Coogee’s Steep Streets: What the Hills Do to Drainage and Water Pressuare

It’s a clear fact to anyone who has walked along the path from Coogee Beach that there is a definite tilt in the suburb. It rises up from the sand quite abruptly, the coast is predominantly cliffs falling down towards the bay and Arden Street is one of the steepest streets in Sydney. It is that dramatic landscape that provides Coogee with its views of the ocean and its character. It also has a real effect on the flow of water through the suburb’s plumbing system in ways which can be very surprising to residents.

What slope does to drainage

Drainage relies on gravity and proper fall. That cuts both ways on Coogee’s hilly streets. When pipes are laid on the slope, water flows rapidly; sometimes even too rapidly, causing solids to remain behind and gradually forming blockages. When a drain must be laid across a steep site, it is actually quite difficult to achieve a steady fall. A slightly out-of-level section can lead to a flat spot or a sag where waste accumulates and blocks in the same place, over and over again.

The steep ground also moves. Slopes settle and shift over many years and these movements put tension on buried pipes, causing joints to crack in older clay or earthenware drains. After a joint cracks on a hillside, debris snags on the rough break and causes blockages, and stormwater infiltrates. Which leads to the larger problem on the slopes of Coogee: runoff.

Stormwater runoff on a hill

In a steeply sloping neighbourhood, heavy rainfall cascades down the hill rapidly and increases as it goes. Properties lower on the slope, and there are a lot of them from the ridge down to the beach, can get a massive amount of run-off that exceeds stormwater drains, particularly if a portion of the drains is clogged with leaves and debris washed down from above. The end result is water backed up against buildings, in basements and garages.

What slope does to water pressure

All that height comes with pressure. In any hilly suburb, the pressure of the mains water supply changes according to elevation; properties at the base will receive more mains water pressure than properties at the top. Excessive water pressure and low water pressure are not desirable in plumbing.

Persistently high pressure stresses pipes, fittings and flexi hoses, reducing their life and increasing the chances of a sudden burst, this is often overcome by the installation of a pressure-limiting valve and many older Coogee properties don’t have one. Low pressure up the hill, on the other hand, manifests itself as weak flow and weak hot water, and may disguise other issues. If the pressure feels like it’s too high or too low, it’s better to get it checked than put up with it.

The signs worth watching on a Coogee slope

• A blocked drain in the same location. When it is on a steep site, it generally implies that there is a sag, a flat area, or a cracked joint where the ground has shifted.
• After rain, pooling of runoff against the building. A sign that stormwater drainage is inadequate to meet the rate of flow down the hill.
• Water coming up through the floor in a lower-level garage or basement. Common in heavy rain on the downhill side of steep blocks.
• Banging pipes or frequent flexi hose issues. Signs that there could be too much pressure on the plumbing.
• Weak flow up the hill. Typically elevation related, but worth diagnosing in case something else is going on.

When it turns into an emergency

Most plumbing problems relating to sloping areas develop very slowly, but heavy rainfall can make them an emergency fast. The living space in a garage or home on a steep block could be flooded in just a few minutes during a Sydney thunderstorm when the stormwater system becomes blocked, as there is a whole hillside feeding the system. And a pipe that is under pressure can burst at any moment. If the water is overwhelming you, shut it off wherever possible and call in a licensed plumber, our team of emergency plumbing professionals in Coogee and surrounding Rose Bay in the Eastern Suburbs regularly encounters drainage and pressure issues in steep suburbs.

The bottom line

Coogee’s hills are what give it those ocean views, and why its plumbing is required to function a bit harder. Steep ground races stormwater downhill, makes consistent drainage fall harder to maintain, stresses pipes through ground movement, and swings water pressure with elevation. When drainage continues to be a problem in one spot, or water puddles where it shouldn’t, the terrain is usually part of the story. Getting a proper look at what’s happening, ideally with a camera in the drain, beats battling the same issue every wet season.