SECOND QUARTER 2026  33
NO. 789
B U L L E T I N
Stop Wasting Steam by Fixing Leaky Valves
Your boiler’s humble blow-down valves may be costing you 
big money. When these valves leak, superheated boiler water, 
which you’ve already burned a lot of expensive fuel to generate, 
flashes into steam and vents to the atmosphere. About the only 
time anyone pays attention to these rugged valves is when they 
can’t be opened or shut properly. It’s a mistake to think that if 
they just open or close, all is well; this is a very costly misconcep­
tion. The very nature of what these valves are exposed to during 
their operation: debris, grit, and sandy detritus shoot across 
the valve disk and seats at velocities exceeding 60 mph, which 
is roughly equivalent to being sandblasted. It’s not surprising 
that, after years of use, they lose their ability to seal properly and 
slowly begin to leak. 
Finding Faulty Blow-Down Valves
Fortunately, it’s a simple process to determine the condition 
of these valves by performing simple temperature measurements 
with a laser thermometer. The following test procedure will pro­
vide a reasonably accurate predictor of valve condition. Place a 
large black iron pipe fitting, like a one-inch tee or elbow, on an 
area of the boiler room floor that stays dry and isn’t near direct 
heating from the boiler’s burners, preferably near the blow-down 
valves. We will use this fitting to measure the ambient tempera­
ture of the boiler room and compare it to the temperature mea­
sured near the outlet of the blow-down valve. 
First, measure the area’s temperature about two feet down­
stream of the blow-down valve under test. Next, measure the 
temperature of the one-inch fitting on the floor of the boiler 
room. There should be a temperature difference of less than 
30°F between the two points. If there’s more, it’s likely an indi­
cation that the blow-down valve is leaking. 
What To Do About A Leaky Blow-Down Valve
Some “Y” type globe blow-down valves have replaceable disks 
and seats. My experience has been that while it’s relatively easy 
to replace the disks, replacing the seats in this type of valve is far 
more challenging. Limited damage to the seat may sometimes 
be overcome by using a new Teflon disk. Replacing the disk is 
worth trying, since this type of valve can be expensive to replace. 
To my knowledge, if the blow-down valve is a ball type, it is 
non-repairable. Hopefully the pipefitter who installed the boiler 
located a union or two, making valve replacement easier. Peruse 
the paragraphs below for the proper technique for using the laser 
thermometer. 
By Bruce Grossman, EZ Timers Manufacturing
Note: All in-print DLI bulletins, including this one, are available on DLI’s Drycleaning Encyclopedia accessible in the Members Only section of 
DLIonline.org. This resource is available to Standard, Gold, Premier, and International Members.
Place a black tee or elbow on the boiler room floor near the 
boiler and leave it there for at least two hours. Measure the 
temperature of the pipe right after the valve under test. If this 
reading is more than 30 degrees F. higher than the temperature 
of the tee on the boiler room floor, the valve is likely leaking.

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