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International Plumbing Code (IPC Table E103.3)37 Verified Home & Distance Scenarios

Water Supply Pipe Sizing & WSFU Matrix

Deterministic hydraulic directory for licensed plumbers, general contractors, and home builders. Select your bathroom count and setback distance below to access comprehensive factsheets covering PEX vs Copper main sizes, peak GPM demand, friction loss, and maximum 8.0 fps water hammer velocity limits.

Zero-Rounding Bias
Modified Hunter's Curve
8.0 fps Water Hammer Cap
Custom WSFU Calculator

Featured Sizing & Material Decision Guides

PEX vs Copper
3 4 vs 1 inch water line 2 bath
For a 2-bathroom home (14.5 GPM peak), 3/4" Copper handles 100 ft easily (6.8 fps), but 3/4" PEX reaches 8.5 fps (exceeding IPC limits). Upgrading PEX to 1" eliminates water hammer and future-proofs the home for irrigation.
22 WSFU·14.5 GPM·1" PEX
3 4 vs 1 inch water line 3 bath
A 3-bathroom home exerts 19.0 GPM peak demand. A 3/4" water main is severely undersized under IPC standards (causing 11.2 fps velocity and high friction drop). A 1-inch main is mandatory for proper multi-fixture shower performance.
31 WSFU·19 GPM·1" PEX
pex vs copper pipe size 2 bath
Due to thicker PEX SDR-9 walls, 3/4" PEX has an inner diameter of only 0.671" vs 0.785" for 3/4" Type L Copper. Plumbers frequently use 1" PEX for the main trunk line, transitioning to 3/4" and 1/2" branch manifolds.
22 WSFU·14.5 GPM·1" PEX
pex vs copper pipe size 3 bath
For 3 bathrooms (31 WSFU), 1" PEX and 1" Type L Copper provide outstanding volume. Copper offers slightly lower friction drop (3.8 PSI vs 4.8 PSI for PEX over 100 ft), while PEX allows joint-free homeruns from a central manifold.
31 WSFU·19 GPM·1" PEX
pex vs copper pipe size 4 bath
At 24.5 GPM over 150 ft, 1" Copper maintains 9.5 fps (borderline), while 1-1/4" PEX provides 9.1 GPM per square inch (comfortable 6.2 fps). 1-1/4" PEX or 1-1/4" Copper is strongly recommended to prevent shower pressure drops.
42 WSFU·24.5 GPM·1-1/4" PEX

Browse Pipe Sizing by Bathroom Count

IPC Table E103.3 Verified
1B

1 Bathroom Home (Compact / ADU)

14 WSFU Aggregated Load · ~9.5 GPM Peak Demand
PEX Main: 3/4" PEX·Copper Main: 3/4" Type L Copper
50 ft Run
PEX: 3/4" PEX
Copper: 3/4" Type L Copper
Loss: -22.1 PSI8.6 fps
100 ft Run
PEX: 3/4" PEX
Copper: 3/4" Type L Copper
Loss: -44.3 PSI8.6 fps
150 ft Run
PEX: 1" PEX
Copper: 3/4" Type L Copper
Loss: -19.6 PSI5.2 fps
200 ft Run
PEX: 1" PEX
Copper: 3/4" Type L Copper
Loss: -26.2 PSI5.2 fps
1.5B

1.5 Bathroom Home (Powder Room)

17 WSFU Aggregated Load · ~11.5 GPM Peak Demand
PEX Main: 1" PEX·Copper Main: 3/4" Type L Copper
50 ft Run
PEX: 1" PEX
Copper: 3/4" Type L Copper
Loss: -9.3 PSI6.3 fps
100 ft Run
PEX: 1" PEX
Copper: 3/4" Type L Copper
Loss: -18.7 PSI6.3 fps
150 ft Run
PEX: 1" PEX
Copper: 3/4" Type L Copper
Loss: -28 PSI6.3 fps
200 ft Run
PEX: 1" PEX
Copper: 3/4" Type L Copper
Loss: -37.3 PSI6.3 fps
2B

2 Bathroom House (Standard Residential)

22 WSFU Aggregated Load · ~14.5 GPM Peak Demand
PEX Main: 1" PEX·Copper Main: 1" Type L Copper
50 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -14.3 PSI8 fps
100 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -28.7 PSI8 fps
150 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -43 PSI8 fps
200 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -57.3 PSI8 fps
2.5B

2.5 Bathroom House (Suburban Two-Story)

26 WSFU Aggregated Load · ~16.5 GPM Peak Demand
PEX Main: 1" PEX·Copper Main: 1" Type L Copper
50 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -18.2 PSI9.1 fps
100 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -36.4 PSI9.1 fps
150 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -20.5 PSI6.1 fps
200 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -27.4 PSI6.1 fps
3B

3 Bathroom House (Large Family Residence)

31 WSFU Aggregated Load · ~19 GPM Peak Demand
PEX Main: 1" PEX·Copper Main: 1" Type L Copper
50 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -23.6 PSI10.4 fps
100 ft Run
PEX: 1" PEX
Copper: 1" Type L Copper
Loss: -47.3 PSI10.4 fps
150 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -26.7 PSI7 fps
200 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -35.5 PSI7 fps
3.5B

3.5 Bathroom House (Executive Home)

35 WSFU Aggregated Load · ~21 GPM Peak Demand
PEX Main: 1-1/4" PEX·Copper Main: 1" Type L Copper
50 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -10.7 PSI7.7 fps
100 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -21.4 PSI7.7 fps
150 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -32.1 PSI7.7 fps
200 ft Run
PEX: 1-1/4" PEX
Copper: 1" Type L Copper
Loss: -42.8 PSI7.7 fps
4B

4 Bathroom Estate / Multi-Generational

42 WSFU Aggregated Load · ~24.5 GPM Peak Demand
PEX Main: 1-1/4" PEX·Copper Main: 1-1/4" Type L Copper
50 ft Run
PEX: 1-1/4" PEX
Copper: 1-1/4" Type L Copper
Loss: -14.2 PSI9 fps
100 ft Run
PEX: 1-1/4" PEX
Copper: 1-1/4" Type L Copper
Loss: -28.5 PSI9 fps
150 ft Run
PEX: 1-1/4" PEX
Copper: 1-1/4" Type L Copper
Loss: -42.7 PSI9 fps
200 ft Run
PEX: 1-1/4" PEX
Copper: 1-1/4" Type L Copper
Loss: -56.9 PSI9 fps
5B

5 Bathroom Luxury Residence

52 WSFU Aggregated Load · ~29.5 GPM Peak Demand
PEX Main: 1-1/2" PEX·Copper Main: 1-1/4" Type L Copper
50 ft Run
PEX: 1-1/2" PEX
Copper: 1-1/4" Type L Copper
Loss: -9 PSI7.8 fps
100 ft Run
PEX: 1-1/2" PEX
Copper: 1-1/4" Type L Copper
Loss: -17.9 PSI7.8 fps
150 ft Run
PEX: 1-1/2" PEX
Copper: 1-1/4" Type L Copper
Loss: -26.9 PSI7.8 fps
200 ft Run
PEX: 1-1/2" PEX
Copper: 1-1/4" Type L Copper
Loss: -35.8 PSI7.8 fps