While this isn't a super common issue, concrete pools can float when groundwater pressure beneath the pool becomes strong enough to push upward against the structure.
The good news is that pool builders understand this risk and use specific construction methods to help prevent it.
In this article, we'll explain what it means when a pool "floats," why it happens, and how builders work to avoid it.
What Does It Mean When a Concrete Pool Floats?
When homeowners hear the term "floating pool," they often picture a pool drifting around like a boat.
That's not what actually happens.
A floating pool is a pool shell that has been pushed upward by groundwater beneath it. In some cases, the pool may partially lift out of the ground. In more severe situations, it can rise enough to cause significant structural damage to the pool and surrounding deck.
Why Do Concrete Pools Float?
The primary cause of a pool floating is something called hydrostatic pressure.
Hydrostatic pressure is the force created by water pushing against a surface. When groundwater accumulates beneath a swimming pool, it creates upward pressure against the bottom of the structure.
Think of it like trying to hold an empty cooler underwater. The water beneath it is constantly trying to push it back to the surface.
The same principle applies to swimming pools.
If groundwater levels become high enough—often after periods of heavy rain, flooding, or in areas with naturally high water tables—the upward force beneath the pool can become substantial.
A pool that is full of water has significant weight helping hold it in place. However, when a pool is drained or partially drained, that downward force is reduced, making it more vulnerable to hydrostatic pressure.
If the upward pressure becomes greater than the forces holding the pool in place, the pool can lift.
How To Prevent Pool Floating
Because hydrostatic pressure is a known concern, pool builders take steps during construction to help manage groundwater and reduce the risk of floating.
Hydrostatic Relief Valves
Most concrete pools are built with hydrostatic relief valves installed in the floor of the pool.
These valves are designed to relieve groundwater pressure by allowing water to enter the pool rather than build up beneath it. This helps reduce the upward force acting on the pool shell.
Drainage and Site Conditions
Proper drainage is another important part of preventing hydrostatic pressure problems.
Depending on the property, builders may incorporate drainage systems designed to direct water away from the pool structure. Understanding local soil conditions and groundwater levels is also an important part of the planning process.
An experienced builder will evaluate these factors before construction begins to help ensure the pool performs as intended over the long term.
What Happens When a Concrete Pool Floats?
When a concrete pool lifts out of the ground, the results can be dramatic.
The pool shell may crack, plumbing lines can become damaged, and surrounding decking may shift or break as the structure moves.
The photos below show examples of concrete pools that have experienced hydrostatic pressure issues and lifted from the ground.
While these situations are uncommon, they demonstrate the power groundwater can exert beneath a pool structure.
It's also important to understand that hydrostatic pressure is not unique to concrete pools. Any vessel installed below ground can be affected by groundwater pressure if conditions are severe enough.
The Bottom line
Yes, Concrete (gunite) pools can float.
Fortunately, builders have long understood this challenge and typically use construction practices to help prevent it.
If you're researching inground pools, understanding how groundwater affects pool structures is just one of many factors worth considering before making your decision.
Frequently Asked Questions
How Do You Prevent a Concrete Pool From Floating?
Pool builders use several methods to help prevent a concrete pool from floating. Common strategies include installing hydrostatic relief valves, designing proper drainage systems, and evaluating groundwater conditions before construction begins. These measures help relieve pressure beneath the pool and reduce the risk of the structure lifting out of the ground.
Do all concrete pools have hydrostatic relief valves?
Most modern concrete pools are built with hydrostatic relief valves to help manage groundwater pressure. However, the exact design and construction methods can vary by builder and location.
Can a pool float if it is full of water?
It is much less likely. The weight of the water inside the pool helps counteract the upward force created by groundwater pressure. Floating is more commonly associated with pools that have been drained or partially drained when groundwater levels are high.
What is hydrostatic pressure?
Hydrostatic pressure is the force created by water pushing against a surface. In the case of swimming pools, groundwater beneath the pool can create upward pressure against the pool shell. If that pressure becomes strong enough, it can cause the pool to lift out of the ground.
Can fiberglass pools float too?
Any inground pool can be affected by hydrostatic pressure under the right conditions. However, a properly installed fiberglass pool that remains full of water is highly unlikely to float. Problems are most often associated with pools that have been improperly drained or installed.
From the Author
If you've been researching concrete pools, you've probably come across stories or photos of pools that have literally lifted out of the ground. It's one of those topics that can sound almost impossible until you realize there's actually some science behind it.
I'm Marcus Sheridan, co-founder of River Pools Virginia, and for more than 20 years I've helped homeowners research and compare inground pool options. I've had many conversations about hydrostatic pressure, groundwater conditions, and the misconceptions surrounding pool floating.
My goal with this article is to give you a straightforward understanding of what's happening beneath the concrete pool surface so you can make informed decisions as you research your pool options.
From the Manufacturer
At River Pools, we regularly help homeowners compare different inground pool options and better understand the factors that can affect a pool's long-term performance.
Whether you're evaluating a concrete pool, fiberglass pool, or another type of inground pool, understanding how things like construction methods and site conditions can impact your investment is an important part of the decision-making process.
If you're considering an inground pool and want to discuss your project with a trusted independent installer in your area, the next step is starting that conversation.
Ready to start the conversation?
