Water Heater Repair
Work out why showers run lukewarm, why a tank drips, popping sounds and dead pilots or elements. Open page
Plain-English article
Water Heater Leaking From the Bottom in Thornton, CO
Water on the floor around a water heater is a sign to act, not to wait. Some leaks come from a fitting that can be fixed, and others mean the tank has failed.
By the Thornton Plumbing Co. team ·
Shut things down first
Turn off the power or the gas to the heater. For an electric unit, switch off the breaker. On a gas unit, set the gas control to off. Then Shut the cold water valve above the heater.
If the leak is heavy, crack open a hot tap elsewhere in the house so the tank can vent, and run a hose from the drain valve to a floor drain or outdoors. Mop up and place a pan or towels.
Where the water is coming from
Check the pipe connections on top, the pressure relief valve and its discharge pipe, the drain valve low on the tank and the tank seam. Water on top may run down and look like a bottom leak.
If the water comes from a fitting, tightening or replacing it may fix the problem. If it comes from the tank wall or the bottom, the tank has rusted through.
Common causes
A loose or corroded drain valve is a frequent cause. A pressure relief valve that drips can mean pressure is too high or the valve has worn. Condensation on a gas unit can mimic a leak, especially in cold weather.
A tank leaking along its bottom has typically failed from corrosion. Hard water scale hastens the damage. The anode rod protects the tank, but it wears out and needs checking.
Where the water comes from
Where the leak sits tells you whether to repair or replace.
| Source | Repair or replace | Notes |
|---|---|---|
| Drain valve | Repair | A new valve is a short job |
| Pipe fitting on top | Repair | Tighten or replace the fitting |
| Pressure relief valve | Repair | Check pressure and expansion |
| Tank wall or bottom seam | Replace | The tank has rusted through |
Repair or replace
A fitting or valve can be repaired in a short visit. A failed tank must be replaced. Age is a clue: many tanks last about ten years, and some less in hard water.
If your tank is old, replacement is the safer choice. Compare the options on the replacement page and the tankless page.
Protect the floor
A drain pan under the heater with a pipe to a drain limits damage. In a finished basement, a leak sensor with an alarm can alert you early. Check the pan occasionally.
If water has reached carpet or drywall, dry it quickly. See water damage restoration for what a drying plan involves.
Maintenance
Flush the tank each year to remove sediment. Test the pressure relief valve by lifting the lever briefly. Check the anode rod every few years.
Hard water is a fact of life in Thornton. The city's 2025 report lists an average near 13.5 grains per gallon, so scale builds faster than in a soft-water area. A softener helps, and see water heater repair for service.
Where the water is really coming from
Water pooled under a heater is not always a sign that the tank has failed. Check the supply and outlet connections at the top, the T&P relief valve and its discharge pipe, the drain valve at the bottom, and any pipe fittings. A dripping fitting can run down the side and gather at the base.
Dry everything with a towel, then watch each spot. Water that returns from a seam in the tank itself, or from the bottom edge where the shell meets the base, is the pattern that signals a failed tank.
Why a tank fails
Within a steel tank, a glass lining and an anode rod resist corrosion. As the rod is used up and sediment builds, the steel is exposed. In water as hard as Thornton's, scale can speed that along, and sediment makes a burner overheat the bottom of the tank. Eventually a pinhole opens and the water leaks.
A tank in that state cannot be repaired. Replace it. A leaking relief valve or a loose drain valve can be fixed, though, so check before you assume the worst. See water heater repair and water heater installation and replacement.
What to do right now
Kill the power first. Flip the breaker for an electric heater, or set the gas control to off. Shut the cold supply valve above the tank. For a heavy leak, shut off the main water valve. Open a hot tap upstairs so the tank does not form a vacuum as it drains.
Move items off the floor, and mop up so the area does not stay wet. A heater in a finished basement can soak carpet and drywall quickly. If water spreads, see water damage restoration.
Planning the replacement
Decide between a standard tank and a tankless unit, and check the venting, gas line size and electrical supply before you pick a model. Ask whether the contractor will haul the old unit and handle the permit, and about a drain pan with a drain line, which keeps the next leak off the floor.
Ask for the model's warranty terms in writing, and what the installer's own warranty covers.
Safety around the unit
Do not touch a heater that is surrounded by water until the power is off, and do not reach into water near an electrical panel. If the heater is gas fired and you smell gas, leave first. A relief valve that discharges hot water can scald, so keep children and pets back from the discharge pipe. If you are unsure about any of this, call.
Quick answers
Asked about leaking water heater
It can damage floors and walls, and electric or gas units pose other risks. Shut off power or gas and water, then call.
Not usually. If the tank itself leaks, it must be replaced.
Possible causes are high pressure, thermal expansion or a worn valve. A plumber can check.
Many last about ten years, depending on water quality and care.
Connected services
Water Heater Installation & Replacement
Remove a dead tank and install a unit sized, fueled and vented to suit how your household uses hot water. Open page
Tankless Water Heater Service
Flush scale from an on-demand heater, repair it or replace it, with the setup this elevation calls for. Open page
Related reading
Locating your main water shutoff
Know where it is before the flood. Here is how to find your main shutoff, test it and what to do if it will not turn. Open page
Hard water in Thornton
Thornton's water is hard. Here is what the city's own report says, what scale does to heaters and fixtures and what helps. Open page
Water hammer: the banging pipes
A bang in the wall when a tap or washer shuts off is water hammer. Here is what causes it and which fixes work. Open page
Water around the heater?
Shut off power and water, then call the 24/7 line.