Schools and Gymnasiums

Special Design Considerations

• When sizing the hot water needs for a school cafeteria it should be noted that the hot water usage is generally 30 percent less per student than the per person average used in restaurants.
  
• In schools where there are more than one lunch period, there is a possibility that the peak demands of the kitchen may occur simultaneously with the peak demand of a shower period and should be considered when sizing the system.
  
• When considering the amount of usage for showers, wash basins and wash fountains, the average clean-up period is generally 10 minutes after each class.
  
• In co-educational schools, the water usage for the boys and girls locker rooms should be considered simultaneously.
  
• When the gymnasium is used for sporting events, sufficient hot water should be available for both teams and this usage should be considered a dump load. When sizing for a dump load such as this, ensure there is adequate storage available.
  
• Since most maintenance occurs during the evening, the hot water usage required for cleanup is generally small and may not be considered in the sizing of the system.

General "Rules of Thumb" For Sizing

	Max. Hour	Max. Day	Avg. Day
Elementary School Jr. and Sr. High School	0.6 gal/student 1.0 gal/student	1.5 gal/student 3.6 gal/student	0.6 gal/student 1.8 gal/student

Hot Water Demand per Fixture Detail Sizing - Gymnasiums

Fixture	Gallons of water per hour per fixture (calculated at a final temperature of 140ºF)
Basins, public lavatory	8
Bathtubs	30
Foot basins	12
Showers	225

Hot Water Demand per Fixture Detail Sizing - Schools

Fixture	Gallons of water per hour per fixture (calculated at a final temperature of 140ºF)
Basins, public lavatory	15
Dishwashers	20-100
Kitchen sink	20
Pantry sink	10
Showers	225
Service sink	20
Circular wash sink	30

Hot Water Demand per Fixture Detail Sizing - Kitchens

Fixture	Gallons of water per hour per fixture (calculated at a final temperature of 140ºF)
Vegetable sink	45
Single pot sink	30
Double pot sink	60
Triple pot sink	90
Pre-scrapper (oven type)	180
Pre-flush (hand-operated)	45
Pre-flush (closed type)	240
Recirculating Pre-flush	40
Bar sink	30
Basin, lavatory	5

National Sanitation Foundation NSF Final Rinse Water Requirements for Dishwashing Machines

Type and sink of dishwasher	Flow rate gpm	Hot Water requirements at 180ºF to 195ºF maximum
		Heaters without internal storage gph	Heater with internal storage gph
Door type:
16 X16	6.94	416	69
18 X18	8.67	520	87
20 X 20	10.4	624	104
Undercounter type	5	300	70
Conveyor type:
Single tank	6.94	416	416
Multiple tank (dishes flat)	5.78	347	347
Multiple tank (dishes inclined)	4.62	277	277
Silver washers	7	420	45
Utensil washers	8	480	75
Make-up water requirement	2.31	139	139

Method of Sizing

1. Determine the number of fixtures required for the application and calculate the total hot water demand for those fixture.

Number of Fixtures x Gallons of Water per Hour per Fixture = Possible Maximum Demand

2. Determine the Probable Hot Water Demand for the application.

Probable Hot Water Demand = Possible Maximum Demand x Demand Factor

Demand Factors: Schools = 0.40

Gymnasiums = 0.40

Kitchens = 1.00

3. Compare the Probable Hot Water Demand with the 1st Hour Performance Ratings of the Phase III Indirect Water Heater or with the Heat Master Direct Fired Water Heaters.

To convert 180ºF Hot water Demand to 140ºF Hot Water Rating:

180ºF probable hot water demand x 1.50 = 140ºF 1st. hour rating

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