What Is a Hydrostatic Valve and Why Your Pool Needs One
When you look at your pool, you probably think about the water chemistry, the filter, or the robot cleaner—not a tiny valve hiding at the bottom. But that small, often overlooked piece of equipment is one of the most important protections your pool has. It’s called a hydrostatic valve, and without it, your pool could face serious (and expensive) damage.
In this post, we’ll break down what it does, why it matters, and how to know if yours needs attention.
What Is a Hydrostatic Valve?
A hydrostatic relief valve—commonly found in the floor of concrete and fibreglass pools—is a safety device designed to protect your pool from groundwater pressure. It sits underneath or inside the main drain and automatically opens if underground water levels rise too high.
In simple terms:
➡️ It stops your pool from “popping” out of the ground.
➡️ It acts as a pressure release system for your pool shell.
When the groundwater level becomes higher than the water inside your pool, the pressure pushes up against the pool shell. If that pressure isn’t released, the pool can lift, crack, or in extreme cases, be forced out of the ground—especially when the pool is empty or low.
How Does a Hydrostatic Valve Work?
The valve is designed to open only when needed. Here’s what happens:
Groundwater builds up after heavy rain, floods or rising water tables.
The pressure underneath the pool increases.
The hydrostatic valve senses this pressure difference.
It opens and allows groundwater to flow into the pool, equalising the pressure.
Once the pressure drops, it closes again.
This automatic pressure management is what keeps your pool structure safe.
Why Your Pool Needs One
1. Prevents Pool Shell Damage
Without a hydrostatic valve, your pool is at risk of cracking, shifting or floating out of the ground during periods of high groundwater.
2. Essential During Draining or Repairs
Any time your pool is emptied—or even partially drained—the water inside no longer counteracts groundwater pressure.
A working valve is non-negotiable for safe draining.
3. Protects Against Weather Extremes
After storms or long periods of rain, the surrounding soil can become saturated. A functioning valve gives your pool the protection it needs during unpredictable weather.
4. Peace of Mind for Homeowners
A hydrostatic valve is a small, inexpensive part, but it protects one of the biggest investments on your property.
Signs Your Hydrostatic Valve May Need Attention
A failing or blocked valve can’t do its job. Look out for:
Unexplained water appearing in or around the main drain
Difficulty keeping the pool full (water level dropping)
Debris or calcium buildup around the drain
A valve that feels stuck, brittle or loose
Recent flooding or heavy rains followed by odd pool behaviour
If you notice any of these signs, it’s worth having your pool technician check the valve.
Can You Replace a Hydrostatic Valve Yourself?
While it may look simple, replacing a hydrostatic valve isn’t a DIY job. It usually requires:
Diving equipment or draining the pool
Special tools to remove the main drain cover
Knowledge of groundwater pressure risks
Proper sealing to ensure it operates correctly
Because the valve is such a critical safety component, it’s best left to a professional.
How We Can Help
During our services, we inspect the hydrostatic valve area to make sure everything looks as it should. If we suspect the valve is worn, stuck or damaged, we’ll recommend replacing it before it leads to bigger issues.
A small part can prevent thousands of dollars in structural repairs—so it’s always worth staying on top of.
Final Thoughts
Your hydrostatic valve might not be the most exciting part of your pool, but it’s definitely one of the most important. By protecting your pool from underground pressure, it helps ensure your pool stays safe, stable and long-lasting—no matter what the weather does.