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Plumbing & fire protection abbreviations

Common abbreviations found on plumbing and fire protection drawings. Quick reference for interpreting mechanical plans and specifications.

Categories
Access & Inspection (4)Fixtures & Appliances (9)Piping & Materials (9)Water Systems (7)Valves & Flow Control (9)Drainage (5)Venting (3)Fire Protection (6)Measurements & General (15)

Access & Inspection

AP
Access Panel
CO
Cleanout
FCO
Floor Cleanout
GCO
Ground Clean Out

Fixtures & Appliances

BT
Bath Tub
DF
Drinking Fountain
EWC
Electrical Water Cooler
Alternative term for drinking fountain
MSB
Mop Service Basin
SH / SHWR
Shower
SK
Sink
TLT
Toilet
U
Urinal
WC
Water Closet
Toilet

Piping & Materials

CI
Cast Iron
CLDI
Cement Lined Ductile Iron
CONC
Concrete
CP
Chrome Plated
GALV
Galvanized
GI
Grease Interceptor
ID
Inside Diameter
OD
Outside Diameter
SS
Soil Stack or Stainless Steel

Water Systems

CW
Cold Water
CWR
Cold Water Return
CWS
Cold Water Supply
HW
Hot Water
HWR
Hot Water Return
HWS
Hot Water Supply
TW
Tempered Water

Valves & Flow Control

BWV
Back Water Valve
DCVA
Double Check Valve Assembly
FHV
Fire Hose Valve
FV
Flush Valve
NC
Normally Closed
NO
Normally Open
PIV
Post Indicator Valve
RPBP
Reduced Pressure Backflow Preventer
VB
Vacuum Breaker

Drainage

IW
Indirect Waste
OED
Open End Drain
SD
Sanitary Drain
W
Waste
WS
Waste Stack

Venting

V
Vent
VS
Vent Stack
VTR
Vent Through Roof

Fire Protection

FEC
Fire Extinguisher Cabinet
FP
Fire Protection
FPWH
Freeze Proof Wall Hydrant
FS
Flow Switch
TS
Tamper Switch
WH
Wall Hydrant

Measurements & General

CFH
Cubic Feet per Hour
CFM
Cubic Feet per Minute
DIA
Diameter
EL / ELEV
Elevation
FLR
Floor
FT
Foot or Feet
GPF
Gallons per Flush
GPM
Gallons per Minute
INV
Invert
MECH
Mechanical
PLBG
Plumbing
PSI
Pounds per Square Inch
SA
Shock Absorber
TYP
Typical
VFD
Variable Frequency Drive
Attribution

Abbreviation reference courtesy of Archtoolbox. For the most up-to-date abbreviations and additional resources, visit their website.

Practitioner insight

“Half the plumbing RFIs we see at the shop-drawing stage start with someone misreading an abbreviation, usually because the project's legend was on sheet P-0.0 and the field crew was working off a printed sheet from the middle of the set. Putting a project-specific abbreviation legend on every plumbing sheet is one of the easiest QC wins.”

Conversations with MEP coordinators and plumbing project managers reviewing plumbing shop drawings on healthcare, institutional, and multifamily projects.

Frequently Asked Questions

What is the most common plumbing abbreviation to know on construction drawings?
The most frequently used plumbing abbreviations on construction drawings are CW (cold water), HW (hot water), HWR (hot water return), SAN (sanitary waste), V (vent), ST (storm), G (gas), and FP (fire protection). These appear on every plumbing drawing set. Beyond those, fixture abbreviations (WC for water closet, LAV for lavatory, UR for urinal, FD for floor drain) and valve types (BV for ball valve, GV for gate valve, CV for check valve) are the next tier.
What is the difference between SAN and SS on a plumbing drawing?
SAN (sanitary) and SS (sanitary sewer) both refer to drainage carrying waste from fixtures. SAN is more commonly used inside the building (sanitary waste piping). SS is more commonly used at the site-utility interface (sanitary sewer leaving the building). On a plumbing plan you'll typically see SAN with a 4" / 6" callout serving fixture groups; on a civil utility plan you'll see SS with invert elevations and pipe slope.
What does CWS, CWR, HWS, HWR mean in HVAC vs plumbing drawings?
On HVAC drawings, CWS (chilled water supply) and CWR (chilled water return) are the chilled-water loop serving cooling coils, and HWS (hot water supply) and HWR (hot water return) are the heating-water loop serving heating coils. On plumbing drawings, CW (cold water) and HW (hot water) without the S/R suffix are the domestic water serving fixtures; HWR (hot water return) is the recirculation line. The HVAC vs. plumbing context disambiguates, these abbreviations clash and are a common source of drawing-review confusion.
What are the standard fire protection abbreviations?
FP (fire protection, general), SP (sprinkler), SS (sprinkler supply or sometimes sanitary sewer, context-dependent), STR (standpipe riser), HD (hose), DCDA (double check detector assembly), RPZ (reduced pressure zone backflow), and FDC (fire department connection). NFPA 13 sprinkler density and coverage data appear in the schedule but the piping itself is called out with SP on the plan.
What does ABV / BLW mean on plumbing drawings?
ABV (above) and BLW (below), sometimes written ABV CLG (above ceiling) and BLW FLR (below floor), indicate the vertical location of piping relative to the floor or ceiling. They're essential on small-bore piping that doesn't show up on plan as a routed line but needs vertical reference for installation. Missing ABV/BLW notation on tight ceiling cavities is a common cause of MEP coordination conflicts.
Where can I find a standard list of plumbing abbreviations?
ASPE (American Society of Plumbing Engineers) publishes a standard list of plumbing symbols and abbreviations. IPC (International Plumbing Code) and the National CAD Standard (NCS) both reference it. Most engineering firms maintain their own internal abbreviation legend on the first sheet of the plumbing drawing set (typically P-0.0 or P-001), that legend is the authoritative list for that specific project and should be the first place to look when an unfamiliar abbreviation appears.
MG

Manas Gandhi

Co-founder & CTO, Helonic

Manas is the co-founder and CTO of Helonic, where he leads engineering and AI research for construction drawing analysis. He works directly with structural, MEP, civil, and fire protection engineers to translate the way they review drawings into AI systems that flag the issues that actually matter in the field. Before Helonic, he built machine learning pipelines for technical document understanding and has spent the last several years interviewing licensed design engineers and discipline leads to ground product decisions in real practice rather than industry assumptions.

Areas of focus
  • AI for technical document understanding
  • Cross-discipline coordination workflows
  • Code compliance automation (IBC, NEC, NFPA, IPC, IMC, ASCE)
  • Structural and MEP drawing review systems

Last reviewed by Manas Gandhi · May 2026

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Decode plumbing drawings instantly

Helonic's AI understands plumbing abbreviations and can identify coordination issues, verify fixture counts, and flag discrepancies across your MEP drawing set.