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 the 5 most common leak points, in order of how often we see them in Singapore homes.

1. Drip from the bottom of a storage tank

This is the worst-case scenario. If water is coming from the underside of the tank itself (not the pipes connected to it), the inner steel tank has corroded through.

• What it means: The unit is finished. You can't repair a perforated tank.
• 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

Storage tank lifespan in Singapore is usually 8–12 years. Limescale and chloride in the water slowly eat away at the inner lining. If the tank was never part of a regular water heater servicing routine, that timeline shortens to 5–6 years. If you bought a budget brand, even shorter.

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: Either the PRV is doing its job (occasional small release is normal), or it's stuck open and constantly dripping.
• What to do: If it's a slow steady drip, the valve needs replacing.
• Cost: $80–$120 for a PRV replacement.

If your PRV keeps releasing water frequently even when the heater isn't running, the thermostat might be failing and keeping water too hot — the same fault that can leave you with no hot water at all. Get that diagnosed before it does more damage.

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

The flexible hose washer has degraded. $20–$40 fix, often DIY-able if you're comfortable using a wrench.

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. Two likely culprits:

• Condensation: Common with newer instant heaters in humid bathrooms. Not a leak — install a small drip tray if it's bothering you.
• Slow pinhole leak from above: Run a dry tissue along all the pipe joints. The first one to darken is your source.

Should you repair or replace?

A useful rule of thumb in Singapore:

If repair cost is more than 40% of replacement cost, replace. If the unit is over 8 years old, replace.

Why? Because once one part starts failing, the others are usually not far behind. Spending $150 to repair an 8-year-old tank just means you'll spend another $200 fixing the next thing 6 months later, then buy a new tank anyway.

Here's how the five leak points stack up at a glance, so you can see at a glance 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.
2. Turn off the water supply at the inlet valve to the heater (not your main flat valve — there's usually a small one right at the heater).
3. Open the hot water tap somewhere in the house — this releases pressure inside the tank.
4. Photograph the leak — pipe joint, valve, base, etc. — and WhatsApp us. We can usually tell you the likely cause and ballpark cost from a single photo.

Most leaking water heater jobs our water heater team attends in Singapore can be diagnosed in 10 minutes on-site. The hardest part is just knowing when to call vs when to live with it. Hopefully this gives you the framework to decide.