Nothing foolproof but I would start by activating them manually. Usually
there is a thumb screw or the solenoid unscrews partially then the water
flows without the controller activating the valve. Look for the word Open
and an arrow on the valve.

Put your hand on the valve, you should be able to feel and hear valve
chatter once you are that close.

Not sure what kind of defect to expect, something that causes oscillation of
the valve under certain pressure conditions. some debris caught in the
valve? Rubber parts are notorious for causing noises especially diaphrams
and valve seals

Any leaks after this valve would just appear like a sprinkler head to the
system, it would not cause thumping.

Also try adjusting the main supply valve, make sure it is all the way open.
It may also be a source of noise. Since you have the same thump on 3
branches of pipe, it may very well be this or something common to all 3


"shibumi" wrote in message
ps.com...
Is there any way to test the zone valves or solenoids - w/o having to
replace them?