Pressure cleaning in Sutherland Shire and St George

At the 2021 Census, separate houses were 60.8 per cent of occupied dwellings in the Sutherland Shire and 51.6 per cent in the Georges River local government area, both under the 65.6 per cent for New South Wales.

Flats and apartments were 24.8 per cent in the Shire and 36.2 per cent in Georges River, against 21.7 per cent statewide. So strata common property is a real share of the work here, beside the house washes.

Sutherland Shire Council's stormwater management plans are named for the Hacking River, the Lower Georges River and the Woronora River. Council says stormwater is carried to a waterway, and that runoff from roads and roofs carries pollutants like litter, sediments, oils, fertilisers, detergents and bacteria.

It says stormwater and waterway assets are about a third of the total value of all council assets, and that stormwater problems on private property are the property owner's responsibility.

Georges River Council says backyard drains mostly lead to the stormwater system, which flows directly into creeks, rivers and the ocean. It names paint, oil, sediment and pesticides among the pollutants washed off roofs, gardens, driveways and roads.

It asks cafés to put wastewater into the sewer and not the stormwater drain, and tells residents not to wash sand, gravel or cement where runoff can reach a drain. The council's area takes in 38 kilometres of Georges River foreshore.

The nearest long record Bureau of Meteorology station we could read is at Sydney Airport, across Botany Bay from the Shire. It records a mean annual rainfall of 1096.7 millimetres, against 756.3 at Penrith Lakes. Relative humidity averages 69 per cent at 9am and 57 per cent at 3pm, a flatter day than the west, and July nights average a minimum of 7.5 degrees.

Steadier humidity through the day means shaded walls and paths do not dry out as sharply between morning and afternoon, which is the condition algae and mould like.