A Query.

This has irked me all day.

Why do water tanks have corrugated sides??

I watched a truck with water tanks for delivery, & remembered all the tanks I have seen - & they are many, being the latest necessary accessory for a house, because of the water crisis we currently have...(mainly due to short sighted planning...oops, I will probably be arrested for that!)

I suppose there must be some website I could go to, where all would be revealed.
But that is not as much fun, is it, as asking friends on the Internet???