A technique of welding into the socket in polypropylene pipes at low ambient temperatures is offered. The tests of welded socket joints made with different welding modes are carried out. It is shown that the short-term testing methods of the quality of welded joints of polymeric pipes existing in the normative documents do not reveal a violation of technological modes of welding into socket. Quality of welded joints is estimated by tests on a long stretch in the environment with surfactantt. It is established that the proposed welding technology into the socket of polypropylene pipes at low ambient temperatures provides the required level of quality produced for welded socket joints.