When the steam hits colder piping it turns to condensate and the steam hitting the water (condensate) produces hydraulic shock waves.
Pipes rattle when heat is turned on because metal expands when heated up
Most likely.
Water hammering on any quick closing valves
choir members in your pipes
Do your pipes freeze .
I don't even know what a recirculating pump does but when fast moving water hits a corner or elbow it has a force that can move the pipe. Most likely the pipes need a bit more tie downs. Hopefully the pipes aren't in the walls. Get someone to cut the water on and you go hunt the rattle.
High water pressure could be the reason for pipes to rattle when you turn on the outside sprinklers. You may need to have a reducer valve installed.
Singing water pipes can be caused by air that is trapped in the pipes. The air can cause a whistling or singing sound, or it can cause the pipes to knock or rattle.
Most likely.
Water Hammer.
I'm not familiar with rumbling in pipes, but the clanking of pipes when the heat starts up is a result of the pipes expanding because of the heat. Heat causes the metal to expand slightly, and the joints creak and clank when the heat makes its way through the pipes.
Water hammering on any quick closing valves
Hammering pipes is the result of inertia when moving water causes the pipes to move when a valve is suddenly turned off. Use an anti-hammer device. You can purchase one at most home centers.
choir members in your pipes
yes, as they heat up or cool down they groan
the heater matrix is blocked
Heat tape is just for keeping the pipes from freezing, it does not heat the water. That's what the hot water heater is for.
The purpose of heat tape is to maintain and control pipes and vessels. This also keeps the heat that is being radiated from the pipes and vessels inside.