We have a Water Furnace Premier 2, 6 ton unit , IntelliZone and 7-200 foot wells. The system was installed in 2000 and has function as expected. Recently one of the pumps went out on the flow center and the entire flow center had to be replaced. The flush cart was brought in to flush the system for about 2 hours. None of the Environol antifreeze was filtered during the flush. The flow center now gurgles on start up and continues but less after about 20 seconds, both pumps where burped. I asked the tech and he said this was normal. I don’t recall the old flow center sounding as loud as the newly installed unit.