Water heater leaking? Here's what's actually wrong (and what it costs to fix)

A leaking water heater is the kind of problem that goes from mild annoyance to full bathroom flood very quickly. The good news is that where the water is coming from tells you almost exactly what's gone wrong — and whether you're looking at a 30-minute leak repair or a unit on its way out.

Here are five common leak points. The price figures are SparkFlow guide ranges reviewed on 31 July 2026; access, model and diagnosis can change the quote.

1. Drip from the bottom of a storage tank

This is the worst-case scenario when a technician confirms the tank shell itself is perforated. Water appearing underneath can also travel from a valve or pipe connection above, so the source must be traced before condemning the tank.

• What it means: A confirmed perforated tank is not a durable repair; the unit needs replacement.
• What to do: Turn off the power and water supply immediately. Plan a replacement within days, not weeks — internal pinhole leaks get worse fast.
• Cost: A new 25L storage tank with install runs $280–$650 depending on brand.

Why it happened

Tank material, protective lining or anode, installation, usage, water conditions and model-specific maintenance all affect corrosion. There is no sound rule that an unserviced tank fails in five or six years. Check the manual and warranty, and follow the manufacturer's stated inspection or maintenance schedule.

2. Drip from the pressure relief valve (PRV)

Most storage tanks have a small valve on the side or bottom — the PRV. It's a safety device. When the water inside gets too hot or the pressure too high, it releases a small amount of water.

• What it means: A small discharge during heating may be normal expansion. A continuous drip can indicate a valve fault, debris, incorrect calibration or excessive supply pressure.
• What to do: Do not block or cap the discharge. Have the valve and incoming pressure checked.
• Cost: $80–$120 for a PRV replacement.

Ariston Singapore's storage-heater troubleshooting guidance lists a defective valve or excessive pressure as causes of frequent safety-valve leakage. A thermostat fault is more plausible when water is overheating or scalding, and is a separate diagnosis. If the heater instead has no hot water, the electrical and heating components need their own checks.

3. Drip from the pipe joints (inlet or outlet)

Look at the two pipes connecting to the top or sides of the tank — cold water in, hot water out. If the leak is at the joint where pipe meets tank, this is the most common and easiest fix.

• What it means: The rubber washer or thread sealant has degraded. Usually after 5+ years.
• What to do: Replace the gasket or re-do the thread sealing. 20-minute job.
• Cost: $40–$80 for a callout + parts.

4. Water dripping from an instant heater

Instant heaters can leak in three places, each with a different meaning — and if yours is failing, it's worth weighing whether an instant or storage unit suits your bathroom before you replace it:

From the bottom of the heater unit itself

Likely a cracked heating chamber. These are sealed units — usually not worth repairing. Replace.

From the showerhead connection

A flexible-hose washer or the hose itself may have degraded. Switch off the heater and water supply first, then follow the manufacturer's instructions for approved replacement parts; do not disturb the heater body or electrical connections.

From the wall-mount bracket

Internal joint leak. Same diagnosis as the bottom drip — usually time for a new unit.

5. Water pooling around the base but no obvious source

Sometimes water collects under the unit but you can't spot where it's coming from. Do not assume it is harmless condensation: water can track along pipework or the casing from a fitting above.

Isolate power, avoid touching a wet appliance, contain water without covering vents or electrical parts, and have the pipe joints, valve, hose and casing inspected. A drip tray is not a repair for an unknown leak around a mains-powered appliance.

Should you repair or replace?

Base the decision on the diagnosed source:

A valve, hose or external fitting may be repairable at any age. A confirmed perforated tank or cracked sealed heating chamber generally requires replacement. For other faults, compare parts availability, warranty, repair scope and the price of a compliant replacement.

Age is context, not a diagnosis. Ask what failed, whether the repair is covered, which parts are being replaced and what warranty applies to the work.

Here's how the five leak points compare, so you can see whether you're looking at a small repair or a full water heater replacement:

What to do right now if it's leaking

1. Switch off the power at the dedicated breaker in your DB box, but only if you can reach it from a dry, safe position.
2. Turn off the heater's water inlet only if the valve is clearly identified and safely reachable. Otherwise use the flat's main water valve.
3. Keep clear of the wet appliance. Do not open covers, cap a relief outlet or try to drain a hot tank unless its manual and a qualified technician direct you.
4. Photograph the leak from a safe distance and WhatsApp us. A photo can help narrow the source and guide the quote, but on-site diagnosis confirms it.

Singapore's Consumer Product Safety Office says water heaters should carry a SAFETY Mark, be directly wired through a double-pole switch and be wired by a Licensed Electrical Worker. Our water heater team can trace the leak and quote the repair or a compliant replacement.