There are several methods of stopping a leak in a hot water tank, the one used depending on the size of the opening. It should be remembered, however, that a tank that has rusted through in many spots or has opened up at the seams cannot be readily patched by the home mechanic. In most cases, it is cheaper to purchase a new tank than to repair an old one in such poor condition that it will require constant attention.
Large leaks and open seams require welding, or other methods of repair, that the home mechanic does not have the equipment to undertake.
Small, pin point leaks in a tank can often
be stopped by pointing a thin piece of wood, such as a toothpick, and
driving it into the opening. The water inside the tank will cause the
wood to expand, and it will form a tight but not permanent plug.
Drain the water in the tank below the level of the leak. Close the inlet valve so that the tank will not fill up while you are working. If the leak is at the bottom of the tank, turn off the heater. Use a hand drill to drill the hole in which the toggle bolt is inserted.
Make the hole large enough for the toggle bolt to slip through. After the hole has been made, insert the toggle bolt so that the wings attached to the end of the bolt will open on the inside of the tank. Have the washer on the outside of the tank. Tighten the bolt carefully, so that the washer is pulled tight against the side of the tank and covers the hole. Do not try to tighten the bolt too much or it may break.
The washer used with the toggle bolt must be the type made to withstand hot water. Any other type will not last very long. After the toggle bolt is in place, fill the tank with water and see whether there is any leakage around the washer.
There are several patented devices on the market which may be used for stopping up leaks in tanks. in principle, they are all more or less similar to the toggle bolt and washer and, in most cases, will give good results.