Before you being working on the water heater, turn off the power and gas to the heater to avoid possible shock or burns.
See also: Water heater leaking from the TOP
Leaking from the Bottom of the Tank: Finding the Source
The first places to check if it appears that you have a leak from the bottom of your water heater are the drain valve and temperature & pressure relief valve (T&P valve).
The leak may actually be at the top of the water heater and simply running down through the body of the heater before escaping at a lower level. Look for any visible signs of a leak on the top of the water heater and all pipes leading to or away from the heater. You can also remove the access panels (on electric models) and check for moisture in the insulation.
Common Causes of Water Heater Leaking from the Bottom
Leaking Drain Valve
All water heaters have a drain near the bottom of the unit so that the tank can be emptied before removal, or during routine cleaning of the tank itself. A leaking drain valve can be identified by moisture or water dripping, either out of the drain opening or around the valve itself.
Check to make sure that the bottom valve is fully closed by turning the valve control clockwise. If this does not solve the problem, the valve may need to be replaced.
To replace the valve, you will need to connect an ordinary water hose between the drain outlet and an outside location. Next, turn off the water inlet for the tank, usually located at the top of the water heater on the cold water line. Open the drain valve and allow the tank to empty.
Replacement valves for hot water heaters are available at most hardware stores, and can be replaced with only a wrench. Turn the existing valve counter-clockwise to remove it.
Wrap the threads of the replacement drain valve with plumber’s (Teflon) tape or joint compound, and then screw the new valve into the opening until it is hand tight. Using a wrench, tighten the drain valve 1/2 turn, or until the drain is tightly in place.
Leaking Pressure Relief Valve
The pressure relief valve (T&P valve) is an important safety measure for your water heater to relieve excess pressure if the water heater gets too hot. On most water heaters, the pressure relief valve is on top of the unit, but most systems include a tube attached to the valve in order to channel the water to the floor.
When the T&P valve is leaking, it may appear the issue is at the bottom of the tank since the overflow tube discards the expelled water underneath it. Since the T&P valve is designed to allow water to be released from the tank, the first thing to do is check the thermostat setting to make sure that it is not turned up too high.
If the temperature is fine, you will likely need to replace the pressure relief valve.
Water heaters that are not cleaned out periodically can build up sediment in the tank. Salt and other chemicals in the sediment may lead to premature rusting or corrosion inside of a water heater and eventually cause pinhole leaks to form.
Once a pinhole leak is opened up, the pressure of the water inside the tank forcing its way through the opening will cause the leak to get larger over time.
I’ve heard cases where a leak in an inside closet allowed a stead source of water under the crawl space. Next thing the homeowner knew, they were trying to get rid of a family of chipmunks living under their home.
The best solution for this problem is to replace the tank with a new unit. A leaking tank is an obvious sign of a water heater needing to be replaced.
Normally, replacing a water heater should be done by a professional but if you’re a DIYer, you can do it yourself. On most models, you will need to remove the plumbing connected to the water heater, and disconnect the power inside the access panel. For gas water heaters, be sure to turn off the gas line leading to the water heater, and disconnect the line where it enters the tank.
Replace the water heater with a new unit and reconnect the pipes and power. “How long do water heaters last?” is question usually related to the water heater tank itself. When the tank is damaged, it’s time for a new unit.
Some water heaters may experience condensation on the water tank. This more common on older water heaters, but it can happen to newer tanks if the insulation has been damaged or the thermostat is set too high for safe operation. Allow the tank to sit idle for several hours with the power or gas turned off.
If the leak stops, it is an indication that you are experiencing condensation. Turn down the thermostat and restore power to the unit.
If the problem persists, you may need to replace the tank with a better insulated model. See our list of recommended water heaters to see just how well insulated current models have become.
Condensation may also occur temporarily after a new water heater is installed and the cold water that fills up the tank hasn’t had a chance to heat up yet. The temperature difference between the inside of the tank and the outside air oftentimes causes condensation.