That white crust on your faucets - it's your water.

Two easy routes. Your water supplier publishes the hardness for your area on their website, usually free and searchable by postcode – that's the quickest. Or buy a home test kit, which takes a couple of minutes and gives you a figure for your own tap. Having the number is what tells you whether this is a wiping problem or worth treating at source.

Only in the shower, and only partly – they're aimed more at how water feels on skin and hair than at removing hardness minerals. They do nothing for the taps, the toilet or the bath, which are on the same supply but a different outlet. Think of one as a comfort improvement rather than a descaling solution.

It depends on how hard your water actually is, how long you'll be in the house, and what a fitted system costs where you live – which is why the number comes first. Softeners do reduce scale substantially, and there's a real case for them in very hard water areas. Get a quote or two before deciding; prices and water hardness both vary enormously by region.

Anything that screws on and comes off again – a showerhead filter, a jug or countertop filter for drinking water – plus a regular descaling routine. A plumbed‑in softener isn't a tenant's decision; if the scale is bad enough to be damaging fixtures, that's worth raising with the landlord rather than paying for yourself.

The evidence for these is weak and inconsistent, and independent testing has generally not supported the claims made for them. If you're spending money on treatment, the established options are ion‑exchange softeners and, to a lesser extent, salt‑free conditioners. A clip‑on device at a low price promising the same result is worth being sceptical about.