How to install a shower filter

What you need

• PTFE thread tape, sometimes called plumber's tape or Teflon tape. A roll costs almost nothing and is the difference between a dry joint and a drip.
• A cloth, to grip a stiff head without scratching the finish.
• An adjustable wrench, only if the old head is seized. Most come off by hand.
• Nothing else. If a set of instructions calls for solder, sealant or a plumber, you are reading about a different device.

Step by step

1. Turn off the shower and let it drain. There is no need to shut off the supply at the valve.
2. Unscrew the existing head counter-clockwise. It should come off by hand; if it is seized, wrap a cloth around it and use a wrench gently to avoid marking the finish.
3. Clean the arm's threads. Old tape, scale and grit are the commonest cause of a leaking joint. Wipe them clean and pick off any remaining tape.
4. Wrap the arm threads with PTFE tape, three to four turns, in the same direction you will tighten — clockwise, looking at the end of the arm. Wrapping the wrong way unwinds the tape as you screw the fitting on.
5. Screw the filter on, hand-tight. These are plastic or thin-wall metal fittings; over-tightening cracks them, and the tape is what seals the joint rather than the force.
6. Tape the filter's outlet threads the same way, then refit your shower head on the far side.
7. Run the shower and watch both joints for thirty seconds. A drip means take it apart, re-tape and refit.
8. Write the date on the housing in marker. This is the step everybody skips and the one that keeps the filter working in month eight.

Handheld showers are slightly different

The filter goes between the shower arm and the hose mount, at the wall — not between the hose and the wand. Fitting it at the wand end hangs several ounces off the end of a flexible hose, strains the connection every time you pick the wand up, and makes the whole thing awkward to hold. Everything downstream of the wall fitting is filtered anyway, so there is no benefit to putting it further along. The full handheld guide.

Replacement shower heads

Identical process with one fewer joint: unscrew the old head, tape the arm, screw the new filtered head on. That is genuinely all of it. The only additional thing worth doing is keeping the old head somewhere safe — if you rent, it goes back on when you leave.

Check the clearance first, not after

An inline body adds two to four inches of projection from the wall. In a small enclosure with a low ceiling that drops the head toward head height, and on a handheld setup the bracket is already sticking out. Hold a tape measure up before ordering rather than after — this is the commonest reason a filter gets returned.

While you are up there

Descale the shower head. It is off in your hand, and a night in a bowl of white vinegar will clear the nozzles of the scale that has been quietly costing you flow. On a hard-water supply this recovers more pressure than any filter choice will, and it costs nothing. Why pressure drops.