PLUMBING AND WATER SUPPLY 467 



13. Name some of the common plumbers' tools and their uses. 

 State the mechanical principle upon which each of these tools 

 operates. 



14. What is a joint? Why is it used? 

 16. Name the common joints. 



16. State the conditions under which a plumber works. 



17. What per cent of clean sand is used in making joints of 

 earthenware house sewers? What per cent of Portland cement? 



