The tank that overflowed at 4am - and the pump that ran itself dry: two faults, one float

On a day when the supply ran late and the pump ran on, most households learn about their water system in one afternoon: the road outside flooded with the tank's entire holding, or the pump's burning smell behind the door. Both events are the same two components - the float valve that stops the fill and the flow that keeps the pump's guts cool - and both have a small repair, a habit, and an explanation worth the whole page.

The overflow: the system's own witness

The overflow pipe is not a fault; it is the float valve's alarm, and the flooded compound is the sound of the alarm being obeyed. The float's job: when the water lifts the ball to its set height, the valve seats and the fill stops - and it fails three ways. The seal at the seat fouled with grit (the borehole's own silt doing what the kettle article describes from the other end - a clean and re-seat fixes it that morning); the float set too high or holed with water inside, so it never lifts (replace, and set the level below the pipe's crown - the gap is the whole design); or the valve's arm bent and jammed, which is the post-storm failure and the reason the lid is inspected after every violent rain. The two-minute test, with the tank nearly empty: lift the float by hand - the valve should shut the flow with no drama and no weep. That single test is the entire overflow article if you only keep one line.

The pump that ran dry

A centrifugal pump moves water and is cooled and sealed by the water it moves; with the suction dry, the mechanical seal runs hot in minutes and the impeller's clearance changes for good - the "it pumps weak now" after a dry-run is the seal's resignation. The fault list, and their fixes, in order of the money they save: the suction strainer blocked (the well's sand, the tank's debris - clean it, and the reason it was blocked); the foot valve stuck with grit so the line drains back between runs (the prime-loss article on this desk covers the same valve from the borehole end); a leak on the suction side letting air in so the pump never fully fills (the hiss at a joint in the primed system is the diagnosis, and a new gasket or union is the whole repair); and the switch - the pressure tank's control or the float's own - that kept the pump calling for water it did not have, which is where the dry-run protection belongs and where most installs skip it: an inexpensive pressure switch with a no-flow cut-out is the device that makes the dry-run a five-second incident instead of a replacement.

The habit list that ends both faults

The lid is on, always (the mosquito article's breeding point and this one's grit point are the same lid); the float lift-test once a month at the low water point; the strainer cleaned each time the borehole runs yellow; the pump's stop-start in a quiet hour listened to like a doctor (the short cycle that repeats is a pressure tank's air charge or the switch itself - both cheap, both urgent before the second season); and the overflow's exit watched, because a trickle on the compound after the tank is full is a float not seating, and a float not seating is ten thousand litres and the neighbour's side of the wall. Water systems keep score in litres; the page's whole argument is reading the scoreboard while the water is still inside.