How To Size A Vertical Turbine Pump for Deep-Well Water Intake

Size a line-shaft vertical turbine pump from the required flow and the water level measured while the well is pumping at that flow. Then calculate total dynamic head, check where the pump can be set in the well and verify the duty on the supplier's curve. A pump can meet the calculated flow and head and still be unsuitable if the bowls do not fit the casing or if the intake loses submergence during drawdown. Keep the hydraulic duty and the physical setting on the same specification sheet.

Start With the Pumping Test and Required Flow

Record the intended operating flow alongside the well's pumping test results. The static water level is the level before pumping, and the pumping water level is the level measured while the well is delivering a stated flow. The drop between the two levels is drawdown. Include the test duration and the water level trend, particularly if the water level was still falling at the end of the test.

Check whether the tested yield and pumping level support the project's demand. If a site needs a brief peak flow above its normal demand, define that peak and how long it lasts. A pump's rated capacity describes the equipment. The well test and site data establish how much water the source can deliver under the stated conditions.

Illustrative well and discharge data

If a step test provides results at several flows, keep each flow paired with its measured pumping level. Two wells with the same static level can draw down by very different amounts under load. For a station with nearby production wells, tell the supplier which wells were running during the test and which combinations are expected in service. A measurement taken under one set of conditions gives the reviewer a traceable starting point for judging the other scenarios.

Put all elevations on one datum, such as the top of the well casing. A drawing may show the delivery tank relative to finished grade while the well log reports water depth below the casing rim. Convert both to the same datum before adding the elevation differences. Record the datum in the RFQ so the supplier can reproduce the duty calculation.

Calculate Total Dynamic Head at the Design Flow

For the open-well-to-open-tank example, the two water surfaces are exposed to atmospheric pressure and their velocities can be treated as negligible. The elevation difference is 35 m + 12 m = 47 m. Adding 8 m of losses gives a total dynamic head (TDH) of 55 m at 100 m³/h. These values are illustrative.

If the discharge feeds a pressurized header, add the required pressure head at the defined destination and include the pipe, valve and fitting losses to that point. Agree with the supplier on the curve reference and how column losses are accounted for, so each loss appears once. Recalculate when the flow changes because friction losses vary with flow. Recalculate the elevation head when the expected pumping level or destination level changes.

Build a Duty Range From the Same Calculation

Run the calculation for the conditions the pump will actually see. In the example, a pumping water level of 30 m below the wellhead gives 50 m of total head at the same 100 m³/h, while 40 m below gives 60 m. The tank level and pipe loss are held constant in those two comparisons. The resulting 50–60 m range describes the system head at the specified flow. A fixed-speed pump will generally deliver different flows at the two water levels. Plot the system curves to estimate those operating points.

Where the design has two operating flows, prepare a separate line for each. Use the expected pumping water level for that flow and recalculate the losses through the pipe, valves and fittings. Where the discharge pressure varies, record the minimum and maximum expected pressure and identify which values can occur together. That gives the supplier a duty envelope that reflects site operation.

Check Pump Setting Depth and Bowl Clearance

The pump setting places the intake and bowls at the intended depth in the well. Review the lowest expected pumping water level, the manufacturer's minimum submergence requirement at the proposed flow, and the well construction. Mark the casing transitions, screen interval and well bottom on the same drawing. Check the clear bore against the supplier's dimensions and allow for the specified installation clearances.

Ask the supplier to state which part of the assembly its setting dimension refers to. Show the intake elevation and the available clearance on the drawing, then confirm the shaft and column arrangement for that setting. If the well has a history of sand production, provide the available water-quality data and well records before finalizing intake placement and materials.

Review Submergence and Suction Conditions Together

Submergence is the depth of water above the intake at the operating condition. A minimum submergence check addresses the intake's ability to draw water under the proposed conditions. A net positive suction head check compares the head available at the pump inlet with what the pump requires at that flow, using the applicable margin. Ask the supplier to state the basis for both checks, including the flow, water temperature, lowest expected pumping level and intake reference elevation.

For a simple geometry check, an intake shown at 46 m below the wellhead has 6 m of water above it when the pumping level is at 40 m. That calculation tells the team what is available at that setting. Compare it with the requirements for the proposed bowl assembly. If additional submergence is needed, review a deeper setting against casing clearance, the screen position, bottom clearance and the revised column arrangement before changing the drawing.

Match the Duty Point to the Pump Curve

Use 100 m³/h at 55 m to screen candidate bowl assemblies and stage counts. On the curve, check the head, efficiency and power at the duty, then review where the pump and system curves intersect across the expected range of water levels. Ask the supplier to identify the allowable operating region and the maximum power demand within the planned operating range. If variable-speed operation is planned, request the curves or operating limits for the intended speeds.

The WY PUMPS VHS vertical turbine pump is an example of a line-shaft configuration with a bowl assembly that can be multistaged. For a project specification, request the proposed bowl model and stage count, a dimensional drawing, and the curve for the offered configuration.

Review the Selected Curve and Motor Together

Check where the design point falls relative to the best efficiency point and the operating range recommended for the offered pump. When the system has lower head, the intersection on a fixed-speed curve may move toward higher flow. Check the absorbed power there and verify whether the well can sustain the resulting flow. When the system has higher head, check that the flow still serves the process and that the pump remains in its permitted operating region.

The published hydraulic coverage charts are useful for identifying candidate ranges. A quotation should include the curve for the actual bowl model, speed, impeller selection and number of stages being offered. Ask for the power curve and the supplier's motor selection basis. When reviewing a variable-speed proposal, check the lowest and highest expected speeds with the actual system curves, especially if the station must maintain pressure across changing water levels.

Prepare a Deep-Well Pump RFQ

• Required normal and peak flow, operating schedule, and expected seasonal water levels.

• Pumping test flow, water levels over time, test duration and recovery records if available.

• Discharge elevation and destination pressure, pipe and valve data, and the calculated duty points.

• Well drawing, casing clear internal diameter, casing transitions, screen and bottom elevations, and any alignment survey.

• Water temperature, sand or suspended solids data, and any relevant water chemistry.

• Electrical supply, control method, available lifting clearance, and requested drawing and curve deliverables.

Submit your well data with the intended flow and discharge conditions so the proposal can be checked against the same assumptions used in your calculation.

Bring the Well Drawing and Pump Curve Together

A defensible selection includes the pumping test, the head calculation, the proposed intake elevation and the curve for the actual pump being purchased. In the example, 100 m³/h at 55 m starts the selection. The rest of the review establishes how the pump behaves when the water level changes and whether the offered assembly fits and stays submerged. When reviewing an offer from WY PUMPS or evaluating several bids, keep those four items together. A reviewer can then trace each selection assumption back to the well, the system or the equipment.

Frequently Asked Questions

Can the static water level be used for an initial estimate?

It can help establish the site elevation reference. For sizing, use a pumping level tied to the intended flow and review how that level could change during prolonged operation or in a dry season.

How does a deeper setting affect total dynamic head?

If the pumping and destination water levels stay the same, the elevation lift between them stays the same. A longer column can change friction losses and the mechanical arrangement. Check both in the revised proposal.

What should I ask for when comparing two quotations?

Request curves for the offered speed and stage count, power demand across the operating range, and the dimensions and setting assumptions. Compare the offers at identical flow and head conditions.

Does a higher head requirement always mean adding another stage?

Stage count is one design variable. The bowl model, speed and impeller selection also affect the available head and the operating range. Ask the supplier to compare configurations at the actual flow before deciding on a stage count.