I live on top of chalk hills (The Chiltern Hills in England - northwest of London) and our water is extremely hard. I've never had problems with graininess on ISO 100 or 400 films. TMZ 3200 was grainy though ... not unexpected. The only thing I do have to do is to use a wetting agent, otherwise I'll get chalk streaks all over (Ilfotol is my usual).(posted 8970 days ago)