34 Pa. Code § 3a.28 – Blowoff tanks.

(a) Blowoff piping from a power boiler or a miniature boiler may not discharge directly into a sewer. A blowoff tank will be used if conditions do not provide an adequate and safe open discharge.
(b) ASME Section VIII, Division l governs the construction of metal blowoff tanks.
(c) The cross sectional area of the outlet from blowoff tanks must be twice the area of the inlet. The outlet pipe must be located to drain the blowoff tank to within 8 inches of the bottom of the tank.
(d) A vent pipe comprised of at least four times the area of the inlet pipe must lead to the outer atmosphere.
(e) Vents must lead as directly as possible to the outer air and discharge in a safe location. There may be no valve or other obstructions such as water pockets between the tank and the discharge end of the vent pipe.
(f) Pipe connections between the boiler blowoff valves and the tank must be as direct as possible and conform to the ASME Code.
(g) A manhole or an access opening shall be installed for cleaning the tank.
(h) A blowoff tank that is not vented as required in this section must meet one of the following requirements:
1. (1) Constructed to withstand pressure equal to the pressure allowed on its attached boiler.
2. (2) Equipped with a safety valve or valves of sufficient capacity to prevent the pressure from exceeding the safe working pressure of the tank.