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How to install a Reverse Osmosis Water Filter

This tutorial explains the process of fitting  reverse osmosis system, including tips on how to drill through your sink and how to install the various components found in a RO System.


Pre Installation Notes

**Please note that this tutorial is written for systems that use ‘push fit’ fittings. With this type of fitting make sure that you push them in firmly to ensure that the tube has been pushed completely in, you should feel them slide into place if done correctly.

Firstly ensure you have a suitable site for the system, and make sure the system will fit in the chosen site. This will be somewhere with a cold standard sized copper mains water pipe and a nearby 35mm standard sized waste pipe –  (the type that sinks use for drainage as standard). Usually beneath the sink where the water filter tap will be mounted is the ideal place; however in situations where there is not enough room for the system itself beneath the sink it can be installed in a neighbouring cupboard and the pipes can be run through the side panel of the cupboard to where they need to go.

For pumped units ensure you also have an electrical plug socket nearby or run an extension lead to the cupboard as it will need to be plugged in the mains for the pump to operate.


Identifying the Components

With most Reverse Osmosis Water Filter Systems you will have some or all of the below components. This guide will explain how to fit all of these below:

RO water filter tap

RO Drinking Water Tap

Self Piercing saddle valve for reverse osmosis

Mains water Clamp















Inline ball Valve 1/4 inch

In-line Ball Valve

Reverse Osmosis Drain Clamp

Reverse Osmosis Drain Clamp













Step 1 – Fitting the Mains Clamp

See the components images above to identify the Self Piercing Mains clamp.

  1. Firstly hand-turn the self piecing screw head on the top of the clamp until the piecing pin has completely retracted into the roof of the clamp and cannot be felt. – This is important or it will prematurely piece the pipe when securing the clamp.
  2. Find a suitable pipe for the clamp to latch onto; this should be a standard sized copper cold water mains pipe (such as the one that runs to the cold tap). Ensure that the pipe is the cold water pipe as the water filter system will not work with hot water.
  3. Put the clamp around the pipe and slide the metal cradle between the clamp and the pipe. For this the widest arch side of the cradle should be the side that is in contact with the pipe.
  4. Tighten the bolt at the bottom of the clamp with a spanner (not the top self piercing screw head) until it is tightly secured to the mains pipe.
  5. Push a short length of ¼” pipe into the push fit connector on the Self Piercing Mains clamp
  6. Attach a ¼ inline Valve (as seen in pic 2) onto the end of this short piece of pipe and ensure it is in the off position. This will be the shut off valve for the system if it is ever moved or needs servicing.
  7. Hand-turn the self piecing screw head on the top of the clamp until it will turn no further and has completely pierced the mains pipe.
  8. Opening the self piecing screw head on the top of the clamp, you will see the short length of pipe go stiff and the push fit socket on the clamp will drip, keep moving the pipe around until this stops (as outlined in the above note).

Note: at the last stage above (after opening the self piecing screw head on the top of the clamp) the clamp will always leak from the push fit connector socket on the clamp, this is normal, keep pushing and pulling the pipe where it goes into the clamp and moving it from side to side until it stops dripping. This is normal and it will stop dripping


Step 2 – Fitting the Waste Clamp (RO systems only)

See  the components sheet to identify the waste clamp

  1. Take the one sided sticky foam from the bag with the waste clamp in, take out the circular centre piece of the foam and stick it to the inside of the clamp half with the hole in so that the holes align.
  2. Put the clamp around the waste pipe on a straight section of the pipe (not a U-Bend) and tighten the bolts (the quickest way is to hold the nuts by hand and use a screwdriver on the bolts), ensure that the hole for the push fit connector is in an accessible position for drilling through the push fit hole and into the waste pipe
  3. Find a drill piece that will fit through the push fit connector socket on the waste clamp, and drill through it into the waste pipe.
  4. If the push fit connector falls out of the socket, or the rubber gasket inside it falls out of the socket while drilling ensure that they are put back in place inside the push fit connector socket, otherwise it may leak later when the water filter system is running.


Step 3 – Fitting the Tap

See the components sheet to identify the Drinking Water Tap

Note: if you have a 3 Way Tap you can skip this step
  1. Find a suitable place for the tap to be mounted; usually they will fit on the corner of a sink. You will need to ensure that where the tap is mounted there will be enough room underneath the sink for you to use a box spanner to tighten the bolt on the taps screw stem to secure it to the sink itself
  2. Alternatively, if there is not enough room to mount the tap to the sink you can drill through the worktop itself by the edge of the sink, again ensuring there is enough room underneath to tighten the taps bolt.

 Note: if you have a granite worktop and need to drill through it as you cannot fit the tap onto the sink you will need to use specialist drill pieces and techniques for granite drilling. Alternatively you may wish to replace your normal hot/cold tap with a 3 way tap

Note: if your sink is not metal (i.e. is made of a china type material) then do not drill through it (it may crack)

Tips for drilling the hole on a sink: use metal drill bits and begin with a small one (about 2mm) and build up the hole using drill bits increasing in size by 1mm each time. You should finish by using a 12mm drill bit, drill the hole and carefully widen it a little by moving the drill around until the stem for the tap will fit into the hole.

  1. Put the smallest rubber gasket that comes with the tap onto the sink top hole, and put the tap stem through this.
  2. On the underside of the sink, first put the larger rubber gasket and then the metal one around the screw stem of the tap
  3. Put the bolt on the screw stem and tighten the bolt until the tap is securely fixed in the desired position/angle on the sink.
  4. Then push a piece of ¼” pipe into the push-fit fitting inside the bottom part of the taps screw stem


Step 4 – Connecting the System

  1. Attach a piece of ¼” pipe to the ¼” inline Valve that comes from the mains water clamp which was fitted in step 1. Cut to a suitable length and attach the other end to the rear of the system to the push-fit connector labelled “FEED WATER”.
  2. Attach a piece of ¼” pipe to the push-fit connector on the waste clamp. Cut to a suitable length and attach the other end to the rear of the system push-fit connector labelled “DRAIN WATER”
  3. Attach a piece of ¼” pipe from the push-fit connector on the tap stem to the rear of the system push-fit connector labelled “FAUCET”

Connecting the Tank – (if your Reverse Osmosis Water Filter System does use a tank)– Wrap lots of PTFE tape around the screw thread on the top of the tank and screw on the tank valve. Lots of PTFE tape should make this tight to screw on and is essential to prevent leaks from the tank valve.

Connect a Length of ¼” water pipe from the ‘Storage Tank’ socket on the system to the tank valve, turn tank valve in ON position.

  1. Once all connections have been made, turn on the ¼” inline valve from the mains clamp, as well as the valves on the back of the system (“FAUCET” and “FEED WATER” valves)
  2. If the unit has a pump, plug in the power lead and turn on the socket.

Make sure the tap is turned off. Leave for 1hr and then turn on tap until tank is completely drained (until the water flow is a dribble). Repeat 3 times then the water is ready for drinking.

Thank you for reading How to Install a Reverse Osmosis Water Filter

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October 6, 2011 at 9:48 am
1 comment »
  • November 6, 2011 at 3:15 pmbarricas

    The article is very excellent.Let me learn a lot of knowledge.

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