The filtration in both the MS-MZ water filter and the Family Water Filter is performed by hollow fibre membranes. These are small tubes in which water flows both through their centres and through their porous walls. The porous walls have very small holes, 0.00002 millimeters in diameter, which allow water to pass, but hold back bacteria and viruses. Both water filters have mesh pre-filters to hold back larger particles of dirt as well as main filters of hollow fibre membranes.
When the Family Water Filter’s integrated hand pump is operated, dirty water is drawn up through the centres of the fibre membranes and back down again, continually washing out the fibres, while clean water comes through the walls to the outlets. The MS-MZ Water Filter is operated by gravitational force thus no need for manual hand pump. In addition; the filters have systems to flush clean water in reverse, back through the walls to clean them out. This takes away the accumulated substances removed from the water.
The MS-MZ Water Filter is maintained by carrying out the backwash operation. The manual hand pump also requires greasing when it gets hard to rotate due to rust incase of metallic pumps, that we prefer as they are long lasting compared to the plastic ones.
Family Water Filter pump‟s seal is the only part that wears. Its life is increased by applying grease which is stored in a grease pot within the casing of the filter. Spare seals are stored on the piston rod (or in the case of the Mark 2 Family Water Filter, in the pump handle) and are easily accessed if the seal needs changing.
The Family Water Filter requires a small amount of maintenance to ensure its continued successful operation. Where the source is muddy water, the filter will need to be back-flushed daily or several times a day to remove large particles and keep it functioning effectively. We train community members throughout Kenya to look after each filter.
A mesh pre-filter protects the membrane by removing larger particles of dirt. The pre-filter can be removed and cleaned when necessary.
The very small particles are removed from the membranes through back flushing whenever necessary, depending on the amount of water being pumped.
Water filters hollow membranes are designed to be chemically cleaned in the event of internal bio-film growth. Each Family water filter comes with NaDCC tablets stored in a built in reservoir while the MS-MZ Water Filter is chemically cleaned using the locally available sodium hydroxide, sodium hypochlorite and formaldehyde when necessary. This chemical cleaning restores the flow rate.