yes.. tap water. How much does your Iron cost? If it's anything like mine it costs about £20. I replace it very 2 years...Much cheaper than buying distilled water
It depends on what areas you live in. We have fairly soft water in Manchester and it tends to create scale fairly quickly. If you're living in a hard water area you should be able to use tap water without any problems.
Yes it's definitely the other way round. We have soft water and have never had a kettle furring up or trouble with a washing machine. As for using anything but tap water in the iron - you're having a laugh, aren't you?