What causes a frequent vibration in basement area and seems to radiate through furnace and ducts, and water heater and pipes to septic system (which has an intermediate tank and pump)? Can't isolate the source of the vibration. The vibration is immediately stopped by flushing a toilet?

Lets see how far we can get on this.
Ways for duct to vibrate.

Unbalanced squirrel cage fan in furnace for forced hot air.
If duct vibrates and a water pipe touching it the water lie makes noise "water Hammer"

Water pressure in pipe released and then stopped and pipes rattle

Pipes Vibrate by a machine/ motor mechanically doing that.

Do you have a grinder sewage pump out side?

Do the pipes make noise when the well pump kicks on?
Need a bit more info on timing of sound when mechanical motors are on.

Signed 21 Boat

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