Many years ago a customer asked for our recommendation for material on a specific service, which we supplied. He then came back and asked us to double check our recommendation, which we did. After some time, he asked again, and we answered in the same way. Yet again, he asked the same question, but this time we asked him why he kept asking the same question. His response was, “well you keep recommending stainless steel, but we’ve been pumping this stuff for over 20 years with cast iron pumps.” On paper, the right material was stainless steel for that particular product, but practically, the cast iron was fine. The best answer comes from the experience of that product in that particular location. The second best answer will come from a reliable local supplier.