Gas boilers are central heating systems that use gas to heat water to be used around the home. Heated water from the boiler is transported to radiators to keep the house warm and also to taps to provide hot water. Heated water can also be pumped to a hot water tank and stored for future use. There are different kinds of natural gas boilers. Firstly, combi boilers are a form of gas boiler that does not involve water storage. On the other hand, system boilers do involve the storage of hot water in an insulated tank in addition to another cold water tank. Then there are also regular gas boilers which are similar to system boilers but can be vented or unvented.