PP-r pipes and fittings can be used to build complete internal tap water systems. Pipe sizes for tap water normally ranges in diameter from 16mm to 75mm. Pipes are rather thick and inflexible. Installations are made in straight lengths, using fitting for bends, PP-r pipe systems are used in PN-20 dimensioning according to DIN E 8077 for a maximum operating temperature of 60° C and maximum 10 bar pressure. For 70° C maximum operating temperature, a PN25 system is used according to the same standard and maximum 10 bar pressure.

In floor heating, hot water is conveyed through pipes laid under the floor. Since the heating surface is large, the water temperature can be lower than in radiators (30-60° C compared to upto 80° C). Floor heating gives a very comfortable climate. The best comfort level is reached with a floor temperature of 27-29° C (35° C in bathrooms). Small diameter pipes (typically 12, 16 & 20) are used in floor heating because of the larger surface per volume for easy installation. The smallest allowable bending radius is 6 times the outer diameter of the pipe to avoid buckling of the pipe.

Semi-mechanical fittings are injection molded with threaded metal inserts to allow for one-part mechanical joining, as adapter between metal parts and or/ other parts for socket-fusion joining to a plastic system. The metal part is often Ni plated brass.

Socket welding is an established method commonly used to connect tap water systems using PP-R. The external surface of the pipe and the internal surface of the fitting are preheated and the pipe is then inserted in the fitting, creating a fusion joint between the two surfaces. This type of welding can be carried out with inexpensive equipment. If carried out according to good working procedures, it should result in tight joint lasting the lifetime of the pipe system.

Electro fusion fittings are available in PP-r, although they are less commonly used than socket fittings. The electro fitting has a conductive thread incorporated into the wall. The fusion is performed by inserting the pipe ends into the fitting and applying an electrical current. The current heats the conductive thread, which melts the PP interfaces to form a fusion joint, Electro fusion is a safe method and easy to control.

Tests have been carried out using butt-welding and socket fusion techniques to evaluate the welding compatibility of PP-r grades. The mechanical characteristics and pressure resistance of the welded assemblies have proved comparable with unwelded material.