An apparatus for automatically feeding soda ash or other precipitating chemicals to hard water is shown in Fig. 121. This apparatus is used in connection with waterbacks and water heaters to prevent them becoming choked by deposits of lime. When properly looked after an apparatus of this kind will precipitate so large a quantity of the lime or magnesia held in solution by the waters, that the periods between cleanings of waterbacks or heaters will be lengthened from 50 to 100 per cent.

Fig. 121

The precipitating reagents are placed in this vessel, wetted, and the two valves opened sufficiently to give a flow through the apparatus proportioned to the amount of water flowing through the pipe. The apparatus then works automatically until the chemical reagent is exhausted. To secure satisfactory results the apparatus must be placed on the return pipe to the waterback as shown. All water is thus treated before reaching the waterback or heater.