We draw water from a well into a holding tank and hot water heater. Over the last month or so, occasionally when I flush the toilet, the water stops and I hear a popping sound (like the sound of popping bubble wrap) coming from the general area where my holding tank and the hot water heater are located. The water stops flowing. After a minute or two, the popping stops and the water flow resumes. The popping doesnt seem to relate to hot water use, though, as other posted questions here do. What could it be? Should I be concerned? Thanks Greg