(56) Distinguish between coal gas, producer gas, and water gas.

(57) (a) Should gas pipes be run in places exposed to cold weather? Give your reasons, (b) If they must be run in such places, how should they be protected? (c) What must be guarded against when iron gas pipes run very close to electric wires? Where there is danger of contact, what provision should be made?

(58) (a) Clearly explain how ceilings may become discolored by gas flames, (b) How can the discoloration be prevented?

(59) Describe the star diaphragm of a photometer, and state its advantages over other forms.

(60) Distinguish between roll-rim and plain-rim baths. Which are the better? Give reasons.

(61) Describe the most efficient and most economical method of flushing a urinal, and explain its action.

(62) (a) What size of tank is required to supply a building having 60 occupants, assuming that the supply is taken, from street mains? (b) What size is required if the building is located in the country, and the supply is obtained by means of a hot-air engine?

(63) A 4-inch branch taken off the main house drain is continued to an ordinary half S trap with a grating on top, the grating being flush with the cellar floor. It is found that water from the sewer backs up through this trap during heavy showers and floods the cellar floor, (a) What appliance should be used to prevent this trouble? (b) Describe its operation.

(64) (a) What is the most desirable velocity for sewage in an ordinary house drain or sewer? (b) What is the proper fall to insure this velocity in a 4-inch drain pipe?

(65) A six-story building is supplied with water from a tank in the attic. Show by sketch how the distributing pipes should be proportioned so that each floor may have a uniform supply of water.

(66) (a) State the properties of acetylene gas. (b) How is it manufactured and used for illuminating buildings?

(67) Describe the process of testing gas pipes for leakage.

(68) Mention the most important considerations in locating gas fixtures, and state the objections to swing brackets.

(69) Describe flush fittings and mention the class of work for which they are especially made.

(70) Describe shower, needle, and douche baths, and mention the advantages of shower baths in public institutions.

(71) Describe a simple method of removing odors from a kitchen range.

(72) What are the most important points to be considered in selecting the location of plumbing fixtures?

(73) What points should be considered in selecting rainwater leader traps?

(74) Explain the use of the main disconnecting trap on house-drainage work, and state where this trap should be located.

(75) What should be the size of water-supply pipes to the several plumbing fixtures in a three-story building having a tank in the attic?

(76) (a) What is the candlepower of acetylene gas? (b) How many 5-foot Batswing burners, consuming ordinary coal gas (16 candlepower), will be required to furnish as much light as that from a well designed acetylene burner consuming 5 cubic feet of acetylene in the same time?

Ans. (b) About 15 burners.

(77) Describe (a) the Batswing burner, (b) the Argand burner, (e) a well known burner of the regenerative class.

(78) (a) What should be the primary aim of all schemes of artificial illumination? (b) How can it be best accomplished?

(79) For what purposes are earthen pipes suitable in plumbing work?

(80) Show by sketch how the lead waste pipe of a set of three porcelain tubs should be run. The waste water must discharge into a 3-inch cast-iron pipe stack at the back of the left-hand tub. Use a f 3/4 round-pipe trap, and back-vent it into the stack.

(81) Which is the more safe, a cast-iron waterback or a copper-pipe firebox coil? State your reasons.

(82) What is the cost of 76 feet of 3/4-inch AA lead pipe at 6 cents per pound; 110 feet of 1 1/2-inch D lead pipe at 7 cents per pound; 96 feet of 4-inch 8-pound lead waste pipe at 7 cents per pound; 56 feet of 5/8-inch A A block-tin pipe at 20 cents per pound? Ans. $102.97.

(83) (a) Describe two forms of grease traps, and state the kind of work for which they are particularly adapted. (b) Which is the more efficient? Give reasons.

(84) Briefly describe the process of ventilating house drains and soil pipes when a main drain trap is used.

(85) (a) How can mechanical impurities be removed from water? (b) How can water which has grown stale by standing be made potable and fresh?

(86) Describe the process of manufacturing gasoline gas for use as an illuminant in buildings.

(87) Describe an incandescent gas lamp. Explain how the gas is consumed, and the light produced.

(88) How many 5-foot Batswing burners will be required to properly illumine an auditorium, 65 ft. X 90 ft, and two balconies, each having 1,200 square feet of floor area?

Ans. 206 burners.

(89) What class of a trap would you place under a bath that is very seldom used? Give your reasons.

(90) Describe, and show by sketch, a front outlet washout closet.

(91) Explain the difference between single and double riveted boilers. What class of work are they respectively adapted for?

(92) (a) Distinguish between butt-welded and lap-welded iron pipe, (b) Under what pressures are they tested respectively? (e) Which sizes are butt welded, and which are lap welded?

(93) Clearly explain how a trap can lose its seal by siphon-age, and state how the seal can be maintained intact.

(94) (a) Describe the hydrostatic test as applied to plumbing. State the object of the test, (b) Describe the smoke test and state its object. How can you tell if the drainage system is tight?

(95) What are the most important points to be considered in the selection of a good water filter? Give your reasons.

(96) How many U. S. gallons of gasoline of the best grade are required to furnish 15-candlepower gas to ten 5-foot burners for 100 hours? Ans. 22.5 gal.

(97) (a) Describe atmospheric burners. Explain how the gas is burned, (b) Distinguish between the "solid" flame and the "Bunsen" flame.

(98) What is a candlepower?

(99) (a) State the disadvantages of the common bell trap, (b) Is it adapted for house-draining work?

(100) Draw a vertical section through a siphon-jet water closet. Describe this closet and explain its action.