I recently had some piping work done to my gas boiler system. This required draining and then refilling the system. The result has been introducing new water to the closed system and a new popping sound when the boiler is running. This sound travels throughout the heating system whenever the boiler is heating. My boiler tech says that the sound is mineral deposits in the boiler becoming active when heated. The popping sound is only heard when the boiler is heating (the heating season is upon us). He indicated that draining the system and refilling it would only solve the problem temporarily and the sound would return. The boiler is 17 years old and has a mineral build up that cannot adequately be removed without completely removing the boiler and cleaning out the lower portion below the drain. He is suggesting the addition of one to two gallons of glycol. While this will reduce the heat transfer to some extent, it will also reduce the amount of mineral deposits becoming suspended in the boiler eliminating the popping sound. Is this method the best low cost option available to me or are there any other suggestions that I might consider save replacing the boiler?