The type of materials that are used in the growing system is very important, especially when you are growing wasabi.
As I have said before, wasabi must be grown in drinking water, and that requires that all materials that are in contact with that water are also approved for use with drinking water with a few extra additions.
The use of ferrous and non-ferrous materials on a wasabi farm is completely out of the question unless the non-ferrous material in question is stainless steel, and then grades 304 or 316 only. These are the material grades used for stainless steel water tanks and piping. All types of pipe fittings and controls can also be found in stainless steel. It should be borne in mind that this equipment is expensive, but will last a lifetime.
Plastic piping and fittings are commonly used in house and commercial building projects. They can also be used on a wasabi farm, but once again it must be approved for potable water and NOT sewage or waste water. Sewage or waste water piping is cheaper than potable water plastic piping, but they also leach chemicals into the water which will kill the wasabi plants. When you realise that, it does not make any sense to try to use these cheaper options.
Never use copper or steel piping (galvanized or plain) as they will also kill the wasabi plants.
The size of piping used on a wasabi farm commonly varies between 2 inch (50mm) to 12 inch (300mm) diameter pipes. Each size is used for a different purpose and the quantities required will depend on the design and layout of the wasabi growing area.