Page 365 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch09_297-332.qxd 8/2/10 9:54 PM Page 325

9.5 Reduced Pressure Principle Backflow Preventer 325
Figure 9.27 Types of Reduced pressure zone backflow
Reduced Pressure Zone preventer ( 4 inch thru 2 inches).
3
Backflow Preventers.
Conversion factors: 1 inch
25.4 mm; 1 psi 6.94 kPa
95 psi
94 psi
100 psi

Supply 60 psi 1 / 4 1 / 4
Out 47 psi
50 psi

1 / 4

(a)

Reduced pressure zone backflow
1
preventer (2 2 inches thru 10 inches).

Reduced pressure zone
1st check valve 2nd check valve

94 psi 93 psi
100 psi

Relief valve (rotated 90
for clarity)

(b)