Chilled Water Valve Tags: CHW vs CHWS vs CHWR (Simple Guide)
Chilled water systems are used to cool buildings. The system pushes cold water out to air handlers and coils, then brings warmer water back to be cooled again.
In most buildings, the chilled water piping is one of the busiest systems in the mechanical room. There are often dozens of valves, and many of them look exactly the same. If they are not labeled, techs waste time and can shut off the wrong line.
That is why chilled water valve tags matter.
This guide explains the difference between CHW, CHWS, and CHWR, and how to label valves correctly in the field.
What CHW, CHWS, and CHWR should mean
CHW = Chilled Water (general)
Use CHW as a general label when you are talking about the chilled water system as a whole, or when the job does not require separating supply vs return.
CHW is a good “system-level” label, but it can be too vague in larger buildings.
CHWS = Chilled Water Supply
CHWS is the cold water leaving the chiller and going out to the building loads.
If a coil is not cooling, CHWS is usually the first side you check for temperature and flow.
CHWR = Chilled Water Return
CHWR is the warmer water coming back from the building loads and returning to the chiller.
CHWR helps you confirm that the system is picking up heat and that water is actually moving through the coils.
Why the difference matters in real service work
1) Faster troubleshooting
When an air handler is not cooling, a tech often checks:
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Is CHWS cold at the coil?
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Is CHWR warmer than CHWS?
-
Are the correct isolation valves open?
If valves are tagged CHWS and CHWR, these checks are quick and clear.
2) Preventing wrong-valve shutdowns
CHWS and CHWR lines are often side-by-side. If valves are not labeled, it is easy to shut off the wrong one and cause:
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loss of cooling in the wrong zone
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poor flow through other coils
-
unbalanced systems that take time to stabilize
3) Better communication between crews
With clear tags, people can say:
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“Close CHWS 014 for that coil”
instead of -
“Close the second valve next to the pump behind the strainer.”
Best practice: how to tag chilled water valves
Tag the plant and main distribution first
Start with the most important valves in the system:
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chiller isolation valves (supply and return)
-
pump suction and discharge isolation valves
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main headers leaving the plant
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major branch takeoffs to wings or floors
These are the valves that affect the most equipment.
Tag equipment-level isolation next
After the mains, move to the valves that techs touch during service calls:
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air handler coil isolation valves
-
terminal unit isolation points (if used)
-
control valve stations
-
risers and zone branches
If it is a valve a tech might close during maintenance, it should be tagged.
Numbering systems that work
Option 1: Separate sequences by system
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CHWS 001, CHWS 002, CHWS 003
-
CHWR 001, CHWR 002, CHWR 003
This makes it very clear what side of the system you are on.
Option 2: Number by area
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East wing: CHWS 001–050 and CHWR 001–050
-
West wing: CHWS 051–100 and CHWR 051–100
This is helpful for large buildings where many valves repeat.
The main goal is consistency. Pick one method and use it everywhere.
Where to place tags so they are easy to read
Tags work only if people can see them. Place them:
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at the valve operator, where a person stands to turn the valve
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in a spot that does not get buried behind insulation
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where it will not rub constantly on the pipe or other parts
If a valve is insulated, place the tag where it will still be visible after insulation is installed.
The master list makes tags more valuable
Valve tags are strongest when they match a simple list or drawing.
A basic spreadsheet works fine:
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Tag number (CHWS 012)
-
Location (Mech Room 4, north wall)
-
What it serves (AHU-2 chilled water coil)
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Notes (normally open, locked open, etc.)
This helps new techs and prevents confusion later.
Stock vs custom chilled water valve tags
If you want a fast and standard setup for common system codes like CHW, CHWS, and CHWR, stock tags are the easiest way to start.
Stock Valve Tags: https://printproaz.com/collections/stock-valve-tags
If your building uses special abbreviations, a custom numbering format, or extra text, custom tags are the better fit.
Custom Valve Tags: https://printproaz.com/collections/custom-valve-tags
Final tip
CHWS and CHWR should be clear and consistent across the building. When chilled water valves are labeled correctly, troubleshooting is faster, wrong shutoffs happen less often, and maintenance work is cleaner.
If your goal is simple: tag supply and return separately. That is what keeps techs from guessing in the field.