Yes—an empty pool can lift or “float” if groundwater pressure builds underneath it. Matt has seen it happen. His comparison is simple: without the weight of the water inside, a pool shell can behave more like a boat when enough water gets underneath it.
Why rain matters when a pool is drained
A filled pool contains a tremendous amount of water weight. When the pool is drained, that downward weight disappears. If heavy rain or a high water table creates enough upward groundwater pressure below the shell, the pressure can lift the structure.
This is why Matt pays close attention to weather when a renovation or structural repair requires a pool to remain empty. Pentair likewise advises against draining a pool in high-water-table conditions because an empty pool can pop out of the ground.
What can be damaged if the shell moves?
The shell itself is only part of the problem. Matt has seen situations where a pool shell moved and the surrounding systems took the damage:
- underground plumbing and piping
- waterline tile
- coping and bond-beam transitions
- decking and joints around the pool
- structural connections and repaired areas
In a severe case, the amount of movement can make localized repair impractical and turn the project into a rebuild.
Matt's field rule during rainy conditions
Matt says a pool can sometimes remain drained during reliably dry conditions, but rainy weather changes the risk calculation. When project conditions allow, retaining or adding water can provide additional weight against groundwater pressure. On structural-repair jobs, contractors may also create groundwater-relief openings or use existing hydrostatic-relief methods so water beneath the shell has a path to relieve pressure.
How this affects structural crack repair
Matt says repairing the visible crack is usually not the most difficult part. The real job is figuring out why the shell cracked and correcting that cause first. If the cause is not repaired, stress can show up somewhere else in the shell.
Possible causes he looks for include shifting or eroded soil, loss of support beneath the gunite, a shell that was installed too thin, gunite/concrete that did not achieve the intended strength, and inadequate structural-steel size or spacing for the conditions.
How does Matt investigate the cause?
Sometimes there are clues before demolition: separation where decking meets coping, changes in elevation, or a waterline that is visibly out of level. But in Matt's field process, a significant structural problem often has to be opened up to understand what is happening underneath the gunite shell.
After the pool is drained and the affected area is opened, Matt can inspect for eroded soil, voids, shifting subsoil and the construction of the shell itself. That information guides the actual repair instead of simply covering the symptom.
Rain and cold can also extend the repair schedule
Even when flotation is controlled, wet weather can slow access, excavation, subsoil work and repair materials. Cold temperatures can affect scheduling as well. That is why Matt's structural-repair timelines are planning ranges rather than promises made before the pool is opened.
Read Matt's structural pool crack repair guide → Pool remodeling & renovation →
Additional reference
Pentair advises homeowners not to drain pools where the water table is high because removing the water can allow the pool to pop out of the ground. This supports the same groundwater-pressure concern Matt sees in the field.
Pentair: Why not to drain a pool when groundwater is a concern →
Frequently asked questions
Can an empty concrete pool pop out of the ground?
Yes. If groundwater pressure beneath a drained shell becomes high enough, the shell can lift or 'float.' The risk depends on groundwater, soil, drainage, pool construction and site conditions.
Is it safe to drain a pool before heavy rain?
Draining a pool during wet conditions can increase flotation risk, especially where groundwater can rise. Matt plans drain-down work around weather and site conditions and does not recommend homeowners drain a pool on their own without understanding the risk.
Why does water in the pool help?
The weight of pool water helps resist upward groundwater pressure. Matt sometimes keeps or adds water during wet conditions when project circumstances allow, but the correct amount and method are project-specific.
What happens if a pool shell lifts?
Matt has seen shell movement damage plumbing, piping, tile, coping and surrounding decking even when the shell itself remained repairable.
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