I don't recall seeing that recommendation in the Colonix package insert or on their website. Is that a recommendation from your healthcare practitioner? Do you have liver issues that cause pain when you eat fats? We need fats in our diet to make bile to digest our foods as well and produce hormones.
Organic butter, ghee (clarified butter), olive oil or virgin coconut oil would be better choices than margarine.
"Virtually" trans fat free means there is trans fat in the product, otherwise they would be able to claim "trans fat free". Don't be fooled by the marketing rhetoric.
Whether you need to drink filtered water or use tap water is a factor of where you live. When I lived in a small mountain town I could drink the tap water. I now live in a metropolitan area with a history of industrial and agricultural chemical usage, so we only use filtered water and have filters installed on the shower heads in the bath. Our tap water tastes "dusty"! (Interesting quality for water, don't you think?)