The kit includes 1 x 254mm 5 micron pre-filter (stage 1) and 1 x 254mm CTO carbon filter (stage 2) along with 1 x 50 GPD high rejection RO membrane (stage 3) and 1 x 254mm clear 620ml refillable DI vessel with Indicator colour change resin (stage 4). This RO unit is fitted with a back-wash valve and an auto shut-off valve as standard and is supplied with all the pipework along with instructions and fittings needed to plumb in and start producing RO water. The auto shut-off will stop all water flowing through the RO unit when fitted to a float valve or manual valve on the production side of the RO unit. Once the production water is switched off, the RO unit will shut down completely. This feature saves water by preventing the excess flow going to waste. The auto shut-off valve makes this a very versatile RO unit as it can be used manually or fully automatically with the use of a float valve. The back-wash valve allows for the periodic manual flushing of the membrane housing. This increases the life of the membrane and DI resin. This RO unit is easy to install and maintain and produces RO water of the highest quality. Replacement membranes and pre-filers along with carbon filters and mixed bed DI resins are readily available. This RO unit can be used without a Total Dissolved Solids (TDS) meter as it is supplied with mixed bed DI colour change resin. This resin will change from green to orange when exhausted thus indicating a rise in TDS.