Why does my water heater leak occasionally?

An occasional leak from your water heater is a serious warning sign that should never be ignored — even a small drip can indicate a failing component, and in the worst case, it can lead to flooding, mold, or a complete tank failure.

The most common culprit is the temperature and pressure relief (T&P) valve. This safety valve is designed to release water when pressure or temperature inside the tank gets too high. If you notice water dripping from the small pipe connected to this valve (usually on the side or top of the tank), it could mean the valve is doing its job temporarily — or it could mean the valve itself is worn and needs replacement. A faulty T&P valve is not something to ignore; it's a critical safety device.

Another frequent cause is a corroded or loose drain valve at the base of the tank. Over time, this valve can develop a slow drip, especially in older units. Similarly, loose inlet and outlet pipe connections at the top of the tank can weep water, particularly if the fittings have experienced thermal expansion and contraction over many heating cycles — which is very common in Toronto homes that see significant temperature swings between seasons.

If the leak appears to be coming from the bottom of the tank itself, that's the most concerning scenario. It typically means the tank's inner lining has corroded and is failing. Unfortunately, there's no repair for a leaking tank — replacement is the only option.

Toronto-Specific Context

Water heaters in the GTA typically last 8–12 years. If your unit is approaching or past that age, a leak is often the beginning of the end. Toronto's water supply, while treated, does contribute to mineral buildup and anode rod depletion over time, which accelerates internal corrosion. Replacement costs in Toronto typically run $1,200–$2,500 installed for a standard 40–60 gallon natural gas unit, depending on the brand and any venting modifications needed. Heat pump water heaters run $2,500–$4,500 but offer significant energy savings.

Gas water heater work in Ontario must be performed by a TSSA-licensed technician — this is not a DIY project. Even replacing a T&P valve on a gas unit should be handled by a licensed professional to ensure proper testing and compliance.

What you should do right now: Place a dry towel or paper towel near the leak and check it in a few hours to gauge how much water is accumulating. Take a photo of where exactly the leak is coming from. Then contact a licensed plumber or HVAC technician to inspect the unit — ideally within the next day or two. If the leak is significant or worsening, don't wait.

You can find licensed, vetted water heater professionals in your area through the Toronto Construction Network directory. Don't let a small drip turn into a flooded basement.