3. Back-flow prevention.

Question 0

3. Many types of hospital fixtures are equipped with hose attachments for spray or with connection to submerged inlet to fixtures. What type of protective device should be used with this type of equipment?

Answer 0

A vacuum breaker should be installed between the water supply outlet and the hose attachment or submerged supply in order to prevent any possibility of back-siphonage.

Question 1

1. What conditions can cause a vacuum in a supply line?

Answer 1

The water supply fails, a main breaks, the supply line is shut off and drained, an unusually heavy draw is caused by a fire in the vicinity, or there is a heavy draw at a low point in the system.

Question 2

4. Sketch of reduced pressure principle back-flow preventer?

Answer 2

See figure 147.

Question 3

5. Sketch double check-valve assemblies.

Answer 3

See figure 148.

Question 4

6. Typical installation of an RPZ with water meter located in cellar?

Answer 4

See figure 39.

Question 5

7. Typical installation of an RPZ and meter in a building without a basement?

Answer 5

See figure 38.

Question 6

8. Typical installation of a an RPS and water meter in a basement?

Answer 6

See figure 37.

Question 7

9. The degree of hazard back flow preventing devices.
10. High hazard.
11. High or low hazard.
12. Low hazard.

Answer 7

1. High hazard:
   
   1. Antisiphon-type fill valves for gravity water closet flush tanks.
2. High or low hazard.
   
   1. Air gap.
3. Air gap fittings for use with plumbing fixtures, appliances and appurtenances.
4. Barometer loop.
5. Reduced pressure principle back-flow preventer and reduced pressure principle fire protection back-flow preventer.
6. Reduced pressure detector fire protection back-flow prevention assemblies.
7. Pipe-applied atmospheric type vacuum breaker.
8. Pressure vacuum breaker assembly.
9. House-connection vacuum breaker.
10. Vacuum breaker wall hydrants, frost-resistant, automatic draining type.
11. Lavatory faucet back-flow preventer.
12. Hose connection back-flow preventer.
13. Spill-proof vacuum breaker.
14. Low hazard.
    
    1. Double check back-flow prevention assembly and double check fire protection back-flow prevention assembly.
    2. Double check detector fire protection back-flow prevention assemblies.
    3. Dual-check-valve-type back-flow preventer.
    4. Back-flow preventer with intermediate atmospheric-type vents.
    5. Back-flow preventer for carbonate beverage machines.

Question 8

10. Back flow prevention of sterilizer or flushing rim floor drain.

Answer 8

Water supply must be through air gaps and direct water connections to potable water supply system must be done by use of reduced pressure principle back pressure back flow preventer installed between water supply and equipment.

Question 9

11. Back-flow prevention of bedpan washer (no flushometer)?

Answer 9

Must be equipped with vacuum breaker and check valve - check valve to be located between fixture and vacuum breaker.

Question 10

12. Back flow prevention of laboratory outlet serrated tip?

Answer 10

Shall be provided with vacuum breaker.

Question 11

13. Back-flow prevention of automatic cloths washer?

Answer 11

By means of adequate air gap or a vacuum breaker.