Whole House Water Filter Installation Guide: Step-by-Step for 2026

Tools and Materials the Job Requires

For copper pipe: pipe cutter (rotary type, not hacksaw — produces a cleaner cut), pipe deburring tool or half-round file, two 1" BSP compression fittings or push-fit connectors (depending on your pipe-to-filter connection method), PTFE thread tape, adjustable spanner or 30mm open-end spanner. For plastic (PEX or MDPE) pipe: pipe cutter appropriate for plastic, push-fit or compression fittings rated for your pipe diameter.

The installation also requires a bypass valve assembly — this lets the filter be isolated for maintenance without shutting off the whole house. Mam Nature can provide you a bypass in the needed size on optional request. Alternatively, a three-valve bypass from a plumbing supplier can be used as well.

Optional but useful: bucket and towels for residual water in the pipe after shutoff, pipe-clips and screws for securing the housing bracket to the wall, spirit level to ensure the housing hangs vertically (gravity helps cartridge seating). Please see as well our tools needed video.

Choosing the Right Installation Location

The filter must install on the cold mains supply line after the water meter and the stop cock (main shutoff valve) and before the first branch to any tap, toilet, boiler, or appliance. This ensures 100% of household water passes through the water treatment system.

Choose a location that is accessible — you will be returning annually to swap the cartridge. The housing needs roughly 30cm of clearance below it to unscrew the below part of the filter housing. Avoid locations subject to freezing (uninsulated garages, external walls without insulation) — most residential filter cartridges are not rated for sub-zero temperatures.

If your system includes a Particle Filter (Essential Plus, Complete Set, Complete Set Plus), the particle filter installs upstream (before) the fine filter cartridge. The Water LIME (Complete Set, Complete Set Plus) installs upstream of both. Refer to the product's installation guide for the specific sequence, which follows: Water LIME → Particle Filter → Fine Filter → Dynamizer (if included).

Step 1 — Shut Off the Water Supply

Locate your main stop cock — usually under the kitchen sink, in a utility room, or near the water meter. Turn it fully clockwise to close. Open a cold tap downstream to confirm the supply is off and to release pressure in the pipes.

Once the tap runs dry, you have successfully depressurised the section you will be working on. Leave the tap open while you work — it confirms pressure has not built up unexpectedly and allows air into the pipe to drain residual water.

Step 2 — Mark and Cut the Pipe

Measure and mark the section of pipe to be removed. The housing needs the length of the bypass valve assembly plus the housing connection fittings — typically 250–350mm of pipe is removed. Check your bypass kit's dimensions before cutting.

Use a rotary pipe cutter for clean, square cuts on copper. Two cuts are needed — one on each side of the section to be removed. Have a bucket ready: residual water in the pipe will drain out once cut. Deburr the cut ends with a file or deburring tool to ensure fittings seat correctly.

Step 3 — Fit the Bypass Valve and Housing

Connect the bypass valve assembly to the cut pipe ends using your chosen fittings (compression or push-fit). Wrap the BSP threads on the filter inlet/outlet ports with PTFE tape (3–5 turns clockwise as viewed from the thread end) before connecting to the bypass ports.

Mount the housing bracket on the wall. The housing hangs vertically from the bracket — ensure it is level. Hand-tighten the clamp of the Fine Filter housing — do not use a spanner to tighten; overtightening damages the thread and O-ring.

Connect the bypass valve ports to the filter housing inlet and outlet. Ensure the inlet (water in) connects to the correct port — the housing is typically marked with flow direction arrows.

Step 4 — Commission the System

Close the bypass valve isolator handles (so water is diverted through the filter). Slowly open the main stop cock — quarter turn, pause, check for leaks, quarter turn further. Do not open fully in one movement; a sudden pressure surge can unseat fittings before they have had a chance to establish a water-tight seal under pressure.

Check every connection point for drips. A torch helps. Run your hand around each fitting. Small weeps at compression fittings can often be resolved with a quarter-turn of the spanner. If a push-fit fitting leaks, shut off, pull the fitting, inspect the pipe end (must be square, clean, and fully inserted), and reseat.

Once the system holds pressure without leaks, open a cold tap at the furthest point from the filter and flush for five minutes. The first water through a new cartridge may contain fine particles from the manufacturing process — these are harmless but should be flushed before drinking. The water will run clear within a few minutes.

Annual Cartridge Replacement

The replacement procedure reverses installation at the housing only — the bypass valve and pipe connections are permanent. Shut the bypass valve (divert water around the Fine Filter to maintain water provision to the house during the replacement procedure), open a downstream tap to release pressure, unscrew the clamp of the bottom part of the Fine Filter housing by hand (anti-clockwise to loosen when viewed from below), pull the old cartridge, insert the new one, position the bottom part of the housing with the clamp, tighten the clamp (clockwise), re-open the bypass, check for leaks, flush five minutes. The whole procedure takes ten minutes and interacts only with the bottom part of the Fine Filter housing — the upper part of the Fine Filter housing and the bypass valve stay in place.

Set a calendar reminder for 12 months from installation. If you notice flow reduction, taste change, or visible turbidity before 12 months, replace the cartridge early — these are signs of saturation.