A.Dave Yates, a plumbing contractor in York, Pa., responds: The placement of the tank and check valve are fine; that ticking sound you hear is coming from thermal stress taking place in the expansion tank as it accepts expanding water.

This problem is likely to be more noticeable during the heating season because that's when there is the greatest difference between inlet and storage temperatures: The greater this difference, the larger the volume that the TXT (a thermal expansion tank rated for 150-psi maximum working pressure and potable water) must accept.

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