Most likely.
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.
Water hammering on any quick closing valves
When the steam hits colder piping it turns to condensate and the steam hitting the water (condensate) produces hydraulic shock waves.
It does things to the things in the things the pipes are made out of if you get me
Any break or leak on the suction side of your pump can cause air in the lines.
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.
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.
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.
Water Hammer.
Water hammering on any quick closing valves
When the steam hits colder piping it turns to condensate and the steam hitting the water (condensate) produces hydraulic shock waves.
Yes. Both caustic and acid based drain cleaners can do damage to your metal pipes. Instead, you can try an all natural remedy of pouring baking soda down the drain followed by vinegar.
Burst water pipes and water heaters busting are covered for the damage caused inside the house if its sudden and accidental, but the pipe or water heater themselves are not covered as this is maintenance. This is generally not a problem as the damage is more severe than the piece of pipe. Outdoors is going to be more of a problem as the damage is nothing anyway. More information is needed to give you a complete answer. Are you talking about sprinkler system, pipes in a pool house for the pool, or other pipes. Cause is the issue in question as well.
Lead (and copper).
A common cause of pipe noise in a home is when the pipes vibrate or rattle inside the walls. When the home was built, the plumber is supposed to install strapping around the pipe where it enters the studs in the wall or travels through the floor to prevent this. If this strapping was not secured and has fallen off (or never there to begin with) this will cause the pipe to rattle or vibrate when the water is turned on or off and cause the noise you are hearing. I don't think it is cause for alarm, but it definitely is annoying. Repairing this problem could be simple if the noise can be pin pointed. A licensed plumber should be contacted regardless.
If your pipes freeze and burst, the damage could be extensive, and the repair could be costly. If your home has exposed pipes, wrap them in heat tape. That way, when the weather gets very cold, the heat tape will warm the pipes and keep them from freezing. Even if your area does not usually have hard winters, make sure to protect your pipes just in case. You could have an unusually cold winter. Remember to insulate any pipes in your garden as well. These pipes can cause damage if they freeze, even if they are far away from your house.
To protect them from frost damage. In cold weather, 'standing' water in cold pipes can freeze if the temperature drops low enough. When water turns to ice, it expands - which could cause the pipe to burst. However - you wouldn't know if it had burst until the ice had thawed !