A stormwater pit with a submersible pump is one of the most effective and reliable drainage solutions available for Sydney properties that flood regularly due to low-lying topography or inadequate gravity drainage. Understanding how a stormwater pit works and why it prevents flooding helps property owners appreciate why it is recommended for certain sites and what to expect from the system once installed.
How a Stormwater Pit Works
Collection
A stormwater pit is a below-ground chamber — typically made from concrete, polyethylene, or fibreglass — installed at the lowest point of the property where water naturally concentrates. Surface drains, sub-surface drains, and downpipe connections all direct water into the pit through inlet pipes. As water enters the pit during a rain event, it accumulates in the chamber. The pit is sized based on the peak inflow rate expected from the property’s roof area and paved surfaces during a design rain event. A licensed blocked drain plumber in Sydney will calculate the required pit capacity based on the property’s catchment area. Related: What Does a Stormwater Pipe Do?
Automatic Pump Activation
Inside the pit, a submersible pump is mounted at a level that keeps it submerged when the pit is operating. A float switch attached to the pump detects when the water level in the pit rises to the activation point. When the float rises to the set level, the pump activates automatically and begins pumping water from the pit up through a discharge pipe to the stormwater outlet — typically the street kerb or a council stormwater pit. The pump continues running until the water level drops to the deactivation point, at which point the float switch cuts power to the pump. This cycle repeats automatically throughout a rain event without any manual intervention.
Discharge
The discharge pipe carries pumped water from the pit to the approved outlet. The pump must be sized to overcome the difference in height between the pit and the discharge point — the “head height” — as well as any friction losses in the pipe. A correctly specified pump will discharge water at a rate sufficient to keep pace with the peak inflow from the property during heavy rain, preventing the pit from overflowing and the property from flooding. A licensed Sydney plumber will specify the pump output, the discharge pipe diameter, and the pipe route as part of the system design.
Why a Stormwater Pit Prevents Flooding That Gravity Drainage Cannot
Gravity drainage relies on water having a downhill path to an outlet. On low-lying properties where the yard, driveway, or below-ground area sits lower than the available stormwater outlet, no gravity-based drainage system can remove water — it simply has nowhere to go by gravity. A stormwater pit with a pump overcomes this physical limitation by mechanically lifting the water to the outlet. This makes it the only viable permanent drainage solution for properties where flooding would otherwise be unavoidable. See also: 7 Plumbing Emergencies That Cannot Wait.
Maintenance of a Stormwater Pit System
A stormwater pit and pump system requires periodic maintenance to perform reliably over its service life. The pit chamber should be cleaned of accumulated sediment annually. The pump should be inspected annually and the float switch tested to confirm it activates correctly. The discharge pipe and non-return valve should be checked for blockages or fouling. A licensed commercial plumber in Sydney can carry out an annual service inspection and replace the pump when it reaches the end of its service life — typically every eight to twelve years depending on usage frequency. Related: How Much Does Emergency Plumbing Cost in Sydney?
If You Need a Stormwater Pit Installed in Sydney, Call 1300 071 280
All Day Plumbing designs and installs stormwater pit and pump systems for residential and commercial properties across Sydney. If you need help preventing flooding on your Sydney property, call us on 1300 071 280. We offer site assessments, upfront pricing, and professional installation with systems correctly sized for your property’s catchment area and available head height.