Electric welding. They have special heating elements made of wire in their design. Such bounces are made by welding, so their use is limited. Today they are used mainly for hot water supply. Among the advantages, quite cheap production can be noted, as well as the simplicity of installation. But they have one significant minus that blocks all the advantages — they have welds, which is not a virtue for the water supply. With a sharp drop in pressure and temperatures, cracks often form in such a challenge. Когда кто-то видит фонтан воды из-под канализационного колодца — скорее всего, это прорвало электросварную трубу. However, the low cost is still attractive for construction companies.