Range boilers or hot water storage tanks are made of either galvanized steel or copper. Galvanized steel is subject to internal rusting in time and must be replaced when the condition becomes serious. Copper, on the other hand, while more expensive than galvanized steel, will last almost indefinitely.
The tank must be large enough to hold, an adequate hot water supply. If the tank is too large for the amount of hot water required, move the cold water pipe from the tank to heater higher on the tank to reduce the quantity of water heated and prevent excessive consumption of fuel.
The storage tanks used for automatic gas and electric heaters are provided with a safety valve in addition to the mechanism controlling the heating element. Other types of heaters may or may not have a safety valve, but it is a good idea to have one installed, regardless of the type of heater.
These valves are placed at the top of the tank and connected to a length of pipe running to the floor. If the tank overheats and steam is blown off, it will run down the pipe into a pail or onto the floor of the basement and not splash over walls and ceiling, or possibly a person.
In a home where the hot water system has not been installed correctly, the hot water, on reaching a certain temperature, will occasionally back up into the cold water line. This condition can be remedied by having a valve installed on the tank.
Dirty hot water
Nearly all water, regardless of the source and treatment by purification plants, will contain some sediment which will eventually settle at the bottom of the hot water tank. Combined with this sediment will be rust from the pipes and tank—should they be made of galvanized steel. Note that on a well-designed hot water system, the cold pipe from the tank to the heater is connected several inches above the bottom of the tank.
This positioning of the pipe allows the sediment in the water to settle at the bottom of the tank, where it is only slightly disturbed by the circulation of the water. The sediment will accumulate in the tank until it flows through the cold pipe into the heater and thence into the hot water pipes throughout the house. Most tanks are equipped with a drain valve at the bottom of the tank, and opening this will remove a large part of the sediment.
Do not use any hot water for several hours, to allow the sediment to settle at the bottom of the tank. Open the drain valve and allow the water containing the sediment to flow out of the tank into a pail or some other container. It is not necessary to drain all the water in the tank—drain until the water runs clear. If the water in your community contains much sediment, drain the tank at regular intervals to ensure clean hot water.
If the cold pipe is connected to the bottom of the tank, there will always be some sediment circulating through the hot water system, as there is no place in the tank for it to settle. Placing the cold pipe higher on the tank will correct this situation.
The coils of a heater will collect sediment, and this can be flushed out by disconnecting the pipes and attaching a garden hose to the coils. The sediment will be forced out by the pressure of the water.