(a) organic polyelectrolyte combined with anti-foam minimises scale and foaming, it can be used in evaporators producing water for drinking purposes (DTp). It would be continuously fed into the feed line by a metering pump (to ensure overdosing does not take place) at 1-8 p.p.m. of evaporator feed, the rate depends upon evaporator density and output.The compound is alkaline and should be treated in the same way as caustic soda; it should not be taken internally. (b) Polyphosphate compounds with anti-foam prevent the formation of calcium carbonate scale and minimise possibility of foaming. The is compound non-toxic, non-acidic, relatively cheap and safe to handle The DTp powder. allows it to be used in evaporators producing water for drinking purposes if the dosage rate is 2-4 p.p.m. ofevaporator feed. It is suitable for low-pressure only plants. At temperatures around 100°C it forms a sticky grey sludge. It should only be used at temperatures below 90C.