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Quick answer: In Charlotte Pipe’s Schedule 40 chart, 10 gpm through 100 feet of 1″ PVC loses about 2.64 psi, while 3/4″ loses 8.76 psi and 1-1/4″ loses 0.68 psi. Charlotte says flow velocity should not exceed 5 feet per second, which 10 gpm already breaks in 3/4″ (6.32 ft/s) but not in 1″ (3.86 ft/s). For fittings, add their “equivalent feet” to the pipe length: a 1″ 90° elbow counts as 2.5 feet of pipe.
Numbers here come from Charlotte Pipe’s Plastics Technical and Installation Manual (pages 35–37), read October 9, 2026. The friction loss chart on page 37 is an image in the PDF, so we read it from the rendered page (saved with this draft). It is for Schedule 40 thermoplastic pipe, per 100 feet. This page has no buy buttons.
Friction loss at household flows (Schedule 40)
| Pipe size | 5 gpm | 10 gpm | 20 gpm |
|---|---|---|---|
| 1/2″ | 5.64 ft/s, 9.92 psi* | 11.28 ft/s, 35.81 psi* | Off chart |
| 3/4″ | 3.16 ft/s, 2.43 psi | 6.32 ft/s, 8.76 psi* | 12.63 ft/s, 31.63 psi* |
| 1″ | 1.93 ft/s, 0.73 psi | 3.86 ft/s, 2.64 psi | 7.72 ft/s, 9.52 psi* |
| 1-1/4″ | 1.10 ft/s, 0.19 psi | 2.21 ft/s, 0.68 psi | 4.42 ft/s, 2.45 psi |
| 1-1/2″ | 0.81 ft/s, 0.09 psi | 1.62 ft/s, 0.32 psi | 3.23 ft/s, 1.15 psi |
| 2″ | 0.49 ft/s, 0.03 psi | 0.98 ft/s, 0.09 psi | 1.95 ft/s, 0.34 psi |
* Over Charlotte’s 5 ft/s limit. Charlotte’s chart notice says velocities over 5 feet per second may result in system failure and property damage.
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Highest chart flow under 5 ft/s
Reading down Charlotte’s chart, the last listed flow that stays at or under 5 ft/s in each Schedule 40 size is:
- 1/2″: 2 gpm (2.26 ft/s); 5 gpm is already 5.64 ft/s.
- 3/4″: 7 gpm (4.43 ft/s).
- 1″: 10 gpm (3.86 ft/s); 15 gpm is 5.79 ft/s.
- 1-1/4″: 20 gpm (4.42 ft/s).
- 1-1/2″: 30 gpm (4.85 ft/s).
- 2″: 50 gpm (4.88 ft/s).
The chart jumps in steps (for example 7, 10, 15 gpm), so the real 5 ft/s point sits between the listed rows.
Fittings: equivalent feet of pipe
Charlotte treats the loss through a fitting as equal to a length of straight pipe of the same size. Add up the equivalent feet for every fitting, then add that to the pipe length.
| Fitting | 1/2″ | 3/4″ | 1″ | 1-1/4″ | 1-1/2″ | 2″ |
|---|---|---|---|---|---|---|
| Tee (run) | 1.0 | 1.4 | 1.7 | 2.3 | 2.7 | 4.3 |
| Tee (branch) | 4.0 | 5.0 | 6.0 | 7.3 | 8.4 | 12.0 |
| 90° elbow | 1.5 | 2.0 | 2.5 | 3.8 | 4.0 | 5.7 |
| 45° elbow | 0.80 | 1.1 | 1.4 | 1.8 | 2.1 | 2.6 |
| Male/female adapter | 1.0 | 1.5 | 2.0 | 2.75 | 3.5 | 4.5 |
Charlotte’s table continues to 12″; we show the sizes used in homes.
Worked example
A 60-foot run of 1″ Schedule 40 PVC with four 90° elbows and one tee branch, carrying 10 gpm:
- Fittings: 4 × 2.5 ft + 6.0 ft = 16 equivalent feet.
- Total: 60 + 16 = 76 feet.
- Loss: 2.64 psi per 100 ft × 0.76 = about 2.0 psi. Velocity 3.86 ft/s, under Charlotte’s 5 ft/s limit.
The same run in 3/4″ would lose roughly 8.76 × (60 + 4 × 2.0 + 5.0) / 100, about 6.4 psi, at 6.32 ft/s, which is over the limit. (Our arithmetic from Charlotte’s tables; elevation change is not included.)
Drain lines are different
Gravity drains are sized with Manning’s equation, not Hazen-Williams. Charlotte says lab tests put the Manning “n” value for ABS and PVC pipe at .008 to .012, and that 0.009 is generally accepted for designing gravity sewer systems. It notes the widely recommended flow velocity for self-cleaning sanitary sewer lines is 2.0 feet per second or more.
Where the chart comes from
Charlotte says friction loss through CPVC and PVC pipe is normally found with the Hazen-Williams equation, using a roughness constant C = 150 for CPVC and PVC pipe. Its chart gives friction head in feet and friction loss in psi, per 100 feet of pipe.
FAQ
How much pressure do I lose in 100 feet of 3/4 inch PVC?
In Charlotte’s Schedule 40 chart, about 2.43 psi at 5 gpm and 8.76 psi at 10 gpm per 100 feet. At 10 gpm the velocity is 6.32 ft/s, over Charlotte’s 5 ft/s limit.
What is the maximum velocity in PVC pipe?
Charlotte’s friction loss chart says flow velocity should not exceed 5 feet per second in Schedule 40 thermoplastic pipe.
How many feet of pipe is a PVC elbow?
Charlotte lists a 90° elbow as 1.5 ft at 1/2″, 2.0 ft at 3/4″, 2.5 ft at 1″ and 4.0 ft at 1-1/2″ of equivalent straight pipe.
What C factor is used for PVC pipe?
Charlotte uses C = 150 for CPVC and PVC pipe in the Hazen-Williams equation.
Related guides
- How to fix low water pressure
- Best water pressure gauge
- Schedule 40 vs 80 PVC
- How to install a PVC union
Sources
- TM-PL (PDF) (charlottepipe.com), read 2026-10-09