The HydroPro™ hydrostatic pressure relief valve sits inside the pool shell, in the deepest point, and does absolutely nothing for the entire life of your pool — unless the groundwater under the pool ever rises above the water level inside it.
Then it works out to be the most important $0-line-item on your quote.
What actually goes wrong without one
A fibreglass pool full of water weighs a lot. When the ground beneath it is dry — the normal state — the water pressure inside the pool pushes down on the shell and everything stays put.
Now imagine what happens after a Mackay wet season delivers 400mm of rain in a fortnight. The water table under coastal Mackay — already sitting only a metre or two below the surface in suburbs like Slade Point, East Mackay, Illawong, Bucasia and Blacks Beach — rises. The soil around and under the pool becomes saturated. Suddenly there’s more upward water pressure from below the shell than downward water pressure from the pool water inside it.
If the pool is empty at the time — cleaned for a top-to-bottom scrub, for instance — the buoyancy pushes the empty shell upward like a boat hull. Cracked shells, popped waterlines, and shell displacement have all happened to non-HydroPro pools in coastal Queensland after big wet seasons.
What HydroPro™ does
HydroPro™ is a small one-way relief valve moulded into the deepest point of the shell. If the pressure below the pool ever exceeds the pressure above, the valve opens and lets a small volume of groundwater into the pool shell itself, equalising the pressure and stopping the shell from lifting.
You’d never notice it happen. The pool water becomes slightly cloudy for a day or two if the valve opens; you shock the pool once and it clears. But the shell is protected from the buoyancy event that would otherwise crack it.
Why it matters more in Mackay than most of Australia
Two reasons.
The water table is high. Coastal Mackay sits on old alluvial floodplains — the Pioneer River deposited that soil for a hundred thousand years. Groundwater sits close to the surface in Mackay’s coastal suburbs, and after cyclone season it rises fast.
Rain events are extreme. A one-in-ten wet season in Mackay drops half a metre of rain in weeks. That’s the exact scenario that saturates the ground under a pool and creates the buoyancy problem.
Inland regions with rocky soil, low water tables and slow-drying rain events — much of the Isaac Region, for example — face this risk far less often. But every Compass pool ships with HydroPro™ as standard because the manufacturer would rather warrant every install than exclude some.
The lifetime hydrostatic warranty
This is the part most families don’t realise. Compass is the only Australian fibreglass pool manufacturer that covers hydrostatic damage under warranty for the life of the shell. Every other brand explicitly excludes it — because they can’t guarantee the pool won’t float in an extreme rain event.
Home insurance, by the way, also excludes it. Actions of “groundwater” or “rising water” sit under nearly every home policy’s ground-movement exclusion. If a non-Compass fibreglass pool cracks after a big wet season in Mackay, it’s the owner’s problem, not the insurer’s.
What we tell families at the site visit
If you’re building anywhere on coastal Mackay — anywhere the ground is soft, the block is flat, or you can see water pooling after a shower — HydroPro™ is genuinely doing structural work on your pool. It’s not a marketing feature.
Every quote we write includes it. Every install we’ve done in the Mackay region since we started has one. And in the years we’ve been installing, we haven’t had a single hydrostatic-related shell claim.
Book a site visit and we’ll show you where the valve sits on the shape you’re considering and what the drainage plan looks like for your specific block.
