3. A shower that has lost its pressure
When a shower gradually weakens over months, the cause is nearly always blocked nozzles rather than a supply problem. Scale forms inside the head where water sits hot and still between uses.
Test it first: run the shower and look at the spray pattern. Jets going sideways, missing entirely, or a noticeably narrower cone mean scale, not pressure. If every nozzle flows weakly and evenly, the issue is elsewhere in the plumbing.
For a detachable head, unscrew it, take out the rubber washer and filter screen if present, and submerge the whole head in a bowl of warm citric acid solution for an hour. Then push each nozzle with a thumb — most modern heads have rubber nubs specifically so deposits can be rolled out — or clear them with a pin. Rinse and refit.
For a fixed head, fill a strong food bag with the solution, raise it so the head is submerged, and secure it with a rubber band or cable tie for an hour. Empty, run the shower hot for a minute to flush debris.
Do the same for the tap aerators on the basin and bath while you have the solution mixed. Unscrew the nozzle with a cloth to protect the finish, soak the parts, brush and refit.
Repeat quarterly in a hard-water area. Also check the filter screen at the hose connection of an electric shower, which clogs with grit and is the most commonly missed cause of a weak flow.