get a 2litre 1/2 gallon container wash it out, then fill the container completely full. send it to a lab that tests water, you want a test that tests TDS, PH, turbidity. there are two others but the important ones are PH & TDS.
drliu. both problems are related, it is your Anode that is giving you trouble & the short longevity of the HWS is normally a result of the anode.