No hot water in Johannesburg? 7 geyser problems and how to diagnose them
You turn on the shower and the water runs cold. You check the hot tap at the basin cold. You go to the kitchen cold. Something has gone wrong with the geyser, and you need hot water. The question is whether this is a five-minute fix at the distribution board or a job that requires a qualified technician and a replacement part.
In Johannesburg, geyser problems are the single most common residential plumbing complaint — and load shedding has made them more frequent. Power surges when electricity is restored after an outage can trip breakers, damage thermostats and cause pressure relief valves to open unexpectedly. Most homeowners who wake up to no hot water have one of seven problems. This guide walks through each one: what causes it, how to check for it yourself, and what it means for the repair.
Before you start: two safety checks
Before touching any geyser components, confirm two things.
First, make sure the geyser’s isolator switch is on. Your distribution board has a dedicated circuit breaker or isolator switch usually labelled “geyser” or “water heater” that controls power to the unit. If load shedding has recently ended or there has been a storm overnight, this breaker may have tripped to the off position. Check that it is switched fully on before concluding anything else is wrong.
Second, check whether the cold water supply to the geyser is open. There is a dedicated isolation valve on the cold water inlet pipe feeding the geyser typically a lever handle or a round knob near the unit. If this valve was partially or fully closed during maintenance or after a leak, the tank will not refill correctly and hot water will run out quickly.
Neither of these checks requires any tools. If both are confirmed and the problem persists, work through the diagnostics below.
Problem 1: Failed geyser element
What it is: The geyser element is an immersion heater, a resistive coil submerged inside the tank that heats the water. Over time, elements corrode, scale up with limescale from Joburg’s mineral heavy water supply, or fail from the electrical stress of repeated power surges.
Symptoms: No hot water at all despite the geyser having power. The unit is silent, no heating sound, no thermostat clicking. The cold water supply is confirmed open. Water in the tank is cold even several hours after power has been restored.
How to check: Touch the pipe on the outlet side of the geyser (the pipe carrying hot water to your taps) after the geyser has had at least an hour of uninterrupted power. If the pipe is completely cold, the element is almost certainly not heating. A visual check of the element itself requires draining the tank this is the point where the diagnosis crosses into repair territory.
What it means: Element replacement is a same-day repair in most cases. The old element is drained and removed, a new element is installed, the tank is refilled and tested. It is straightforward work but must be done by a registered professional under SANS 10254 — any geyser repair that involves opening the vessel requires a Certificate of Compliance on completion.
Problem 2: Faulty or tripped thermostat
What it is: The thermostat regulates water temperature inside the tank, switching the element off when the set temperature is reached and back on as the water cools. Most Johannesburg geysers are set between 55°C and 65°C. A thermostat that has failed open leaves the element permanently off; one that has failed closed leaves it permanently on eventually triggering the safety cutout or the pressure relief valve.
Symptoms: Water runs cold despite the geyser having power and the element being intact. Alternatively, water scalds at the tap well above the expected temperature, suggesting the thermostat is not cutting off correctly. After load shedding, a thermostat’s thermal cutout a small red reset button, usually accessible behind a panel on the side of the unit sometimes trips as a safety response to the power restoration surge.
How to check: Locate the thermostat housing on the side or base of your geyser. Behind a small removable panel, there is usually a red or black reset button. Press it firmly and wait 60 to 90 minutes for the water to reheat. If the problem does not recur, the cut out tripped during an outage and has now been reset. If hot water fails again within a day or two, the thermostat itself requires replacement.
What it means: Thermostat replacement is a relatively minor repair. It does not require draining the tank and can usually be completed in under an hour. The component is inexpensive; the labour is the primary cost.
Problem 3: Geyser timer set incorrectly
What it is: Many Johannesburg homeowners install a geyser timer — a programmable switch that limits geyser heating to certain hours to reduce electricity consumption. After load shedding disrupts the mains supply, the timer’s internal clock can reset to the wrong time, causing the unit to heat during off-peak hours and be cold during the times you actually need it.
Symptoms: Intermittent hot water present at certain times of day and absent at others with no apparent pattern. Hot water that was available last night but is cold this morning. A display on the timer control showing a time that does not match the current time.
How to check: Locate the timer it is either on the geyser itself, in a separate control box near the unit, or on the distribution board. Check whether the programmed “on” periods correspond to the correct current time. After load shedding, the clock often defaults to 12:00 or 00:00 and needs to be manually reset.
What it means: Reset the timer clock and confirm the heating windows cover the hours when you need hot water. If the timer display is blank or the unit will not accept programming, the timer itself has failed and requires replacement.
Problem 4: Air lock in the hot water pipes
What it is: An air lock occurs when a pocket of trapped air forms in the hot water supply pipework, blocking water flow to one or more outlets. This can follow a mains supply interruption — such as a City of Johannesburg maintenance shutdown — when air enters the empty pipes as water pressure drops and is not fully purged when supply is restored.
Symptoms: Hot water works at some taps but not others. A tap delivers only a trickle, or spits intermittently, or produces water with unusual pressure fluctuations. The problem appears suddenly after a water supply outage in your suburb.
How to check: Open the affected hot tap fully and let it run for 30 seconds. If the flow begins intermittently, spits and then gradually stabilises, an air lock is working itself out. Turn all hot taps in the house on simultaneously to help purge the remaining air from the system. The problem often resolves itself within a few minutes of full flow being restored.
What it means: Air locks following supply interruptions usually clear without intervention. If the problem persists after purging all taps, there may be a fault in a check valve or a section of the pipework that is trapping air consistently which warrants a proper inspection.
Problem 5: Pressure relief valve discharging or failing
What it is: Every geyser is fitted with a pressure relief valve (PRV) a safety device that opens automatically to release water if pressure or temperature inside the tank exceeds safe operating limits. A dripping or continuously discharging PRV means the valve is either doing its job in response to a genuine overpressure condition, or the valve seal has deteriorated and it is leaking when it should be closed.
Symptoms: A slow but constant drip from the small discharge pipe running from the side of the geyser to the drip tray or down the outside wall. Water staining on the wall below the discharge point. The sound of water dripping into the drip tray even when no taps are running.
How to check: A small occasional drip during and immediately after the geyser heats is normal thermal expansion causes a modest pressure rise that the PRV is designed to vent. A continuous drip, a steady stream or a discharge that does not stop after the heating cycle ends indicates either excessive system pressure or a failing valve.
What it means: This is the point to call a qualified plumber. A discharging PRV is not a problem to ignore or to temporarily silence by plugging the discharge pipe that creates a dangerous overpressure condition. The professional will test system pressure, check whether the expansion vessel (if fitted) is functioning correctly, and either replace the PRV or address the underlying pressure issue. Left unattended, a continuously discharging PRV can drain significant quantities of hot water daily adding substantially to both your water and electricity bill.
Problem 6: Burst or leaking geyser vessel
What it is: A geyser vessel the steel tank that holds the water has a typical lifespan of 8 to 12 years under normal Johannesburg water pressure and mineral conditions. The anode rod inside the tank sacrificially corrodes to protect the vessel walls, but once the anode rod is depleted, the tank itself begins to corrode. Eventually, the internal lining fails and the vessel begins to leak from a seam, a fitting point or through corrosion-thinned steel.
Symptoms: Water appearing around the base of the geyser or saturating the drip tray continuously. A damp or wet ceiling below the geyser cupboard. Water staining on ceiling boards directly beneath the unit. A significant drop in hot water volume — the tank is not holding its full capacity because it is leaking from inside the insulating jacket.
How to check: Inspect the drip tray beneath the geyser. A dry drip tray that suddenly contains standing water — not from the PRV discharge point but collecting from above or the sides of the tank — indicates the vessel is leaking externally. Isolate the cold supply to the geyser and switch off power at the distribution board while you confirm the source.
What it means: A burst or leaking geyser vessel requires full replacement — there is no repair for a failed tank. A geyser technician will assess the correct replacement size for your household’s demand, advise on upgrading to a heat pump or solar geyser where energy efficiency is a priority, and complete the installation in compliance with SANS 10254. The Certificate of Compliance issued on completion is your legal record of the installation and the document your insurer requires.
Problem 7: Heat pump or solar geyser fault
What it is: Heat pumps and solar geyser systems are more complex than conventional resistance element geysers. Heat pumps use a refrigerant cycle to extract heat from the ambient air; solar systems use roof-mounted collectors connected to either a direct or indirect circulation system. Both have additional components that can fail independently of the tank itself.
Symptoms for heat pumps: The unit is running, you can hear the compressor and fan but water is not heating. Alternatively, the heat pump has shut down completely and defaulted to backup element heating. Error codes displayed on the heat pump control panel. Unusual noise from the outdoor unit — grinding, hissing or clicking that was not previously present.
Symptoms for solar geysers: Hot water production is significantly reduced on sunny days when it should be at its best. The collector panels are visibly undamaged but output is low, suggesting a circulation pump failure, a blocked collector circuit or a failed differential controller that is not activating the pump at the correct temperature differential.
What it means: Heat pump and solar geyser diagnostics require a qualified technician with specific system knowledge — the fault could be electrical, refrigerant-related, hydraulic or in the control system. Attempting DIY repairs on a heat pump refrigerant circuit voids the manufacturer’s warranty and, in most cases, makes the fault worse. Energy efficiency certificates and manufacturer warranties on heat pump systems also require that all service work is carried out by a registered professional.
When to call and what to tell the technician
If your checks have identified or ruled out the problems above, here is what to tell a plumber when you call to ensure the visit is efficient and the repair is completed in a single trip:
- The geyser brand and model (usually on a label on the side of the tank or the drip tray)
- Approximate age of the unit, if known
- Whether the problem appeared suddenly or has been developing gradually
- Whether load shedding occurred in the 24 hours before the fault appeared
- Whether the PRV or drip tray shows any signs of discharge
- Whether the problem is total loss of hot water or reduced temperature/volume
This information allows the technician to arrive with the most likely replacement components on the vehicle and complete the diagnostic more quickly once on site.
Hero Plumbers geyser repairs and replacements across Johannesburg
Hero Plumbers handles geyser element replacements, thermostat faults, PRV replacements, full vessel replacements and heat pump service calls across the full Johannesburg metro. All geyser work complies with SANS 10254.
Same day appointments are available across most Johannesburg suburbs. For urgent geyser failures, our emergency line operates around the clock.
Contact Hero Plumbers
Phone: +27 70 322 0416
Email: [email protected]
Frequently Asked Questions
1. Why do I have no hot water after load shedding?
Power surges when electricity is restored can trip breakers, damage thermostats, or trip the thermal cutout check the isolator switch at your distribution board and the thermostat’s red reset button first.
2. How do I know if my geyser element or thermostat has failed?
If the pipe leaving the geyser is completely cold after an hour of power, the element likely isn’t heating. If water is cold but the element seems fine, or water is scalding, suspect the thermostat.
3. Is it normal for my geyser's pressure relief valve to drip?
A small drip during/after heating is normal (thermal expansion). A continuous drip or steady stream is not that needs a plumber.
4. How long does a geyser last in Johannesburg?
Typically 8 to 12 years, depending on water pressure and mineral content, before the anode rod depletes and the tank itself starts corroding.
5 Why does my hot water work at some taps but not others?
Likely an air lock often after a mains supply interruption. Try running all hot taps simultaneously to purge trapped air.
6. Why is my geyser timer heating water at the wrong times?
Load shedding can reset the timer’s internal clock (often defaulting to 12:00 or 00:00), so it heats during off-peak hours instead of when you need it.
7. Can I fix a leaking geyser myself?
No. A leaking/burst vessel requires full replacement, not repair, and must be done by a PIRB-registered professional under SANS 10254 with a Certificate of Compliance.
8. My heat pump/solar geyser isn't heating properly can I fix it myself?
No. DIY repair on refrigerant circuits voids warranties and can worsen the fault; this needs a technician with heat pump/solar-specific expertise.
9. What information should I have ready before calling a plumber?
Geyser brand/model, approximate age, whether the fault was sudden or gradual, recent load shedding, any PRV/drip tray discharge, and whether it’s total loss or reduced hot water.
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