Avarmi Filtered Shower Kit

If your current shower head unscrews from the hose by hand, this screws on in its place — no tools, no plumber. That covers most UK bathrooms: mixer showers, bar valves, and anything with a hand-held head on a flexible hose.

Two exceptions, and we would rather tell you now than take the return. It does not fit a ceiling-mounted or fixed rainfall head, because there is no hose to unscrew. And we don't recommend it on an electric shower — Mira, Triton, Gainsborough and the like — because those run at a deliberately low flow rate, and putting a cartridge in front of that leaves you with a dribble.

Not sure which you have? Go and unscrew your shower head. If it comes off in your hand, you're fine.

It catches the bits hard water leaves behind in your pipes: flakes of limescale that break loose, along with rust and grit. You'll see them in the cartridge.

What no shower head can do is soften the water itself. The calcium that leaves white marks on your screen and taps is dissolved in the water, and taking that out needs a water softener. We'd rather tell you now than have you find out later.

Unscrew your old shower head from the hose by hand, screw this one on until the washer seats, and run it for ten seconds to flush the cartridge. Five minutes, no tools, no plumber. If the old head is stiff with limescale, a tea towel for grip is the most you'll need.

Renting? Nothing gets drilled or replaced. Keep your old head in a drawer and swap it back when you move out.

Solids. Rust, scale flakes, grit and sediment that old pipework releases travel through dense PP fibre before the water reaches the nozzle plate, and stay in the fibre. Pull the cartridge out after a few weeks and whatever colour it has gone is what used to arrive with the water.

When the flow drops off or the fibre has gone from white to brown — in most homes that's four to eight weeks. Five cartridges come in the box, so the first year is largely covered. Changing one takes about twenty seconds and needs no tools.

There is no subscription. You buy more cartridges only when you need them.

Less water, moving faster. The nozzle plate sends your supply through smaller openings, so the flow rate drops while the speed goes up — which is why it feels stronger on your skin than the head it replaced, and why less water goes down the drain. The cartridge doesn't affect this at all until it's genuinely full. When it is, the flow falls off. That's your signal to swap it.