We’ve a 40 your house. Air in the pipes causes a chunk-chunk-chunk sound when the toilets are flushed.
There are procedures on line for turning off the main water at the street, opening all the faucets, turning on the water main and then closing the faucets in a certain order to flush out the air.*** These procedures work!***
But - a few months later the sounds return.
Short of paying a professional is there someway to find out how the air gets into the pipes and prevent a recurrence?