Speed up the replacement of water with air by opening the vents (bleed valves) at the top of each radiator. Thanks for printing! don't forget to come back to delta plumbing for fresh articles! I am so impressed with your product! i had a backed up shower drain which was miserable i (embarrassingly) tried draino first, and it did nothing! i used drainbo, and immediately the shower improved, but the drain was still slow however, every time i use the shower.