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PUREFLOW BIO / ENGINEERING FIELD GUIDE

Gravity-Feed Pipework DesignSlopes, Levels and Air Locks

How to design gravity-fed pipework for filters: pipe size, fall, avoiding air locks and keeping solids moving.

Explore the process ↗Open the workbench
6 MIN GUIDEUPDATED NOVEMBER 2026
Reference illustration for Gravity-Feed Pipework Design: Slopes, Levels and Air LocksEQUIPMENT REFERENCE
Equipment reference illustration. Confirm the supplied model configuration and installation arrangement from its approved documentation.
01Understand the mechanismInspect the relevant process stages.
02Review the operating dutyKeep assumptions and measured values visible.
03Prepare the next decisionUse the guide, tools and project checks.
INTERACTIVE PROCESS ATLAS

See the mechanism.
Understand the duty.

Select a route or a stage to inspect the process. The cutaway explains the equipment and water environment; it is a teaching illustration, not a project drawing.

Swipe horizontally to inspect the equipment. Stage buttons below also centre the selected component.
Pump and pipework hydraulic dutyPUREFLOW / INTERACTIVE PROCESS ATLASCONCEPT LAYOUT · NOT TO SCALESUCTION CONDITIONSIMPELLER / VOLUTEMEASURE THE DUTYTREATMENT RESISTANCEACTUAL FLOW COMES FROM THE PUMP AND SYSTEM CURVESMotion explains the process; it is not a measured flow rate or biological time model.
The pump transfers hydraulic energy to the water. Its headline flow is not the same as the delivered system flow.
Selected process stage

Supply the pump

Check the complete pump and system duty.

How it works

Maintain the approved suction arrangement and avoid dry running or air ingress.

What to establish
  • Check the complete pump and system duty.
  • Use internal pipe dimensions and measured operating flow.
  • Review supply conditions, protection and service isolation.

Continue this guide ↗

Motion explains direction and mechanism; it does not represent measured performance. Geometry, stage order, pipe routes and equipment configuration are conceptual. Use the approved project design, operating instructions and verified model data.

Key takeaways

  • Set the levels: Draw the water level in the tank, the filter inlet and the outlet.
  • Pipe size: Use larger pipe for gravity lines so velocity stays low and friction is small.
  • Avoid air locks: Slope pipes continuously, avoid high points and use a vent where needed.
  • Keep solids moving: Provide enough velocity to carry solids without settling, and avoid long flat runs.
Reference illustration for Gravity-Feed Pipework Design: Slopes, Levels and Air Locks
Equipment reference visual; not evidence of a completed installation.
THE SHORT ANSWER

Set the levels

Draw the water level in the tank, the filter inlet and the outlet. The filter inlet must sit below the tank water level with enough head to push the flow through.

Gravity-Feed Pipework Design - Pureflow Bio
Reference visual. Equipment configuration and project details must be confirmed separately.
GRAVITY-FED OR PUMP-FED

Pipe size

Use larger pipe for gravity lines so velocity stays low and friction is small. Narrow pipe limits flow and raises the tank level.

PLANNING WORKBENCH

Work with your own numbers.

Use the tools below to explore the relevant arithmetic. Enter measured values or declared assumptions. An estimate does not establish equipment capacity, biological performance or a safe operating limit.

Pipe velocity check

Calculate mean velocity using actual flow and the pipe’s internal diameter.

Assumptions and limits

Internal diameter differs from nominal outside size. Velocity alone does not prove gravity capacity, solids transport, pressure loss or freedom from air locks.

—Mean pipe velocity · m/s
—Cross-sectional area · cm²
Enter your values, or load the labelled arithmetic example. No design values are pre-filled.
FormulaVelocity = (flow ÷ 3,600) ÷ [π × (diameter ÷ 1,000)² ÷ 4].
Convert units before you calculate
Choose units and enter a value.

Planning arithmetic · inputs remain visible for review · example values are not operating recommendations

GRAVITY-FED OR PUMP-FED

Avoid air locks

Slope pipes continuously, avoid high points and use a vent where needed. Keep bends smooth.

GRAVITY-FED OR PUMP-FED

Keep solids moving

Provide enough velocity to carry solids without settling, and avoid long flat runs. See installation checklist.

GRAVITY-FED OR PUMP-FED

Add overflow protection

An emergency overflow protects the tank if a pipe blocks.

Pureflow Bio equipment for this

Standard drum filters (RDF) →Automatic solids removal.Pro drum filters →Compact pump-fed drum filters.
PROJECT REVIEW

Coordinate the levels and losses

Use these questions to prepare a project brief or an operating review. Check an item only when the information has been recorded for your installation.

0 of 3 checked

This checklist is a working aid in the current page session, not a saved maintenance record.

QUESTIONS

Gravity-Feed Pipework Design FAQ

How much slope do I need?

Enough for steady flow without standing water. Ask your supplier for guidance for your pipe size.

Can I mix gravity and pump?

Yes. Many systems gravity-feed the filter and pump the clean water back.

KEEP READING
Gravity or pump-fed→Drum filter installation→Pump head loss→Sump and Pump Station Design: Where the Clean Water Goes ↗

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