Can the temperature and pressure (T&P) relief valve be used to vent a domestic hot water tank before flushing?

Yes, but it should only be used with caution. The preferred method is to open a nearby hot water faucet to let air into the system and break the vacuum. While the T&P relief valve can be used to release pressure or air, scale buildup can prevent it from reseating fully after use, leading to leaks. If this method is used, the valve should be checked afterward to confirm it has closed properly and isn’t dripping. Always wear appropriate PPE and stand clear of the discharge line during operation.