hydrostatic uplift, occurs when groundwater surrounding the pool creates upward pressure. Without the weight of the water in the pool to balance this pressure, the structure can be pushed upward, causing severe damage to the pool walls, plumbing, and surrounding landscaping.
This is most common after heavy rains or in areas with high water tables. Even a small amount of water left in the pool can help counteract this risk. To prevent hydrostatic uplift, some pool professionals install hydrostatic relief valves that allow groundwater to enter the pool and equalize pressure when the pool is partially drained. Always assess local water conditions before emptying a pool.
What should be done before emptying an inground pool?
Before emptying an inground pool, it’s important to take several precautions to avoid costly damage. First, check the local water table and weather conditions. Avoid draining your pool during or after heavy rains when groundwater levels are high. If possible, consult with a professional pool contractor or engineer to determine whether it’s safe to drain the pool completely.
Also, inspect the pool’s plumbing and equipment systems. If you’re draining for repairs or maintenance, make sure all equipment is properly turned off and winterized if necessary. If the pool has a main drain, ensure it has a hydrostatic relief valve, which can help equalize pressure if groundwater rises during the draining process. Leaving a small amount of water in the pool or using specialized bracing may also be advisable depending on your location and pool type.
How do I safely drain an inground pool?
Draining an inground pool should be done carefully to avoid structural damage or safety hazards. Begin by checking local groundwater conditions as mentioned before. Then, use a submersible pump or rent a professional-grade pump from a pool supply store. Avoid using the pool’s own filtration system to drain the water, as it’s not designed for this task and could cause damage or flooding.
It’s also essential to direct water away from the pool area and your home’s foundation to prevent waterlogging the surrounding soil, which can worsen hydrostatic pressure. If you’re only doing minor repairs or cleaning, consider partial draining instead of completely emptying the pool. For complete drainage, monitor the process closely and leave the skimmer and return lines open (if applicable) to help relieve pressure. When in doubt, hire a professional.
What happens to a pool’s equipment when the pool is emptied?
When an inground pool is emptied, the pool equipment such as the pump, filter, and heater should also be turned off and possibly winterized, especially if the pool will remain empty for a long time. Leaving the filtration system running without water can cause the pump to overheat and suffer internal damage. It’s important to shut off the breaker to the equipment to avoid accidental operation.
In some cases, especially during winterization or long-term maintenance projects, the plumbing lines should also be blown out with air to remove any remaining water and prevent freezing and cracking. Chemical feeders and automatic pool cleaners connected to the system should be disconnected and stored properly. When refilling the pool, these systems must be checked and properly restarted to ensure they function safely and effectively.