466 APPLIED SCIENCE 



556. Joints. The joints most commonly used by plumb- 

 ers are the wiped and screw joints. The wiped joint is 

 made by scraping and fitting the parts together and then 

 pouring molten solder upon the place of joining. This 

 solder, while still in a plastic condition, is wiped around the 

 joint, with a moleskin or cloth pad. Thus a neat and re- 

 liable connection is made. The screw joint is made by cut- 

 ting threads upon the pipes with stock and dies, painting 

 the threads with white or red lead to make the joint tight, 

 then turning each piece of pipe half through a coupling by 

 means of pipe wrenches. 



557. Cement. Plumbers use a mixture of one part 

 Portland cement and two parts clean sand over a ring of 

 oakum in making joints on earthenware house sewers. 



Questions 



1. Describe the importance of plumbing. 



2. State the advantages of a good water supply. 



3. Name the different sources of water supply. 



4. How does water reach a well? 



5. Describe a water system of a city. 



6. How does water enter a house from the street? 



7. Is the flow of water on the top floor as good as on the first 

 floor? Explain. 



8. What is a faucet? 



9. What is water hammer? 



10. How is the waste water disposed of? 



11. What is a trap? State its advantages. 



12. Describe the work performed by a plumber. 



* Oakum is prepared from old ropes, untwisted, loosened, and 

 picked to pieces. The material is then treated with tar to make 

 it flexible. It is used in calking the seams of vessels, etc. 



