HomeMy WebLinkAboutSanitary Sewer Flow CalculationsWash Tunnel Building ‐ Wash Water Discharge1
Vehicles per Day 400 avg
1000 max
Water Flow Rate 201 gpm
Fresh Water (per vehicle) 16 gal (Remaining to be from WW Reclaim Pit)
Avg. Daily Flow (to sewer) = 6400 gal (Assume WW Reclaim Pit is operational)
Max. Daily Flow (to sewer) = 16000 gal (Assume WW Reclaim Pit is operational)
Peak Flow Rate =201 gpm (If WW Reclaim Pit is out of service)
Detail Bay Building ‐ Wash Water Discharge2
Vehicles per Day 12
Water Flow Rate 4.5 gpm
Wash Duration (per vehicle) 7 minutes
Avg. Daily Flow (to sewer) = 378 gal
Peak Flow Rate = 4.5 gpm
Flow Rate from Bathrooms
Employee Estimate 11 (Entire Facility ‐ Wash Tunnel, Detail Bay, Sales Area)
Avg. Daily Flow Rate 12 gpcd (Per DEQ Circular 4, Sec. 3.1, Table 3.1‐1)
Avg. Daily Flow = 132 gal/day
Peaking Factor 4.41 (Harmon Formula)
Peak Flow Rate = 582.1 gal/day
0.404 gpm
0.0009 cfs
Total Flow to Sanitary Sewer
Contributing Area 2.725 acres
Assumed Infiltration Rate 150 gal/acre/day
Infiltration = 408.75 gal/day
0.284 gpm
Avg. Daily Flow = 7319 gal/day (Assume WW Reclaim Pit is operational)
Peak Flow Rate = 206.188 gpm (If WW Reclaim Pit is out of service)
0.459 cfs
Gallatin Center Car Wash
Sanitary Sewer Flow Calculations
Notes
1. The automated car wash in the wash tunnel building operates almost exclusively on recycled water from the
water reclaim pit. So Although the flow rate into the tunnel during a car wash is 201 gpm, only an average of
16 gallons of fresh water will be used for each vehicle being washed. Therefore, only approximately 16 gallons
of recycled water will be discharged from the reclaim pit to the sanitary sewer system for each vehicle washed.
This estaimate of 16 gal / vehicle and the estimate of 400 vehicles washed per day was used to calculate the
average daily flow anticipated to be discharged to the sanitary sewer main from the wash tunnel. However, if
for some reason the reclaim pit is out of service, then all wash water generated during the car wash (201 gpm)
would be discharged to the sanitary sewer system because no recycled water would be used. Therefore, the
max possible (peak) flow to the sanitary sewer system from the wash tunnel is 201 gpm.
2. The detail bay building is estimated to wash 12 vehicles per day, with an average wash time of 7 minutes /
vehicle at a water flow rate of 4.5 gpm. Since this building is not connected to the reclaim pit, all of the water
used in car washes for this building will be fresh water and all of it will be discharged to the sewer system.
These estimates were used to determine the average daily flow to the sewer system from the detail building.
However, while vehicles are being washed the max possible (peak) flow rate to the sewer system will be 4.5
gpm.