Here are some guidelines that can help you
select a condensate drain valve. The article outlines a two step
process to selecting a condensate drain valve.
- Choose the best
type of valve for your application.
- Match the operating
conditions with the drain valve's specifications.
To buy or learn more about each drain
valve, browser our selection of Drain Valves. Or use or Search by
Application Chart to find the right drain valve by
your specific system.
Ball Valve Drains - View
If you need to drain an air receiver
or other similar pressure vessel the best choice is a ball valve
drain. Compared to other types of drain valves ball valve drains
are not affected as quickly by dirt, oily sludge, rust, and the
other gunk that comes out of receiver tanks. Motorized ball valve
drains with timers are a little more expensive than direct acting
drains, however the headaches saved probably make the expense
When you have a large amount of pipe scale and other gunk your
best choice is a ball valve style drain valve. Common dirty drain
valve applications include:
Tec-44 Ball Valve
- • Air receivers (tanks)
- • Air dryers
- • Compressor and/or
- • Filters
Standard electronic solenoid drain
valves can be installed on air receivers and in other dirty
applications; however, you should install a strainer with these
drains to allow easy access and protection from pipe scale and
No-loss drain valves eliminate the
compressed air consumed by other types of drains. The return on
investment is often weeks.
A no-loss drain valve collects condensate in a small reservoir and
discharges it when a certain volume has been reached without
consuming any compressed air. So no-loss style drains reduce the
amount of compressed air consumed. For example a DEHYDRA52 collects
52 ounces of condensate before it cycles discharging the condensate
In a large well maintained system, no-loss drains can save
thousands of dollars a year paying for themselves normally in less
then 3 months. So, no-loss drains are a good choice for systems
over 1000 SCFM who have done a
compressed air audit and have an active leak monitoring program.
Another reason you may want a no-loss drain is because some are
pneumatically operated like the Smart Guard POD and ROBODRAIN. So
if you don't have power available, you can use these drains without
running new electric.
Gravity type condensate oil/water separators that are fed from
no-loss drains work better because the condensate is not constantly
emulsified by the blow down you get from electronic drain valves.
Chemical adsorption oil/water separators like the PURO models are
not effected by blow down from drains because they don't use
gravity separation tanks.
A niche no-loss drain application is in conjunction with
centrifugal air compressors. On centrifugal air compressors two
no-loss drain valves are recommended at each intercooler location.
This is to protect the expensive compressors from potential damage
from a drain trap failure. At the same time, an electronic drain
may fire to often or not enough either trapping moisture or wasting
Drains - View Models
Electronic timer or direct acting
drain valves are less expensive than no-loss and ball valve drains.
Most electronic drain valves let you set the drain to come on once
every 10 seconds to 45 minutes and remain open for 0.10 to 10
Electronic Drain Valve
The condensate is blown out of the
drip leg or filter housing with some compressed air. Electronic
drain valves are normally used on drip legs, separators, filter
housings, and nearly anywhere else in the compressed air system
where condensate collects.
If the condensate contains a large amount of dirt, a strainer
should be added to the electronic drain valve. The strainer will
stop the dirt from clogging the drain valve orifice. The size of
the drain's orifice affects how much compressed air will be
expelled with the condensate each time the drain fires. Operating
pressure and discharge time are also factors.
Diaphragm style electronic drain
valves have larger orifices than most direct acting drain valves.
Because of the larger orifice it is generally accepted diaphragm
drain valves are less likely to foul than direct acting valves.
Diaphragm drain valves do use more compressed air than their direct
acting cousins. In the end, the choice between direct acting and
diaphragm drain valves is really a coin toss. Both are good
electronic drain valves and can be used in the same applications. A
strainer should be used with a diaphragm valve in dirty
Of course there are some basic
operating conditions to consider when selecting any drain valve.
- • Amount of condensate being
- • Maximum temperature
- • Maximum pressure
- • Valve body material
- • Discharge and interval
- • NPT Connection
- • Electric
- • Orifice size
- • Type of valve (discussed at
From the lengthy discussion above
you've probably concluded correctly the most important factor is
the type of valve. Once you have decided between...
- • No-loss
- • Ball valve
- • Direct acting
- • Diaphragm
The other specifications help you
choose the best fit for your situation. Most drain valves can
handle nearly any condensate load, but best practice in large air
systems (1000 SCFM larger) is to use ball valve drains and large
no-loss drains in applications closest to the air compressor
including the air receiver and aftercooler separator. The next
thing to consider is the pressure you are operating at and the
air's temperature. Drain valves for high temperatures and pressures
are readily available. However, most are rated around 200F and 250
PSI because most compressed air systems operate at less than these
The valve body material is normally brass or bronze or stainless.
Stainless steel valves are commonly used in corrosive environments,
sanitary applications, and in systems piped in stainless. If
chemical compatibility is a concern with your process be sure to
check the valve body material. Some drains like the Optimum series
are NEMA4. Explosion-proof NEMA7 drain valves are a custom product.
The closest standard product to NEMA7 is a pneumatically operated
no-loss drain valve.
Drain valves come in nearly all electric formats making it easy to
match a drain with what you have available at the installation
point. Most 120 VAC drains come with a six foot cord and plug ready
for a standard outlet. Drain valves are available in...
- • 120 VAC
- • 220 VAC
- • 24 VAC
- • 24 VDC
- • and more
So, you can generally select a drain
by the electric you have available at your installation point.
Additionally pneumatically operated drain valves like the no-loss
ROBODRAIN don't require any electric.
The connection size can be selected to match what your installing
the drain valve on. For example a 1/4'' NPT connection at the
bottom of a filter bowl would take a 1/4 NPT drain valve. Drain
valves have female NPT connections. Don't always blindly match the
drain to the connection size also consider the application. For
example, a 1/4'' NPT drain valve is not a good choice for a 1500
gallon air receiver.
Hopefully this short article helped you select a drain
valve for your compressed air system. eCompressedair offers a
full line of compressed air drain valves online. For help offline
call us toll-free 866-650-1937.