Water hammer

[Tomsic]

The water hammer arrestors are a good fix for the problem. I've had one on the cold water line near the main house valve for 9 years now with no problems and no water hammer. But, having said that and reading your original post again, the likely culprit is the toilet water valve. Since you didn't change any plumbing when the hammer started, it has to come from wear and tear or some kind of system change such as a change in line pressure. I'll vote for a worn toilet water valve that sets up an oscillation in the tank.

Tomsic

[DerbyDad03]

re: "it has to come from wear and tear or some kind of system change such as a change in line pressure."

...or the leaching out of the air in any air gaps that might exist.

Oft times, simply draining the system and then refilling it will put the air back into the air gaps and the problem will go away for many years.

Been there, done that.

[DD_BobK]

Not in my experience.....

I have a house built in 1930 that originally had galvanized steel plumbing, complete with 12" to 18" air chambers which never worked very well.

The 85 psi water pressure delivered to the house via a 1" copper line might have been the problem.

Since the house was re-piped with PEX and had the following added... double check valve pressure reducer water hammer arrestors on toilets, washing machine & misc other locations

no more water hammer.

cheers Bob

[Steve Barker]

lowering the pressure on the old system would have worked wonders also.