A "chemical heater" in the form of a cartridge containing an exothermic agent such as sodium hydroxide (caustic) soda, or the like, which, when infused into water, releases heat in the form of an exothermic reaction. In the preferred embodiment of the invention, a cartridge is provided which contains the exothermic material. Water or the like is then directed through said cartridge so that the exothermic material dissolves, providing a solution of water infused with the exothermic material. The solution is heated by virtue of the exothermic reaction, said solution passing out of the cartridge and into a bladder located in a pipe, filling same. Situated about the bladder is a patch or sleeve of material including heat cured resin, which is urged to line the pipe by virtue of the bladder inflating, while simultaneously heated to cure same by virtue of the heated solution. Upon curing of the resin, the bladder is deflated and the fluid drained or otherwise disposed of, with the cured resin sleeve or patch remaining in place lining the pipe. The bladder may then be removed. An alternative design of the invention teaches a bladder configured to receive the exothermic material, allowing the bladder to inflate and provide an exothermically heated solution to heat the bladder simultaneously.