hot water tank noise

I had an earlier post about water tank noise. Not the typical deposits build up noise. This was a rattle for about 3 seconds about every 10 seconds this would accrue pretty much non stop. Plumber sent out by home warranty Co. could not figure out. Thought it was excessive pressure. But he did say one thing the dielectric nipples in the tank had check valves. Well when he left I checked the pressure 60 PSI behind regulator (plumber did not have a gauge) so I had a set of dielectric nipples without check valve, problem gone. The check valve is nothing more than a marble in the plastic sleeve with a stop. I myself have never seen these before nor do I want to see them again. Any way just thought I would share that.
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