A boiler drain can usually be found on a boiler and the surrounding pipes. As the name implies, a boiler drain is used to drain the boiler and pipes. They are also used in other parts of the home and building. As a master plumber, I have seen them used as washing machine valves, utility sink faucets, and even as outside faucets.
When a leak develops on a boiler drain, repairing or replacing it can be problematic, especially if the valve is a part of your heating system. In order to repair or replace a boiler drain, the water will need to be shut off and at least partially drained. This is not the problem. It’s when the water is turned back on and the pipes refilled that the problem emerges. Air will form in the lines, and air can cause big problems such as pipe banging and improper heating in a hot water heating system. The pipes will need to be purged, which can be a difficult process and may require contacting an experienced heating professional.
So how can you fix the drip without shutting down, refilling, and purging the system? A boiler drain cap works very well in this situation. Many plumbers, faced with draining and refilling a maze of old heat pipes or a boiler the size of Cadillac, will use a cap to stop a valve leak. It simply turns onto a boiler drain threads. Because there is a rubber washer inside the cap which keeps water from passing through, the threads do not need to be taped. The cap does not need to be too tight, just snug. I’ve used boiler drain caps in my own home, and the beauty of them is that you don’t need to be a master plumber to stop a leak with them. Anyone with a pair of pliers can use them. For a homeowner who doesn’t want to pay hundreds of dollars to a professional to stop a drip, a boiler drain cap is a great short-term solution.