<p>The heater has a liner for reception of an amount of water to be heated. An admitting pipe and an outlet pipe communicate with the linear in order to transfer the water flowing into and out of the linear. One of the admitting pipe and the outlet pipe has an internal thread. A heat source is provided for heating water in the linear. A pipe connector has an insulated main body and a metal connecting pipe integrally molded with the insulated main body. The metal connecting pipe has external thread that fits the internal thread.</p>
