Abstract: A tube connecting element of plastic for sanitary and heating purposes, has two connecting sleeve elements each having a bore, which bores are in alignment with respect to one another so as to form a common flow through bore, and into which plastic tubes may be welded. The tube connecting element has a sleeve body between the two connecting sleeve elements and forms therewith a united entirety. The sleeve body is provided with a bore extending perpendicularly to the common bore of the connecting sleeve elements and serves for the reception of a third plastic tube. The common flow through bore connecting the two bores of the connecting sleeve elements is offset with respect to the center line of the two aligned bores in the direction of the outer wall of the T-configurated tube connecting element located oppositely to the perpendicularly extending bore.

Abstract: A plumbing and heating pipe system for water supply purposes, made either completely or mainly of plastic material, especially of polypropylene, said system being provided with metallic connecting sleeves as well as reducers for connecting the plastic pipes to fittings of metallic materials, and being provided with shut-off valves made of plastic material and having a plastic-encased metallic valve seat for mounting in pipe lines, and being provided with pressure-type screw connections for the pipes to be joined to each other and with reducers for connection to radiators, wherein a welding device having an arrangement for equalizing the lengths of the plastic pipes is used to weld parallel plastic pipes.