The showerhead, and the easiest win in the house
Weak or uneven spray, or jets going off at odd angles, is almost always mineral scale in the nozzles rather than a pressure problem. On our water it happens within a year or two.
Unscrew the head, soak it in white vinegar for a few hours — overnight for a bad one — then scrub the face with an old toothbrush and rinse. Many heads have rubber nozzle tips designed to be rubbed clean with a thumb, which is worth doing monthly in the shower.
If you cannot remove it, tie a bag of vinegar around it so the face is submerged. Less effective, but better than nothing.
Do this before concluding you have a water pressure problem. A scaled head produces exactly the same complaint as low pressure and costs nothing to rule out.
One caution: check the manufacturer's guidance before soaking anything with a specialist finish. Some coatings do not like acid.
Worth knowing
If cleaning the head does not restore the flow, check whether the weakness affects the whole house or just this fixture. Whole-house is a supply issue — see low water pressure. One fixture is the fixture.
The valve cartridge
Behind the handle is a cartridge that mixes hot and cold and shuts the water off. It relies on smooth faces meeting precisely, and scale on either one is all a drip needs.
Symptoms in order of appearance: the handle gets stiff, then the temperature starts wandering during a shower, then it drips when off, then it becomes hard to shut off fully.
Stiffness is the early warning worth acting on, because stiff handles get forced and forcing damages the mechanism — turning a cartridge replacement into a valve body replacement, which means opening the wall.
Cartridge replacement is a contained job when the valve body is sound. Take the old one to the counter rather than describing it; they vary enormously between manufacturers.
If your shower has a pressure-balancing or thermostatic valve, that scale is also degrading the scald protection — the mechanism that stops the shower going hot when a toilet flushes. That is a safety feature, not a comfort one.
Grout, sealant, and the only failure that matters structurally
This is the part people treat as cosmetic and it is the one that damages the house.
Grout is porous. It absorbs water, and once the waterproofing behind the tile is compromised, water reaches the substrate. That is how a shower quietly destroys a subfloor or a ceiling below over months.
Silicone sealant at the corners and along the base is the sacrificial part — it is meant to be replaced periodically, not to last forever. Where it has gone black, is peeling, or has parted from the tile, cut it out and redo it. Corners specifically need flexible sealant rather than grout, because they move.
Cracked or missing grout should be raked out and replaced rather than smeared over.
Loose or hollow-sounding tile is the serious sign. Tap around the enclosure; a hollow note means the tile has debonded from the substrate, which usually means water has already been getting behind it. That is not a maintenance item.
Persistent musty smell, or discolouration on the wall or ceiling on the other side of the shower, means the same thing from the other direction.
The drain
Shower drains block for one reason: hair bound together with soap scum. Individually neither would be much of a problem.
Soap scum is specifically a hard water phenomenon — it is what soap becomes when it meets calcium and magnesium. It is sticky, it grips the pipe wall, and it gives hair something to hold onto. Softer-water regions genuinely have fewer of these calls.
A hair catcher over the outlet prevents most of it and costs almost nothing. Emptying it is unpleasant for four seconds and cheaper than a service call.
Skip the chemical drain cleaner. It damages older pipe and seals, and it will not touch the mat of hair it is being asked to clear.
If the shower gurgles when a toilet flushes, that is not a shower problem — that is a main line symptom, and the shower is just where you can hear it.
What a softener changes
Worth stating plainly, because most of this page traces back to one cause.
Softened water means less scale in the showerhead and on the cartridge faces, so both last longer. It also means far less soap scum, which means fewer drain blockages and dramatically less cleaning — the film on the glass is calcium, not dirt.
It does not eliminate maintenance. Sealant still ages, cartridges still wear, hair still goes down the drain.
But nearly everything on this page is accelerated by 15 to 30 grains per gallon, and treating the water addresses the cause rather than the symptoms one fixture at a time.