Common feed methods include the use of chemical solution tanks and proportioning pumps. In general, boiler treatment chemicals (polymers, phosphates, chelate, caustic) are added directly to the feedwater at a point after deaeration but before the entrance to the boiler drum. Certain phosphates (ortho-type) should be fed into the steam drum of the boiler. The chemicals should discharge in the feedwater section of the boiler system so that reactions occur in the water before it enters the steam generating areas. Chemicals added to react with dissolved oxygen should be fed continuously into the deaerator neck or below the waterline in the deaerator storage section. Similarly, chemicals used to prevent scale and corrosion in the feedwater system (caustic, organics) should be fed continuously. Chemicals used to prevent condensate system corrosion may be fed directly to the steam, feedwater or boiler, depending on the chemical used. Continuous feeding is always preferred, but intermittent application may suffice in some cases.