First of all, don't admit this to immigration authorities at the border force. If they know you intend to work (or caught working) on a holiday visa they can deport you and ban re-entry for about 5 years.

You need an employment visa to work here, not a holiday visa. Nowadays it isn't easy, but pipe relining (or an associated industry you can work in) seems to be one of those jobs on the skills-shortages list.

If you manage to find that, qualify and apply (hundreds/thousands of dollars plus several months of paperwork and organising things) then you might need accreditation because skilled professions are only really mostly transferrable from English speaking countries like UK and Canada. To be qualified, you would most likely have to go to a TAFE which is a vocational college.

It's through TAFE that you will find an apprenticeship, which leads to a full time job. Keep in mind though that Australia and Australians can be quite parochial, so don't be surprised if they keep rejecting you and you spend months or even years without work.