Because many houses still have the older hot water heaters, they are also mentioned here. These days, boilers will be the ones purchased.
The methods of heating hot water include:
When planning your hot-water system, you must decide on how much hot water you will need. A good rule is to anticipate using slightly in excess of 25% of the total daily consumption in your home. Your tank should be large enough to provide that amount, but small enough to prevent costly wastage of fuel.
Hot-water tanks can be installed either horizontally or vertically. They must, however, be above the heating element to enable the heated water to rise and circulate in the tank. Most residences have vertical tanks, the horizontally installed tank being generally confined to large apartment, office, and factory buildings. Every tank should be equipped with a drain valve at its base, and a safety valve near the top to prevent possible explosions in case of overheating or the trapping of steam. The amount of cold water fed into the heating element from the main is controlled by a valve placed as close as possible to the heater. If the water is heated and stored in the tank, it is fed into the top, but the inlet extends to the bottom so that the water will rise to the top when it has been heated, preventing co-mingling.
The distribution of the hot water throughout the system is usually accomplished in one of two ways. The first is the direct or non-circulating system in which the hot-water pipes run directly to the fixtures from the source. The second, is the circulating system. This consists in a central pipe which carries the hot water to the general location of the fixtures and an additional pipe which carries unused hot water back to the tank. Water is carried off the central pipe by branches to the fixtures themselves.
The circulating system is based on the fact that hot water tends to rise and cold water tends to fall. This principle, as it applies to plumbing, can be stated as follows: The heated water rises of its own accord until it reaches the highest point in the system There, the water cools and is forced by the hot water behind it into the parallel pipe which returns it to the heater, where the process starts all over again.
The object of the circulating hotwater system is to maintain a continuous flow of hot water which can be drawn off at any point. Sometimes known as the "upfeed and gravity return!" system, it is preferred for smaller residences. Although it is more expensive than the simpler direct system, it provides more heated water and eliminates the need for pumping mechanisms.
Connections for hot-water heaters
Making the connections for your hot-water heater or the storage tank is the same as making connections within the piping system itself. In a way, the tank or heater can be considered to be similar to a length of pipe connected to other pipes by fittings. Of course, your heater or tank is an item of some weight and size and must be supported in a way that will keep it in place securely. Vibration and movement is especially dangerous in a hot-water tank, as scalding or injury could result should it break away.
You must also consider the means by which the water is to be heated. In some cases, heat is supplied by the central heat source, such as the house furnace. In others, either gas or electricity may do the heating.
Regardless, of the type of tank or heater, there will always be two major pipe connections, the first being the inlet for the cold water, and the second being the pipe by which the heated water enters the distribution system. In the case of tanks with separate heaters, an additional loop of pipe is used to circulate the water from tank through heater and then back to tank.
With electrically heated tanks, no special connection for the electric wiring is made by the installer as this type of heater is manufactured complete. The gas heated tank will necessitate a connection with a gas source, using pipe and connections similar to those made in connecting a kitchen gas range.
Some tanks will be fitted with a faucet or cock for drainage purposes, whereas others will have only a drainage valve or a capped hole near the tank's base. It should be noted that the use of either a T or an elbow-bend depends upon the other connected pipe. If possible, the pipe from tank to cock should pitch slightly so that gravity may aid you when draining. Leave enough room under cock for a pail.
The typical gas or electric heater has a T attached to the hot water line at the top, to which is attached a safety or relief valve. If temperature in the tank should ever become too great, the line, which runs from this valve to the floor, permits the water that is overheated to be drawn off. In cases where water has a high lime content, the relief or safety valve is placed at the cold water entry pipe to prevent it from becoming clogged with the lime sediment.
There are at least 6" between the bottom of the tank and the draw-off pipe to the heater for settling of sediment and a drain cock so that this sediment collecting section can be cleared occasionally. Tappings are standard, making this type of connection excellent for either water-back or gasheated tanks.