Homeowner has Bradford White S#WE45219528 (50 gallon gas direct vent) water heater. Existing ST-5 expansion tank. Water pressure per my gauge is 75 PSI. Per expansion tank sizing chart the ST-5 is acceptable for this application based on pressure and the temperature setting. Homeowner has water heater set at “factory setting” which is about 110 degrees to 120 degrees. Any setting above 160 degrees would require the ST-12 for 50 gallon. Preventative maintenance ac system. Homeowner replaces own (20x20x1). He has (3) filter grilles in the home. He maintains filters on a schedule. Coil inspection, gravity drain draining properly, amperage check on ac related components and 410a refrigerant charge verified correct. 17.2 degree delta T reading. Left IAQ recommendation. Has had duct cleaning performed by Chud and heater maintenance.