Multi-stage, centrifugal, air and gas blowers & exhausters are generally designed to take in clean, filtered air, or gas, and discharge it to "the system".  The key words here are "clean & filtered".  There are installations where the blowers do operate for years just as they were designed to, and therefore, problem free!  But there are a whole lot more installations where the blowers are subjected to ingesting many types of foreign materials, especially moisture.  And unless the blower is ordered with "drains", the lifespan can be shortened dramatically.

Wastewater treatment plants generally operate 24/7 with a common header so they don't get much water in their systems. But accidents happen: floods, backups, etc..., especially in the "water" business. During extended periods of downtime, when the humid air in the many lengths of piping cools, the resulting moisture condenses and collects in the lowest point of the system, which is usually the blower.  Landfill gas flares ingest the heavily moisture laden, saturated gas, so they must have the drains.   

Obviously, it is best to prevent water from getting into the blowers. But if your blower has not been drilled for section drains, there is no easy way to get the water out!  The drains cannot be added in the field, but they can be added during a blower "recondition". More than once, frozen water inside a blower has resulted in a catastrophic blower failure!

During the manufacture of the cast iron sections, they may, or may not, be drilled & tapped with section drains.  And sometimes, but not always, the individual sections have drilled 'internal drains' connecting each other. This way, if a drain hole plugged up, the water could drain to the next section and out the drain.

The drain holes are tapped with a standard pipe thread to allow the customer to "pipe" the drains, often to a common header with a ball valve.  Individual valves are also common, as is using stainless steel, or PVC for the piping.  Some customers have used petcock valves with success, especially in very hard to reach installations. Any type of valve is easier than leaving the pipe plugs.

There is no "best way" to install drain piping.  Each blower Model, and the customers' situation, determine the type of piping to install.  From a maintenance point of view, all centrifugal blowers should have piped drains with a ball valve! It will no doubt extend the life of your blower and save you time and money in maintenance! 

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