The complete guide
Buying Guide
A hand held bidet takes its water from a supply that is already there: a flexible hose runs from an isolator valve up to your cistern, and this kit puts a T-junction in that line.
What you are actually buying
Four parts. A sprayer head, a hose, a valve and a bracket.
The head is 304 stainless steel at the nozzle. That grade is not a marketing detail, it is the usual specification for fittings that live in permanent contact with water, and it is the difference between a fitting that still looks like metal in three years and one that has started to flake where the plating met the plastic underneath.
The hose is braided steel. The valve body is brass, and it is a T-valve, which is the piece that does the real work: it goes in line between the supply and the cistern inlet so that the cistern still fills exactly as before, with the sprayer taking a branch off the same feed.
Installation
The kit connects to the flexible supply that already feeds your cistern: a T-valve sits in line before the cistern inlet, and the sprayer hangs on a bracket on the wall or over the cistern. Installation and backflow requirements vary by property. Follow the product instructions and your local water rules, and ask a qualified plumber if you are not sure your supply is suitable.
Setting the pressure
Do this once. Open the T-valve slowly with the sprayer pointed into the pan until the jet is firm but comfortable, then leave it. The trigger on the head is what you use day to day.
The valve also closes fully, and it is worth closing it if you are away for a while. A hose sitting under mains pressure for weeks is the usual reason a head starts to weep.
What else it gets used for
Cloth nappies, mostly. A directed cold jet over the pan deals with a nappy far better than any amount of rinsing in a sink.
After that: dogs' paws, muddy boots, and the toilet pan itself, which is genuinely quicker to clean with a jet than a brush.
Who finds it useful
Anyone who finds reaching and twisting awkward, which includes people recovering from surgery, later pregnancy, and older users. The handset does the reaching instead of you.
That is a point about how the fitting handles. It is a washing fitting and it treats nothing, and anyone dealing with a medical problem should be talking to a clinician rather than reading a product page.
Hard water
If you are in a hard water area the spray holes will scale eventually, like every other outlet in the house. Wiping the nozzle dry after use prevents most of it, and a wipe with a descaler on a cloth once a month clears the rest. Do not soak the hose fitting to do it.