You can boil water not only with a boiler. In addition to heating water on an electric stove, gas stove, boiling it in an electric kettle, other methods of obtaining boiling water are used.
Hot water can be obtained from a cooler - a modern installation for supplying cold water for drinking and hot water for brewing coffee or tea. Such coolers are often used in offices, work establishments, but now they can be found very often in home use.
Boil water over a fire, without a boiler or electrical outlet. To get boiling water, tourists make a fire in nature. A semblance of a barbecue made of bricks or stones is installed around the fire. A kettle is placed on top of the device, the water in which heats up quickly. You can hang the kettle over the fire. For this, two holder pins are installed on the side of the fire. They are connected to each other by a third pin, on which the kettle is hung by the handle. The kettle is directly over the fire. Thus, the water in it boils.
In Soviet times, without a boiler, they resorted to a home-made device, which is still in demand today. To make this homemade kettle, take a pair of razor blades. They can be replaced with two pieces of metal sheet without rust. The size of the pieces should be similar to razor blades - 2 cm wide and 3 cm long.
You will also need a two-strand insulated wire connected with a plug at the end. Attach blades or pieces of sheet metal to the ends of the wires. Attach a few matches or wooden sticks between them through duct tape to isolate the blades from each other. The device is ready.
When such a device is connected to the mains, the current will pass between the plates and will generate heat, which will soon boil the water. This is a rather dangerous device, therefore, when applying it, you need to adhere to certain rules.
Only boil water in a glass, jar, or earthenware with a homemade boiler to avoid cracking the boiling water. While the water is heating up, do not put your hands in it, as an electric shock is possible. As soon as the water boils, disconnect the device from the mains. The water that you boil in this way must be potable, not salty. And it is impossible to salt water with such a boiler when boiling, since most of it will splash out.