A plumber is a tradie who specialises in water and sewage piping. A plumber can fix leaking pipes or install a new hot water cylinder.
Yes, plastic plumbing piping is becoming increasing common in domestic plumbing jobs. The pipes are cheaper than using metal and are quicker to join and use as they do not require brazing together.
The price of copper has risen dramatically in recent times and thus has led to a decrease in its usage in plumbing jobs.
Yes, if you employ a plumber you will want to check that they are licensed to operate in your state. Each state keeps its own licensing and registration scheme. If you ask a plumber for their licence number they will be able to provide it for you to check.
Yes, a plumber can install a hot water system for your house. If it is a new electric hot water system you may also need to get an electrician invloved to connect the new system to your power board.