The case of the banging steam pipes, this week's case

In this case, I was called because they were having pipes banging. Inside the boiler room was a cast iron sectional boiler with three zone valves. The zone valves were connected to a thermostat in each zone. The valves had an end switch which would enable the boiler. The banging only occurred when one zone was started. The installer had a steam trap so no water would lay against the seat. I will reveal what I found on Friday morning.