First: make it safe
A leaking water heater combines water, electricity and sometimes gas, so safety comes first.
- Turn off the power or fuel. For an electric unit, switch off its breaker. For a gas unit, turn the gas control to the off or pilot setting per the label, or close the gas shutoff. If you smell gas, do not touch switches, leave the building and call your gas utility and emergency services from outside.
- Close the cold water supply valve on the pipe feeding the tank, usually at the top. This stops more water entering.
- Avoid standing in water near electrical equipment. If the breaker panel is in a flooded area, call an electrician.
- Be careful with hot water. Water from the tank or relief valve can scald.
- Contain and dry the area with towels, a pan or a wet/dry vacuum.
Find where the water is really coming from
Water pooling at the base does not necessarily mean the bottom of the tank is leaking. Dry everything with a towel, then check these in order:
- Pipes and connections at the top (cold inlet, hot outlet): water can run down the tank.
- Temperature and pressure (T&P) relief valve and its discharge pipe: if the valve is dripping, water can run down and collect at the base.
- Drain valve near the bottom: look for drips from the spout or handle.
- Gas unit burner area or electric unit element access panels: moisture here can mean a heating element gasket or other issue. Do not open panels on a powered unit.
- Condensation: a cold tank in humid air, or a high-efficiency gas unit, can create moisture.
- Nearby sources: a leaking pipe (see signs of a leaking pipe), washing machine hose or an air conditioner drain (see reasons your AC is leaking water) can pool near the heater.
Common causes
Loose or leaking drain valve
The drain valve can drip from a worn washer or loose connection. Sometimes snugging it slightly helps, but do not over-tighten plastic valves. A faulty valve can usually be replaced.
T&P relief valve discharge
This valve opens when temperature or pressure gets too high. Occasional dripping may be due to high water pressure or thermal expansion, or a worn valve. Never cap or plug the valve or its discharge pipe, because it is a safety device. The discharge can be scalding hot, and the discharge pipe must run downward to a safe drain location so nobody is scalded. A leaking T&P valve should be replaced by a plumber, who can also check pressure and the expansion tank.
Loose fittings or failed connectors
Inlet and outlet connections can leak at threads or flexible connectors. These are often repairable.
Condensation
Moisture beads on the tank or pipes, and puddles can form, but there is no actual leak. It tends to appear in humid conditions or when filling with cold water.
Tank corrosion and sediment
Over years, sediment buildup and corrosion can create small holes in the steel tank. Rusty hot water is an early hint; see light brown water from the faucet. A leak from the tank itself generally cannot be repaired reliably, and replacement is usually needed. Tanks nearing the end of their service life are more prone to this.
High water pressure
Excess household water pressure can stress the tank and valves. A plumber can test pressure and install a regulator or expansion tank if needed; how to fix low water pressure explains how to read a pressure gauge and what a regulator does.
Heating element or gasket (electric)
A leaking element gasket at the side can drip down to the base. Replacement should be done with the power off and the tank drained, ideally by a qualified person.
Can the leak be fixed?
- Fixable: drain valve, fittings, connectors, element gasket. A T&P valve should be replaced by a plumber.
- Usually not fixable: a leak from the tank body. Epoxy and repair kits are sometimes promoted as temporary measures, but they are not a reliable or safe long-term solution for a pressurized tank.
If you cannot find any external source, and water seems to come from beneath the jacket or insulation, the tank has probably failed. Plan for a replacement.
Can I still shower?
Once you have turned the heater off and closed its cold inlet valve, you will not have hot water from it. The rest of the home’s cold water should still work, since the heater’s valve isolates only the tank. Do not run a leaking heater with the power or gas on just to keep hot water available, especially if water is reaching electrical parts or burner components. For a heavy leak, shut off the main water supply and call a plumber.
Cost
Costs vary by region, tank size, fuel type and installation. A drain valve or fitting repair is usually far less than replacing a tank, and replacement costs can be affected by code upgrades, venting and removal of the old unit. Get written quotes from licensed plumbers and ask what is included. If your tank is older, ask about expected remaining life before investing in repairs.
When to call a professional
- water comes from the tank body or you cannot find the source
- the T&P valve discharges repeatedly or hot water flows from it
- you have a gas unit and any gas smell, soot or CO concern (leave and call emergency services)
- there is flooding near electrical equipment
- you need to replace the heater, which often requires permits, venting and gas or electrical work
Prevention
- Flush the tank periodically per the manufacturer’s instructions to reduce sediment.
- Check the anode rod on the schedule the manual suggests, and replace it when worn.
- Test the T&P valve according to the manufacturer’s directions, keeping clear of the discharge, which can be scalding hot. Have a plumber replace the valve if it leaks or does not flow.
- Consider a drain pan with a drain line, especially if the heater is above finished space.
- Keep an eye on water pressure.
FAQ
What should I do if my water heater is leaking from the bottom? Turn off power or gas, shut off the cold water supply, contain the water and find the source. Call a plumber if it is the tank.
Is the leak a sign it needs replacing? If the tank body is leaking, usually yes.
Is this similar to a boiler leak? Boilers hold hot water in a closed heating loop. See is a boiler leaking water dangerous.
Could the water be from my furnace instead? If the heater is nearby, yes. See why a furnace leaks water in summer and is water leaking from a furnace dangerous.