I have rust in my well water. It is a 100 foot well with 17 feet of casing. It has been there for 35 years, most ot this time the rust has been present. It is not visiable only in the toliet bowels if the water stands for a time. I have put on a rust filter and it stops most of it. I suspect it is comming from the casing, which I see is listed as a possible cause. If this is the problem I guess the only answer is new caseing but what will stop it from happening again?