There are the typical blockages, and then the very unusual. I have seen many strange objects in obstructing the flow of a drain. A brush, from household dust pan and brush, large sections of brick (half a brick), building rubble, sand, stones, children's toys, bottles, a measuring tape, a car oil filter .... etc. The list could just go on and on.
Never use Drain-o or Caustic Soda chemicals to clear blocked toilets or the outside drains. It will not clear the obstruction, it will increase the danger of chemical burns to a technician and damage clearing equipment. All the drains are connected together, so if more than one drain is blocked, it is likely the drains outside are blocked.
All drains are designed to carry water, and water only. And there are several reasons a blockage may arise.
Hair and sludge from soap, shampoo, body fats combined are a common cause of blockages in showers and hand basins. This can be simply removed with a smaller machine.
Tree roots require an entry point into the drain. Ground movement and/or, roots putting pressure on the pipe until it cracks, or a pipe joint which was not sealed completely upon installation is very common. A cracked connection from the waste pipe to the large drain pipe is often a point where tree roots enter the drain, or tree roots can blocked the main drainage pipe outside, not allowing the water to empty from the sink. The only permanent remedy is to seal the roots entry point. In some cases will require a section of the pipe to be replaced.
In older properties which still have the original galvanized steel waste pipes, the pipe is corroding on the inside of the pipe. As the rust expands inside the pipe, the inside pipe diameter becomes much smaller and the rough rusty surface allows for material flowing down the sink to become caught. These older pipes can be a continual source of problems. Never use a caustic soda or drain-o products on properties with metal drains. It will speed up the rusting process, leading to more blockages and the need to replace them much sooner due to the pipe rusting through completely.
For assistance with plumbing and a blocked shower, please call 0414935499