Rain water is acidic with pH of unpolluted water ranging from 5.0 to 5.5 compared to neutral water of 7.0. Rain from thunderstorms is even more acidic with a pH typically less than 4.0 and in extreme storms can be as low as 2.0. A pH booster filter is designed to increase the pH of rain water to bring it closer to 7.0.
Acidic rain water will reduce the life of your hot water storage tank, copper pipes and metal fittings that come into contact with your hot water as it is corrosive at 5.0-5.5 and more so if the pH is less than this. The ideal pH for water is between 6.5 and 8.5 and you will find that many of your appliances have warranty conditions requiring pH to be within 6.5 and 8.5.
If you are planning to use rain water for your water supply, Siddons Solar Hydronics recommends that you install a pH booster filter such as the Clarence pH booster filter which has cartridge of dolomitic calcite limestone granules sized between 0.6 - 1.2 mm. The pH booster filter works by slowly dissolving the calcium magnesium carbonate contained in the dolomite granules to raise the pH which reduces the potential leaching of copper, lead and other metals found in typical plumbing systems.
The dimensions of the filter cartridge are 510mm x 110mm with 16 / 40 screened mesh that allows good water flow through the dolomite granules, which are sized between 0.6 - 1.2 mm. Refillable cartridges can be purchased and are easily replaced by unscrewing the filter cap, removing the spent cartridge and reinserting the new cartridge. The filter cartridge is housed in a big blue 20inch filter housing with 25mm/1inch female BSP inlet & outlets. The outside dimensions of the filter housing are 610mm x 185mm diameter without the mounting bracket.
The Clarence pH booster filter is suitable for water flow of up to 170 litres per minute using a pressure limiting valve set to 500kPa, which is the ideal inlet water pressure. The maximum water pressure should be no more than 620 kPa.