Owning an inground pool is a luxurious addition to any home, providing relaxation, recreation, and even a boost to property value. However, circumstances may arise—whether due to renovations, repairs, or seasonal changes—where you might need to leave your inground pool without water for an extended period. A pressing concern for many pool owners is just how long a pool can remain empty without suffering damage or requiring costly repairs.
This article dives deep into the question: how long can an inground pool sit without water? We’ll explore the factors that determine safe empty pool durations, delve into the effects of leaving a pool empty for too long, and provide best practices to protect your investment during such periods.
Understanding the Risks of Draining an Inground Pool
Before discussing the duration limits, it’s essential to understand what happens when you drain an inground pool. The structure of the pool—whether it’s made from concrete, vinyl, or fiberglass—reacts differently to being empty, and various environmental and structural forces come into play.
Hydrostatic Pressure and Groundwater Risks
One of the most critical concerns when draining an inground pool is hydrostatic pressure. In many areas, especially those with high water tables or heavy groundwater flow, the pressure from the surrounding soil and underground water can push upward on the pool’s bottom. If the pool is empty, the structure lacks the weight of water to counteract this pressure, often resulting in:
- Popping of the pool from its foundation
- Cracks in the shell or liner
- Severe structural damage requiring costly repairs
Hydrostatic pressure is a silent but powerful force. In some cases, a pool can lift out of the ground completely if not properly anchored or drained cautiously.
Material Type Determines Vulnerability
The type of pool you own can also influence how long it can safely sit empty:
| Pool Type | Vulnerability When Empty |
|---|---|
| Concrete (Gunite/Shotcrete) | High risk due to weight and reliance on water pressure for structural support |
| Vinyl Liner | Moderate risk due to potential shrinking or warping of the liner |
| Fiberglass | Low to moderate risk; resistant to hydrostatic issues but may shift |
Each material type has unique considerations, especially when it comes to long-term emptying.
How Long Can a Pool Stay Empty Safely?
While there’s no one-size-fits-all answer, there are general guidelines pool owners can follow, depending on pool type and environmental conditions.
Time Limits Based on Pool Material
- Concrete pools should ideally not be empty for more than 7–10 days, especially in areas with high groundwater levels. However, the presence of a hydrostatic relief valve may permit slightly longer periods.
- Vinyl pools should not sit empty longer than 7 days, as the liner can shrink, become brittle, or tear.
- Fiberglass pools can generally withstand being empty for up to 10–14 days without major issues, provided there are no groundwater concerns.
These timelines can vary depending on the climate, regional water table, and the professional guidance received before draining the pool.
Season and Climate Impacts on Safe Draining
Warm, sunny climates can present additional challenges due to:
- Thermal expansion causing warping or cracks
- Increased evaporation from open water-bearing soils which can affect concrete pool shells
Cold climates add their own risks, such as:
- Moisture behind the walls freezing and expanding, causing damage
- Ice heaving under vinyl liners
In general, it’s advisable to avoid leaving a pool empty during the hottest or coldest months unless necessary.
Groundwater Level: The Silent Enemy
Before draining your pool, it’s highly recommended to consult with a professional pool contractor to determine the local groundwater level. In regions with seasonal water flow or high precipitation, hydrostatic damage can occur within days of the pool being emptied. The best rule of thumb is: if you’re not sure, it’s better to partially drain or leave the water in place.
Consequences of Leaving a Pool Empty Too Long
If your pool sits empty too long, you risk costly damage and repairs. Here are the most common consequences:
Structural Damage
When the pool shell is empty:
- Cracks and voids appear in concrete pools
- The fiberglass shell might bend or pull away from the surrounding structure
- The vinyl liner is at risk of tearing or becoming unusable
Costly Repairs
Structural damage often leads to:
- Reconstruction of the pool walls or entire shell
- Replacement of liners and fittings
- Resurfacing concrete pools
- Reinstating the foundation and patio layout
These types of repairs can cost thousands of dollars and may not be fully covered by insurance if the damage stemmed from poor maintenance decisions.
Loss of Pool Features
When pools are emptied, submerged items or fixtures may be affected:
- Pool lights can malfunction when dry
- Skimmers, drains, and return jets may break
- Tile work at the waterline may detach due to temperature changes
Unwanted Algae and Debris Accumulation
Though the pool is empty, organic material like leaves, dust, and moisture can still enter. This can lead to:
- Mold and mildew growth in damp corners
- Algae starting to grow during humidity or rain
- Pests using the empty basin for habitation
Best Practices for Draining and Storing an Inground Pool
If an emptying becomes necessary, following the right protocol can significantly reduce the risk of damage.
Consult a Professional First
Before pulling the plug on your pool, consult with a licensed pool contractor. They’ll:
- Assess the risk of hydrostatic pressure
- Recommend the safest time to drain
- Determine if a hydrostatic relief valve needs to be installed or used
Install or Check Hydrostatic Relief Valves
These one-way valves are typically located in the main drain and help release pressure from groundwater beneath the pool floor. A properly functioning valve is crucial when the pool is drained or partially emptied.
Don’t Fully Drain If Not Necessary
If you’re cleaning or repairing the surface (tile line, plaster, etc.) consider a partial drain instead. This method:
- Minimizes structural risk
- Keeps hydrostatic balance in check
- Allows access to the necessary parts below the waterline
Monitor Weather Conditions
Avoid draining during heavy rain seasons or extreme summer heat. The ideal window is usually during mild temperature months.
Timing Tips:
- Check long-range forecasts to ensure no major weather changes
- Drain in the early morning to monitor the process
- Minimize exposure to extreme sun or frost
Protect the Pool Interior
Once empty:
- Cover the exposed surfaces to prevent UV degradation
- If using a vinyl liner, cover it fully—sunlight accelerates wear
- Clean and dry the interior thoroughly to prevent mold or algae growth
Keep the Drain Open and Functional
Ensure that all gutters, external pool drains, and surrounding landscaping drainage remain functional. Stagnant water pooling around the shell adds pressure and risk.
Situational Considerations for Draining Pools
There are several scenarios in which draining an inground pool becomes necessary. Below are a few of them, along with expert advice on how long you can safely leave your pool empty.
Refurbishing the Pool
If your concrete pool has cracked or your tile work is deteriorating, a full drain may be required. However, limit the time the pool sits empty:
- For plaster repairs: Max 5–7 days
- For new tile installation: Around 7–10 days
Coordinate with professionals to ensure the pool is refilled as soon as these tasks are completed.
Winterization and Seasonal Closure
During winter, inground pools need special care:
- In many climates, especially those prone to freezing, leaving water in the pool is better than draining it.
- Using proper winterizing chemicals and covers ensures the structure and lining stay protected.
- Draining a pool for seasonal storage should only be done with expert guidance and preparation.
Emergency Repairs
In situations like equipment failure or plumbing issues, sometimes partial or full draining becomes unavoidable.
- If the issue can be repaired in 1–2 days, leaving the pool drained is usually safe.
- For longer repairs, consider pumping water back in temporarily unless the work specifically requires an empty pool.
Conclusion: Balancing Safety and Practicality
Leaving an inground pool without water is not inherently dangerous, but the risks are real and depend on several key variables:
- The design and material construction of your pool
- The groundwater level and local environmental conditions
- The duration and reason for draining
To stay safe, pool owners should:
- Never leave a pool empty for more than 7–14 days without professional consultation
- Monitor for signs of pressure, cracks, or shifting
- Re-fill the pool as soon as repairs or maintenance are completed
By taking informed, proactive steps, you can ensure your inground pool remains in excellent condition—whether it’s full of water or temporarily empty.
Remember, your pool is a long-term investment. Knowing how long can an inground pool sit without water not only saves money in the long run but also extends the life of your backyard oasis.
Can an inground pool safely sit empty for a long time?
Leaving an inground pool empty for an extended period is generally not recommended due to the risk of structural damage. Without water, the hydrostatic pressure from groundwater can push the pool up from the bottom or cause cracks in the walls. This is especially true for fiberglass and vinyl-lined pools, which rely on the weight of water to stay in place and maintain the integrity of the structure. The duration a pool can remain empty without damage depends on various factors, including the groundwater level in your area and the type of pool construction.
For concrete (gunite) pools, the risk of shifting is lower compared to other types, but still present. Additionally, empty pools are vulnerable to other forms of damage, such as cracks from temperature changes or root intrusion from nearby plants. If it’s necessary to drain the pool, especially for repairs or winterization, it’s important to consult a professional. They can provide guidance on whether hydrostatic relief is needed or whether the pool should be partially filled or monitored during dry periods.
How long can an inground vinyl pool sit without water?
An inground vinyl pool should not be left without water for longer than a few days, and even that can pose a risk. The vinyl liner is designed to remain stretched and supported by water. When left dry, the liner can shrink or become brittle, making it prone to tearing when the pool is refilled. In addition, the lack of water removes downward pressure that helps keep the structure of the pool in place. Groundwater pressure can then cause the pool walls to collapse or the floor to heave upward.
If the vinyl pool must be drained for any reason, such as replacing the liner or completing repairs, it’s crucial to do so under the supervision of a pool professional. In some cases, professionals may recommend placing water bags in the pool or keeping the pool partially filled to counteract soil pressure. While short-term draining is avoidable for repairs, long-term storage without water is discouraged due to the high risk of irreversible damage to the liner and overall pool structure.
What are the risks of leaving a fiberglass pool empty for too long?
Fiberglass inground pools are particularly vulnerable to damage when left empty. Designed to have the hydrostatic pressure of water balancing the forces acting on the shell structure, a fiberglass pool can easily “pop” out of the ground if left dry during periods of high groundwater levels. Even when hydrostatic pressure isn’t a concern, the fiberglass shell can become brittle or warp due to prolonged exposure to air and sunlight.
Another issue is that the weight of the surrounding soil can compress or distort the pool walls if the internal water pressure is absent. In addition, seals around returns, skimmers, and lights might dry out, leading to leaks or failures. If a fiberglass pool must be emptied—even briefly—it should be done with precautions such as the installation of hydrostatic plugs and close monitoring of groundwater levels. Professional supervision is highly recommended to ensure the long-term viability of the fiberglass structure.
How long can a concrete (gunite) pool sit without water?
Concrete or gunite pools are more structurally resilient than other types and can typically sit empty for longer periods. However, while the pool shell is strong, it is still at risk depending on the surrounding environment. In areas with high groundwater tables, a gunite pool can float upward or crack, especially if drained completely and suddenly. Without the downward force of the water inside, it faces unopposed pressure from the surrounding soil and water beneath the floor.
In more arid climates where groundwater levels are low, a concrete pool might sit empty for up to several weeks without immediate structural concerns. However, other issues such as surface cracking due to temperature changes or freeze-thaw cycles can occur over time. Additionally, equipment like plaster finishes in the pool can be damaged if the structure shifts or dries out unevenly. Even though gunite structures are generally safer when empty, homeowners should exercise caution and consult professionals, especially if the pool is to be left dry for months.
Is it safe to leave an inground pool empty during winter?
Leaving an inground pool empty during winter is generally not advised, as freezing temperatures and shifting soil can severely damage the structure of the pool. Water within the ground around the pool can freeze and expand, exerting pressure on pool walls and the floor. Without water inside to balance this force, structural deformation—including cracks, shifting, and even complete heaving of the pool floor—is highly likely. Even drained water lines can pose a risk of freeze damage.
Furthermore, the absence of water allows temperature extremes to impact the pool’s interior surfaces and mechanical systems more directly. Fiberglass, vinyl, and concrete pools are particularly vulnerable under these conditions. If draining is absolutely necessary—for example, for repairs—it’s important to winterize the equipment, inspect for hydrostatic pressure risks, and consult with a pool professional to ensure proper precautions are taken. A winter cover can also offer some protection if the pool is only partially drained.
What precautions should be taken if draining an inground pool temporarily?
If you need to drain your inground pool temporarily—for maintenance, repair, or remodeling—there are several key precautions to follow. First, consult a licensed pool professional before draining the pool. They can assess groundwater conditions and determine if hydrostatic relief valves need to be installed to prevent the pool from popping out of the ground. A professional may also suggest installing water bags or leaving a small amount of water in the pool to counteract external forces.
In addition to structural concerns, you should take steps to protect pool surfaces and equipment. Cover exposed areas to prevent weather damage and use protective coatings where necessary. Check plumbing lines and pumps to ensure they are properly secured or drained to avoid freeze damage. Finally, monitor weather forecasts, groundwater levels, and soil conditions regularly while the pool is empty, especially during periods of heavy rain or extreme cold. Taking these steps can help mitigate damage during temporary draining.
How does groundwater affect an empty inground pool?
Groundwater can have a major impact on an empty inground pool, particularly by creating upward pressure against the pool floor. If the water table in the area rises, the groundwater beneath the pool can push upward on the structure while the absence of water inside removes the counteracting downward force. This imbalance can cause the pool bottom to lift or crack, a phenomenon commonly referred to as “pool popping.” Vinyl and fiberglass pools are especially prone to structural displacement in such situations.
The risk of groundwater damage depends largely on location, recent weather patterns, and the time of year. Areas with poor drainage or proximity to bodies of water often experience higher groundwater levels. To prevent such issues, many pool contractors recommend inserting hydrostatic relief plugs before draining a pool, allowing water to enter the hydrostatic valve and balance pressure. Ignoring groundwater risks can lead to costly repairs, so understanding local soil and water conditions is essential when considering draining your inground pool.