Forrestfield Water Hardness & Quality Report (2026)

Forrestfield's drinking water is supplied by the Water Corporation via the Integrated Water Supply Scheme (IWSS), with a dominant groundwater proportion incorporating local Darling Range foothill aquifer components for the City of Kalamunda LGA eastern Perth hills distribution in Western Australia. Water hardness in Forrestfield is measured at 238 mg/L — classified as very hard, exceeding the Australian Drinking Water Guidelines (ADWG) aesthetic guideline of 200 mg/L published by NHMRC. Forrestfield — a large outer eastern Perth suburb in the Kalamunda LGA at the base of the Darling Range, known for the Forrestfield industrial estate, the High Wycombe residential growth corridor, and the eastern Perth Hills gateway to the Perth Hills National Parks — carries very hard supply from the highly mineralised eastern Perth foothill groundwater distribution blend.

Forrestfield's elevated hardness reflects the dominant groundwater proportion in the outer eastern Kalamunda IWSS distribution, drawing from the Tamala Limestone superficial aquifer system and local Darling Range foothill weathered granite and ironstone aquifers that accumulate significant dissolved minerals through the lateritic soil profile. The Forrestfield outer eastern Perth hills distribution at 238 mg/L and TDS 701.5 mg/L is among the hardest inner eastern Perth sub-zones recorded, significantly harder than the softer inner Perth desalinated-blended zones and harder than Armadale (166.5 mg/L) to the south.

Forrestfield residents face significant daily limescale challenges — kettle descaling every one to two weeks is common, shower screens accumulate heavy deposits, and hot water system elements require annual inspection. Solar hot water systems in WA's climate need regular servicing. Under WA water restrictions, garden irrigation is limited to two days per week. The elevated lead reading (0.005 mg/L) warrants always briefly running the cold tap before drinking. The Water Corporation provides water quality information at watercorporation.com.au, with all ADWG health standards met.