Quick answer
Slow heating points to a partly failed element, heavy scaling, a geyser undersized for the household, or a thermostat cycling early. A 150L geyser should reach temperature in roughly one and a half to two and a half hours from cold. If yours has drifted past three hours and used to be quicker, you have lost element output — usually to scale, sometimes because one element of a dual-element cylinder has failed.
Common causes
- Scaled element transferring heat poorly into the water
- Geyser undersized against actual hot-water demand
- Element failing and working at reduced effective wattage
- One element of a dual-element geyser burnt out
- Cold winter inlet water extending heat-up time — a genuine seasonal effect, not a fault
- Thermostat cutting out early through drift or a poor sensor contact against the cylinder
What you can do now
- 1Time a full reheat from cold — 150L should take about 1.5 to 2.5 hours
- 2Compare against last summer; a seasonal slowdown is normal, a year-on-year slowdown is not
- 3Check the thermostat setting is 60–65°C and has not been knocked down
- 4Listen for popping during heating, which confirms scale on the element
- 5Count the household's peak simultaneous hot-water draws to sanity-check the cylinder size
When to call a professional
If reheats consistently exceed three hours, book a service and an element check. A descale and element replacement restores the original heat-up time and costs far less than the extra electricity a scaled element burns over a year. If the geyser is correctly sized and freshly serviced but still slow, ask for the element wattage and the thermostat calibration to be verified.
Typical cost in Johannesburg
Service + element R1,500–R2,400
Indicative ranges only. We provide written, itemised quotes before any work.
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