Installing a Reverse Osmosis water filter system

For a couple of years now we have been drinking filtered water at home. We started off with a jug system when we decided the strong whiff of chlorine from water straight out of the tap was too unpleasant to ignore. But filter jugs are fiddly, clutter the kitchen, and are expensive in replacement cartridges.

So we fitted an under-sink filter and separate drinking water tap. Actually, we sited the filter housing in the cellar beneath the kitchen, where there is more room. The system worked very well, producing plenty of pleasant odour-free water. The cartridge needed changing every six months, but apart from that five minute job it just sat there, doing its thing.

The cartridges were an all-in-one combination of a polypropylene sediment filter and granulated active carbon. Unfortunately, Screwfix have stopped selling them and they are no longer widely available. I have been told that other ten-inch filters can be substituted, but I have not tried them. They all seem to do just one job and I think they are intended to be used in more elaborate systems with multiple housings.

For this and other reasons we have decided to retire our old filter and move to a new Reverse Osmosis (RO) system. This is like upgrading from a pedal cycle to a car, in that they both do the same basic job but one is much more complicated.

For a start, the RO system is mains powered and microprocessor controlled. It has a pump, sensors and solenoid valves, and an electronic display panel. There is a pressurised water storage vessel too. Instead of the single canister containing one combination filter, our new RO system has four separate filters – plus the reverse osmosis membrane which is the heart of the system. It also produces waste water which must be plumbed away.

All this equipment takes up a fair bit of room and I was glad not to have to install it under the sink. It also saved some time having already installed the drinking water tap in the kitchen worktop and the mains water feed pipe. All the pipework is flexible plastic ¼ inch tubing, and the fittings are all push-fit except for the tap and waste fitting which are compression.

What am I doing talking about inches in the 21st century? Well, UK plumbing went virtually 100% metric ages ago but the water filter industry is geared to the huge US market. Hence we are obliged to talk about 10 inch filters and ¼ inch plumbing.

What’s involved in installing it? First, you have to put two screws in the wall, on which the main chassis hangs. Next to this sits the steel storage vessel. In our case this needed to be on a shelf, and I had to make sure it could support the weight of more than 10 litres of water when full. In a kitchen cupboard it could be on the floor, and weight shouldn’t be a problem. It has to be within easy reach of a mains power outlet. In our case, this meant feeding the cable up through a hole in the floor to the socket for the dishwasher.