THB DAIRY HOUSE 135 



ing pipes. With a good valve of this kind a pressure 

 as low as one pound may be carried when the boiler 

 pressure varies from twenty to fifty pounds. 



Screening. Where proper sanitation is expected it is 

 absolutely necessary to guard against flies, and this can 

 easily be done by screening all doors and windows. Flies 

 are a prolific source of milk contamination and must 

 therefore be rigidly excluded from the dairy. 



