Calculator Inputs
Use the responsive form below. Large screens show three columns, medium screens two, and mobile one.
Formula Used
This calculator computes total head and converts it to pressure:
- Total head: Htotal = Hstatic + Hmajor + Hminor + Hreq
- Pressure from head: P = ρ g Htotal
- Hydraulic power: Phyd = ρ g Q Htotal
Major loss models
- Hazen-Williams: hf = 10.67 L Q1.852 / (C1.852 D4.871)
- Darcy-Weisbach: hf = f (L/D) (v² / 2g) with Swamee–Jain friction factor.
- Minor losses: hm = K (v² / 2g) using summed K values.
How to Use This Calculator
- Choose the head loss method for your fluid and pipe type.
- Enter flow rate, pipe diameter, and straight length.
- Add static elevation head from inlet to outlet.
- Include required endpoint pressure if a tool needs it.
- Enter fittings and valve counts to estimate minor losses.
- Set fluid specific gravity and pump efficiency for power estimate.
- Press calculate to view results and download CSV or PDF.
Example Data Table
| Scenario | Flow | Diameter | Length | Static Head | Fittings | Method | Typical Output |
|---|---|---|---|---|---|---|---|
| Site dewatering line | 20 m³/h | 50 mm | 60 m | 12 m | 4×90°, 2×45°, 1 gate | Hazen-Williams (C=130) | ~2–4 bar (depends on layout) |
| Water transfer to tank | 100 gpm | 2 in | 150 ft | 20 ft | 6×90°, 1 check | Darcy-Weisbach (ν=1 cSt) | ~20–40 psi (depends on roughness) |
| Tool supply with required nozzle pressure | 10 L/s | 75 mm | 90 m | 5 m | 3×90°, 2 tees | Hazen-Williams (C=150) | Add required endpoint pressure head |
Tip: For slurry or non-water fluids, prefer Darcy-Weisbach and adjust viscosity and specific gravity.
Professional Guide to Pump Pressure Planning
1) Jobsite pump pressure in real terms
Temporary pumping supports dewatering, washdown, curing, dust control, and water transfer. The goal is to deliver required flow at the endpoint without starving tools or over-stressing hoses. Calculating pressure early reduces rework, prevents low-flow complaints, and supports safer site operations.
2) Total head is the design budget
Total head combines elevation (static head), friction in straight pipe (major loss), fittings and valves (minor loss), and any minimum pressure needed at the discharge device. Treat these as one budget and you will avoid underestimating systems with long runs, many bends, or strict endpoint needs.
3) Flow rate drives losses nonlinearly
Losses rise quickly as flow increases because velocity increases. With Darcy-Weisbach, major and minor losses scale with velocity squared, so higher demand can multiply losses. Hazen-Williams also scales strongly with flow. Size for peak flow, not average, when performance matters.
4) Diameter is usually your biggest lever
Small diameter changes can cause large pressure changes. A larger hose reduces velocity and can cut both friction and fitting losses. If a line is struggling, checking inside diameter (not nominal size) is often more effective than swapping pumps.
5) Picking a loss model that matches the fluid
Hazen-Williams is common for water-based site lines and uses a C value to represent internal condition. Darcy-Weisbach is more universal and uses viscosity, roughness, and Reynolds number. For non-water fluids, warm water, additives, or slurry, Darcy-Weisbach is typically the stronger choice.
6) Fittings and valves can dominate short runs
On compact sites, elbows, tees, quick-couplers, and valves can add more loss than straight pipe. Minor loss uses a summed K value multiplied by velocity head, so fast-moving flow makes fittings expensive. Counting components and adding custom K values reflects real installs.
7) From head to gauge pressure and power
Pressure follows from P = ρgH, so heavier fluids need more pressure for the same head. The calculator reports bar, kPa, and psi for field comparison. Power comes from Phyd = ρgQH, then rises further when efficiency is lower.
8) Field-ready checks and documentation
Compare results to pump curves at the required flow and add contingency for kinks, fouling, and routing changes. Verify pressure ratings for hoses and couplings. Exporting CSV supports procurement and checklists, while the PDF report helps commissioning and temporary works documentation.
FAQs
1) What pressure range is common for temporary dewatering?
Many small dewatering setups land around 1–4 bar, but lift, diameter, length, and fittings can push higher. Use the calculator with your actual layout and confirm against the pump curve at the target flow.
2) When should I choose Darcy-Weisbach?
Choose it for non-water fluids, temperature-driven viscosity changes, slurry, or whenever roughness and Reynolds effects matter. It is the most general method for engineering checks across different fluids and materials.
3) Why does diameter change pressure so much?
Diameter controls velocity. Higher velocity increases friction and fitting losses rapidly, especially in Darcy-Weisbach where losses scale with velocity squared. Upsizing a hose is often the quickest way to reduce required pressure.
4) How do fittings affect results?
Each elbow, tee, valve, or strainer adds a K value. The summed K multiplies velocity head, so many fittings can dominate short systems. Counting components usually beats using a single “rule of thumb” allowance.
5) What is “required discharge pressure” used for?
It represents minimum pressure needed at the endpoint, such as a nozzle, sprinkler, or tool. The calculator converts that pressure to head and adds it to elevation and friction so the pump target is complete.
6) Why might my gauge not match the calculated pressure?
Gauge location matters. Differences also come from suction conditions, elevation between gauge and outlet, hose kinks, clogged filters, and actual diameter or roughness differing from assumptions. Use the head breakdown to pinpoint the driver.
7) Should I add a safety margin?
Yes. Site routing changes, fouling, and wear increase losses. Add contingency to head, then verify the pump can still meet the required flow on its curve. Always confirm hose and coupling pressure ratings.