Over the years, the inner tank rusts and corrodes from constant heat and water pressure. Once the liner cracks, water seeps out from the bottom — and because that water sits against the live heating element, the leak is now an electrical problem too, not just a plumbing one.
Yes — genuinely. Water mixing with electricity inside the tank can electrify the whole casing, and even the hot-water tap downstream. The result can be a fatal shock or a major trip in your DB box. Isolate the power at the wall switch and MCB before you touch anything.
If the inner tank is cracked, it cannot be welded or patched — the unit must be replaced. Have a licensed plumber fit the new heater so the temperature-and-pressure relief valve is installed correctly; a wrongly fitted valve on a storage tank is a real safety hazard. Not sure if it is the tank or just a leaking fitting? A plumber can usually tell within minutes on site.
What to do right now (before you call anyone)
If you can see water dripping or pooling under a storage water heater in your HDB flat, condo or landed home, treat it as a live electrical hazard, not just a plumbing leak. Water inside a cracked tank sits directly against the heating element, so the metal casing — and even the hot-water tap downstream — can become electrified. Work through these steps in order:
- Switch off the heater at the wall isolator first (the dedicated double-pole switch beside the unit), then trip its dedicated MCB in the DB box. Never touch the heater casing while it is still powered.
- Close the heater's inlet stop valve — the small lever or wheel on the cold-water pipe feeding the unit. This stops fresh water refilling the cracked tank.
- Keep hands and feet dry. Do not stand in the puddle while flipping switches. If the floor is wet, switch off power at the main DB first.
- Stop using that bathroom's hot water until a licensed plumber has confirmed the unit is isolated and safe.
In Singapore most storage heaters are mounted high on the bathroom wall, inside the HDB bomb shelter (household shelter), or in the service yard. A leak from a ceiling-mounted unit can also drip into your neighbour's unit below in a condo, so isolating the water early limits damage and disputes.
Storage vs instant: which heater do you actually have?
Knowing your type changes the fix and the cost. A storage heater has a bulky insulated tank (25–91 litres) and is the type that rusts and cracks from the inside. An instant heater is a slim wall box with no tank — it rarely "leaks from the bottom" the way a corroded tank does; a dripping instant unit is usually a loose fitting or a failed gasket, which is repairable. If your leak is from a tanked unit and the water is rusty or warm, the inner tank is gone and replacement is the only safe option — a cracked liner cannot be welded or patched.
When to DIY vs call a pro
DIY ends at isolation. Switching off power, closing the stop valve and mopping up are fine for any homeowner. Everything past that — removing the old tank, fitting a new temperature-and-pressure relief valve, re-sealing connections, and re-energising the circuit — should be done by a licensed plumber, and any wiring change by an EMA-licensed electrician. A wrongly fitted pressure relief valve on a storage tank is a genuine safety risk, and DIY water damage is rarely covered by HDB or condo insurance.
Indicative replacement & repair costs in Singapore
Prices below are indicative only and confirmed on site after the technician sees the model, mounting height and pipe condition.
| Job |
Typical indicative cost |
Notes |
| Plumber callout / inspection | from S$60–S$80 | Often waived if you proceed with works |
| Remove & dispose old storage tank | from S$80 | Higher if ceiling/shelter mounted |
| Supply & install new storage heater | typically S$220–S$450 | Varies by litre capacity & brand |
| Replace instant heater | typically S$150–S$320 | Labour-only if you supply the unit |
| Re-wire heater circuit / new isolator | from S$80 | EMA-licensed electrician work |
See full ranges on our water heater installation cost and plumber cost pages. If the leak tripped your DB or you smell burning, also check our electrician cost guide — a leak that damaged the wiring needs a licensed electrician, not just a new tank.
Frequently asked questions
My heater leaks only when it's on — is the tank cracked?
Not always. Heat makes metal expand, so a worn gasket or loose union can weep only at full temperature while a cracked tank usually drips constantly and the water is rusty. A plumber can tell the difference in minutes; if it is the inner tank, replacement is the only safe fix.
Can I still shower if I just switch the heater off?
Cold-water use is fine once power is off, but do not use the hot tap from a leaking storage unit — the water sitting in a cracked, still-powered tank is the shock risk. Isolate power at the wall switch and MCB first, then arrange replacement.
How long does a water heater replacement take?
A like-for-like storage or instant heater swap typically takes about 1–2 hours once the technician is on site. Ceiling-mounted or bomb-shelter units, or jobs needing new piping or wiring, take longer and are confirmed after assessment.
How long should a storage heater last in Singapore?
Around 8–12 years with normal use. Singapore's treated water is gentle, but constant heating still corrodes the inner tank over time. If yours is past 10 years and starting to leak, replace rather than repair.
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