Purchasing a new trailer for our site, it has an "on demand" water heater in it, normally we would use the showers up at town hall due to our old trailer having a small tank heater and a small shower, ad as stated the new one has a "on demand " water heater and a nice walk in shower so plan on using it. Question... being a tankless heater and the fact we are on well, Is it a good idea to use an external water filter to prevent any build up that may occur in water heater? I have been looking and there are types that are self contained and then there are ones with replaceable element, looks like some of the ones that have replaceable elements actually remove dissolved heavy metals, and reading some feedback on self contained filters, you can run the risk of mold forming and most do not list that they remove heavy metals. Has any of my fellow JD'rs tried or use any of these products? the good? the bad? and ones to stay away from? Thanks!!!