606.5 Water Pressure Booster Systems
A gravity or suction water supply tank shall be provided with an overflow with a diameter not less than that shown in Table 606.5.4. The overflow outlet shall discharge at a point not less than 6 inches (152 mm) above the roof or roof drain; floor or floor drain; or over an open water-supplied fixture. The overflow outlet shall be covered with a corrosion-resistant screen of not less than 16 by 20 mesh per inch (630 by 787 mesh per m) and by 1/4-inch (6.4 mm) hardware cloth or shall terminate in a horizontal angle seat check valve. Drainage from overflow pipes shall be directed so as not to freeze on roof walks.
SIZES FOR OVERFLOW PIPES FOR WATER SUPPLY TANKS
| MAXIMUM CAPACITY OF WATER SUPPLY LINE TO TANK (gpm) | DIAMETER OF OVERFLOW PIPE (inches) |
| 0 — 50 | 2 |
| 50 — 150 | 21/2 |
| 150 — 200 | 3 |
| 200 — 400 | 4 |
| 400 — 700 | 5 |
| 700 — 1,000 | 6 |
| Over 1,000 | 8 |
For SI: 1 inch = 25.4 mm, 1 gallon per minute = 3.785 L/m.
A drain pipe with a valve shall be provided at the lowest point of each tank to permit emptying of the tank. The tank drain pipe shall discharge as required for overflow pipes and shall not be smaller in size than specified in Table 606.5.7.
Water pressure tanks shall be provided with a vacuum relief valve at the top of the tank that will operate up to a maximum water pressure of 200 psi (1380 kPa) and up to a maximum temperature of 200°F (93°C). The size of such vacuum relief valve shall be not less than 1/2 inch (12.7 mm).
Exception: This section shall not apply to pressurized captive air diaphragm/bladder tanks.