A boiler making banging sounds does not always mean it’s about to blow. It might be just asking for your attention. We’ll share with you some possible reasons for noise coming from your boiler; but it will be in your best interest to call a professional to diagnose and solve the problem.
Over time, air gets built up in the system and pipes. Locate the pressure release valve (or bleeder valve) for the system and s-l-o-w-l-y open to let the air escape. You will probably hear it hissing. Barring any other problem with the boiler, this should take care of the banging.
Again, over time, there could be some sediment built up in the system. The heating element is stressed while it’s heating up when there is sediment buildup. The element will create steam as it heats up the water faster due to the sediment; and the banging could be coming from the pressure of the steam.
You could have an expansion tank that has begun to fail and will need to be repaired or most likely replaced. Another place to look for the banging is with the zone valve. We recommend hiring a service technician to take care of these issues for your safety and peace of mind.