I have a question about propane on the RV. We are currently using a small portable tank, like one for a gas grill, instead of the big tank on the RV. Can the regulator on the big tank be used on the small portable one, or do we need to purchase one specifically for the small tank? We are only using propane for the hot water tank. Don't want to use big tank on RV until we have a chance to replace it since it is "very" old, 28 years old to be exact, and is a Ford Midas Class C. Don't peticularly like the big "whoosh" we get when lighting the hot water tank for shower-time. Any suggestions or advice will be much appreciated.