Water distribution practice exam #2 (D1-D2) questions and answer Which process converts ammonia to nitrite and nitrate? - Answer- Nitrification What is the maximum advisable rate of chlorine gas removal from a 150- pound cylinder? - Answer- 40 pounds per day What is a type of positive displacement water meter? - Answer- Nutating- disk meter What is a power-operated mechanism for opening and closing a valve? - Answer- Actuator What is required if a routine sample test positive for total coliform bacteria? - Answer- Take repeat samples Why is a grid layout better than a tree layout for a water distribution system? - Answer- Less dead-end mains What is the purpose of a reduced pressure principle assembly? - Answer- Prevents back-pressure and back-siphonage In general, at what depths is shoring required for a trench, if you're excavating in soil? - Answer- 5 feet or deeper What occurs after breakpoint chlorination is achieved? - Answer- Free available chlorine residual is directly proportional to the amount of chlorine added What is used to automatically shut-off the flow into a tank when the water level reaches a pre-determined level? - Answer- Altitude valve What would be used to find a chlorine gas leak, which produces white smoke when it reacts with this substance? - Answer- Spray ammonia solution vapor near leak What causes staining of plumbing fixtures? - Answer- Iron & manganese How long should you flush water before you collect a bacteriological sample? - Answer- As long as necessary to flush stagnant water from the service pipe What is the purpose of a surge tank? - Answer- Protect pipelines from sudden high pressure 1 / 2
What is recommended if a chlorine gas cylinder is leaking? - Answer- Rotate the cylinder and turn the leak upwards What is the purpose of primary MCL? - Answer- To protect human health What problem could be used by water with a pH of 5.3? - Answer- Corrosión What is a common way to connect a new pipe to an existing pipe, while the latter is pressurized and in-service? - Answer- Wet tap or hot tap What impact would organics have on chlorine demand? - Answer- Increase chlorine demand What is dichloramine? - Answer- Combined chlorine residual What impact does tuberculation have on the interior of a water main? - Answer- Causes rough interior of the water due to corrosion What is used to neutralize chlorine residuals when collecting a water sample for bacteriological analysis? - Answer- Sodium thiosulfate What are electrodes and ultrasonic signals used for in a tank? - Answer- Monitor water level Which part of the water main should a new service tap be installed? - Answer- 45 degrees from the top of the water main What is the purpose of a vacuumed breaker? - Answer- Prevent back siphonage Which type of valve is commonly used to isolate water mains during repairs to minimize service outages? - Answer- Gate valve Pumping water level - static water level = - Answer- Drawdown What is purple pipe used for? - Answer- Reclaimed water Where is the correct location to install an air release valve - Answer- Top of pipe What must be performed prior to entering a confined space? - Answer- Test for oxygen deficiency/enrichment, combustible gases, and toxic gases What does the C- factor of a pipe represent? - Answer- Roughness of pipe interior Why should you never empty an underground storage tank when the groundwater level is high? - Answer- It may float the tank and cause damage to the facility
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