Galvanized steel potable water supply and distribution pipes are commonly found with nominal pipe sizes from 3?8 inch (9.5 mm) to 2 inches (51 mm).
All such work can be carried out also by plumbers self-employed.You just have to reckon with the fact that the services contract with an independent plumber probably will prolong the work carried out.
However, this should not affect their quality, and sometimes it turns out that the plumber running his own business applies doubly to perform the outsourced tasks themselves.
Plastic pipework is used for the conveyance of drinking water, waste water, chemicals, heating fluid and cooling fluids, foodstuffs, ultra-pure liquids, slurries, gases, compressed air and vacuum system applications. Plastic pipe systems fulfil a wide variety of service requirements.
Product standards for plastics pipe systems are prepared within the standards committee known as CEN/TC155.These requirements are precisely described in a complete set of European Product Standards for each application alongside their specific characteristics. For example: Conveyance of drinking water: Hygienic requirements Conveyance of gas: Highest Safety requirements Plastic pipes for radiant heating and floor heating: Temperature resistance over decades Sewer applications: High chemical resistance. Plastic pipes are perfectly capable of fulfilling the specific requirement for each application.
For plastic pipe products, these levels are closely defined by the different standards.Źródło: https://en.wikipedia.org/wiki/Plastic_pipework.