The purpose of boiler blowdown is to control solids in the boiler water. Blowdown protects boiler surfaces from severe scaling or corrosion problems that can result otherwise. There are two types of boiler blowdowns continuous and manual. A continuous blowdown utilizes a calibrated valve and a blowdown tap near the boiler water surface.
Check the water chemistry. In every modulating condensing boiler installation instruction manual you will be given parameters for the proper water chemistry of the fill/makeup water. And if youre not testing youre guessing. Test kits are readily available as well as the ability to send out a water