What is the minimum diameter required for a valved drain on a boiler?

The minimum diameter required for a valved drain on a boiler is 3/4 inch. This size is typically chosen to ensure that liquids can drain effectively and efficiently from the boiler without the risk of clogging or slow drainage, which could lead to operational issues. A 3/4 inch diameter allows for adequate flow rate, which is particularly important when dealing with larger volumes of water or other fluids that may need to be drained quickly during maintenance or emergencies.

Using a diameter that is smaller than 3/4 inch could increase the risk of blockages and reduce the system's ability to remove water promptly, potentially leading to safety hazards. The standards governing plumbing and boiler installations emphasize the importance of having appropriately sized drains to maintain the proper function and safety of the system.