From Sidlow the Mole turns north west towards Brockham. A number of minor tributaries join the river from the west and are typically second order streams draining the woodland and arable land between Horsham and Dorking. The 18th-century weir at Betchworth was modified in 2004 to facilitate the installation of two 27.5 kW low-head hydro turbines. About 90% of the energy generated is fed into the regional electricity grid, while the remainder is used to supply the Betchworth Park Estate, where the weir is situated. The river leaves the Weald Clay at Brockham, passing Betchworth Castle and flowing briefly across greensand and Gault Clay to Pixham, north east of Dorking. A mean flow of is measured at a fourth gauging station, located at Castle Mill ( above OD). At Pixham the Mole meets the Pipp Brook, a tributary draining the northeastern slopes of Leith Hill.