Installing a Reverse Osmosis water filter system

The waste water pipe normally goes to a saddle clamp you have to put around the waste pipe from the kitchen sink, after having drilled a ¼ inch hole in it. I was a bit reluctant to do so, mainly because I was installing in the cellar, quite a bit lower than usual. The system would have to push the waste water against gravity, and I was also worried that waste water from the sink might contaminate the RO system. I opted instead to feed the waste pipe down and out through the cellar door frame to the rainwater grid outside. It remains to be seen whether this solution produces its own set of problems such as freezing in winter, or creepy-crawlies.

I connected up the original mains feed pipe (if you were installing from scratch, you would use a self-piercing clamp valve to tap into the mains cold water feed), then connected the pipe to the outlet tap and then the one to the pressure vessel.

The next stage was to unwrap and install the first three filters in their respective canisters. These screw into three heads mounted on the underside of the chassis. The polypropylene (PP) sediment one has a transparent housing for visual inspection. Next is the granulated active carbon (GAC) filter and then there is a carbon block (CTO) filter. It’s quite fiddly making sure the sealing rings are correctly seated in the top of the heads, as they kept falling out. With hindsight, it might be possible to turn the whole unit upside down and fit them with gravity on your side.

The water from these three filters flows to the RO membrane but first, when installing you have to disconnect the pipe here and flush them through into a bucket. This gets rid of carbon ‘fines’ which would otherwise contaminate the RO membrane. After several bucketfulls passed through, I was satisfied that the water was running clear. A couple of the filter housings leaked and I had to really tighten them hard with the special large plastic spanner supplied.

The RO membrane is rolled up with rubber seals at either end, and packaged in a preservative solution. The seals have to be lubricated (with Vaseline some say, but others advise against this so I used a drop of silicone lubricant) and then the membrane goes into its own chamber at the rear of the unit. I read – too late – that you should avoid touching it with bare hands to minimise the risk of bacterial contamination. The fifth filter is a T33 taste enhancing filter which comes pre-installed.