It is common for an above-ground pool to be slightly out of level after its first winter, but it is not technically “normal” in terms of ideal structural health. Most experts agree that a deviation of one inch or less across the diameter of the pool is acceptable due to natural ground settling and the weight of the water. However, if the pool has shifted more than two inches, it poses a significant risk to the structural integrity of the wall and the liner. At CND Installers, we frequently see this occur in the Mid-Atlantic region where freeze-thaw cycles in Maryland and Pennsylvania cause the soil to expand and contract, leading to minor shifts in the pool’s foundation.
Quick Solution: The One-Inch Rule
If your pool is less than one inch out of level, the most effective immediate action is to monitor the site throughout the spring. As the ground dries and the water temperature rises, minor settling often stabilizes. Ensure the uprights are still vertical and the bottom track remains fully supported. If the deviation exceeds one inch, you must partially drain the pool and shim the low-side uprights or re-level the patio blocks to prevent a catastrophic wall failure.
Diagnostic: Why Did My Pool Shift?
Understanding why a pool has shifted is critical to determining if the movement is a one-time settling event or a recurring drainage issue. The weight of a 24-foot round pool can exceed 100,000 pounds, putting immense pressure on the virgin or compacted soil beneath it. When the ground freezes in winter, moisture in the soil turns to ice and expandsâa process known as frost heave. This can lift sections of the pool unevenly, especially if the site was not excavated down to a solid, undisturbed clay or mineral base.
| Cause of Leveling Issue | Severity | Common Indicators |
|---|---|---|
| Natural Settling | Low | Deviation < 1 inch; no visible wall buckling. |
| Frost Heave | Medium | Visible gaps under the bottom track; shifts occur after first thaw. |
| Erosion/Washout | High | Soil missing from under the track; pool leans toward a slope. |
| Improper Compaction | High | Significant sinking on one side; wall creases or “kinks.” |
5 Solutions for an Out-of-Level Pool
1. Monitor and Document the Deviation
Before taking invasive action, measure the distance from the water level to the top rail at various points around the perimeter. If the difference is between 0.5 and 1 inch, simply record these numbers and check them again in two weeks. If the numbers remain static, the pool has likely finished its initial settling phase. This is a common occurrence for new owners in Pennsylvania and Maryland who are experiencing their first full seasonal transition.
2. Reinforce the Base with Crushed Stone
If you notice minor “washout” where the soil has eroded from under the pool track, you can reinforce the perimeter without draining the water. Pack crushed stone or stone dust tightly under the bottom track and around the patio blocks. This provides a stable, non-porous foundation that is less susceptible to future frost heave than standard topsoil or sand.
3. Adjust the Upright Supports (Shimming)
For pools that are 1 to 1.5 inches out of level, you may need to adjust the individual uprights. This involves draining the pool to about 12 inches of water to reduce weight. You can then carefully use a pry bar to lift the low-side uprights and slide pressure-treated wood shims or plastic spacers under the base plate. Never shim more than an inch, as this can create a pivot point that stresses the pool wall.
4. Correcting the “High Side” Excavation
In cases where the pool is significantly out of level (2+ inches), the only permanent fix is to lower the high side. This requires draining the pool and pulling the liner back. You must excavate the earth from the high side until it matches the low side. It is a common mistake to try and “build up” the low side with loose dirt; however, loose fill will always compress under the weight of the water, leading to the same problem next year.
5. Professional Re-Leveling and Reset
If the pool wall shows signs of buckling or if the liner is pulling away from the track, a professional reset is required. Companies like CND Installers specialize in correcting these structural issues by laser-leveling the entire site to within 1/8th of an inch. This process often involves removing the liner, re-grading the sand base, and ensuring all patio blocks are recessed and level with the virgin soil.
Advanced Troubleshooting for Edge Cases
In some instances, a pool may appear out of level when the foundation is actually straight. This can happen if the liner was installed unevenly, causing the pattern to look “crooked” against the water line. Always measure from the water to the metal frame, not the liner pattern. Additionally, if you live in an area with high water tables, “floating liners” can occur during the spring thaw, making the pool floor feel lumpy or unlevel even if the exterior walls are perfectly straight.
Prevention Tips for Future Seasons
- Improve Drainage: Ensure that gutters and landscape runoff are directed away from the pool base to prevent soil softening.
- Winterize Correctly: Use a properly fitted winter cover and air pillow to distribute ice weight evenly across the surface.
- Maintain a 6-inch Cove: Ensure your pool has a solid earth or foam cove inside the wall to prevent the liner from shifting and pulling on the walls during freezes.
- Annual Inspections: Every spring, walk the perimeter and look for “sinkholes” or gaps between the bottom track and the ground.
Related Reading
For a comprehensive overview of this topic, see our The Complete Guide to Above Ground Pool Selection and Professional Installation in 2026: Everything You Need to Know.
You may also find these related articles helpful:
- How to Determine if Your Yard Slope Requires Professional Excavation: 5-Step Guide 2026
- Is Burying an Above Ground Pool 2 Feet Worth It? 2026 Cost, Benefits & Verdict
- Aluminum vs. Resin: Which Pool Material Is Better for Salt Systems? 2026
FAQ
Frequently asked questions for this article
How many inches out of level is dangerous for an above ground pool?
A pool is considered dangerously out of level if the deviation exceeds 2 inches. At this point, the uneven pressure can cause the wall to buckle or the uprights to fail, potentially leading to a total collapse.
Can I level my pool without draining it?
While you can shim the uprights for minor adjustments (under 1 inch), you should never try to level the entire pool while it is full. The weight of the water makes it impossible to move the track safely and could result in injury or equipment damage.
Is it okay to use sand to level the low side of the pool?
No, you should never use sand to level the base of an above ground pool. Sand is used only for the interior floor (the ‘cushion’). The actual track and supports must sit on firm, compacted earth or patio blocks to prevent sinking.
What is the acceptable tolerance for an out-of-level pool?
Most manufacturers recommend a tolerance of 1 inch. If your pool is within this range after the first winter, it is generally considered safe to use, provided there are no visible signs of wall stress or leaning.
