Drain Valve

Drain valve, abbreviated as DV, is a type of valve used to drain fluids or gases from a system or container such as lines, valves, vessels and tanks.  They can be part of a valve, used with a bleed ring or just flanged to equipment.  It is designed to provide a convenient means for removing liquids or gases that may accumulate in a particular location.  Drain valves are commonly used in various applications, including plumbing systems, industrial equipment, and automotive systems.

examples of drain valves and their applications

• Plumbing Systems  -  In residential and commercial plumbing, drain valves are often installed at the lowest points in plumbing systems to allow for the removal of water or other liquids.  This is common in water heaters, air compressors, and other systems where the accumulation of water or condensate needs to be periodically drained.
• Automotive Radiators  -  Radiators in automobiles often have drain valves at the bottom to facilitate the draining of coolant for maintenance or repairs.
• Compressed Air Systems  -  Air compressors and compressed air systems may have drain valves to remove condensate that can accumulate in the compressed air.
• Industrial Tanks and Vessels  -  Large industrial tanks and vessels may be equipped with drain valves to empty or drain the contents for maintenance, cleaning, or product changes.
• HVAC Systems  -  Air conditioning and heating systems may have drain valves to remove condensate that forms during the cooling or heating process.

Drain valves come in various designs, including ball valves, gate valves, and butterfly valves, depending on the specific application and requirements.  The choice of valve type depends on factors such as the type of fluid or gas being drained, the size of the system, and the desired flow control characteristics.  The primary function of a drain valve is to provide a controlled and efficient means for emptying or draining a system without the need for disassembly.

Drain Valve Considerations

Drain valves are generally installed on the bottom of the pipe, 90-degrees off of horizontal.  However, in services that are sandy or where there is particulate in the system, consider installing the valve 60-degrees off of horizontal.  This may help mitigate the effects of particulate plugging.  

Sizing of the drain valve should take the following into account  -

• How large does the valve need to be to effectively drain the line?  The smaller the valve, the lower the flow rate through the valve and longer it will take to drain. For example, using a 1/4" valve on a line that is hundreds of feet long, is likely a poor decision. 
• Is the process hazardous and does it require a vacuum truck connection? If the process cannot be discharged directly on to the ground, there should be provisions installed to capture the fluid into a receptacle. 
• Is a vent valve needed? A vent valve upstream of the drain valve will allow for faster discharge through the drain valve.
• Is the process sandy or does it have particulate in the process?  Often times, if operations personnel open the drain and it is plugged, they will try to knock the plug out with a piece of welding rod.  Consider using a larger drain valve and shorter nipple to assist the operator.  When it makes sense, consider the use of a filter upstream of the drain valve to remove the particulate.