Here are the answers to practice problem No. 5. 

1. What is wrong with the calculation of the average daily flow?

Answer: I did not consider the drainback each time the pump ran. It is approximately 14 gallons each time so:

64 gallons – drainback of 14 gallons = 50 gallons actually delivered to the system.

Total flow then becomes: 640 cycles x 50 gallons/cycle = 32,000 gallons delivered

Average daily flow becomes: 32,000 gallons ÷ 120 days = 267 gallons/day

2. Would that change what you think about how this system is operating?

Answer: Now the average daily usage is less than the design flow for the system; since it is close to the design flow it probably means that flow is exceeded since this is an average. Therefore, looking at potential extraneous sources of water and flow reduction with the homeowner would be a good idea.