Content checked against the referenced Spirax Sarco technical information: 18 July 2026. Product availability, connections and certified limits can vary by market and revision, so confirm the current regional documentation before specifying equipment.
When does a steam system need a condensate pump?
A Spirax Sarco condensate pump is used when recovered condensate needs additional pressure to overcome lift, return-line backpressure or changing process conditions. A steam trap can discharge condensate only while the pressure upstream of the trap is high enough to overcome the pressure in the return system. On temperature-controlled heat exchangers, the control valve may reduce steam pressure as the process load falls. If the available differential pressure disappears, condensate can back up into the equipment. This condition is commonly known as stall.
A condensate pump provides the pressure needed to move condensate into the return line when gravity drainage or trap differential pressure is insufficient. The right arrangement depends on whether condensate arrives from a vented receiver, a pressurised process, a vacuum duty or a modulating heat exchanger.
Why recover hot condensate?
Condensate contains treated water and useful heat. Returning suitable condensate to the boiler house can reduce make-up water, water-treatment demand and the energy needed to heat incoming feedwater. Effective removal also supports stable heat transfer and helps avoid waterhammer, corrosion, noise and equipment damage associated with retained condensate.
Start with the wider condensate recovery guide when the return network, flash steam, line sizing and receiver arrangement must be assessed as one system.
Compare Spirax Sarco condensate pump solutions
Choosing a Spirax Sarco condensate pump begins with the drainage problem rather than the nominal pipe size. Use the following comparison as an initial route to the appropriate product family. Final selection requires a verified duty and the current technical information for the exact model and connection standard.
| Solution | How it operates | Typical application direction | Key checks |
|---|---|---|---|
| MFP14 condensate pump | A pressure-powered mechanical pump uses motive steam or compressed gas to discharge condensate in cycles. | Lifting condensate, overcoming return-line backpressure, draining vented receivers or pumping from equipment where a separate trapping arrangement is appropriate. | Motive pressure, total backpressure, filling head, condensate load, receiver venting, check valves and material. |
| APT14 automatic pump-trap | An automatic pump-trap combines trapping and pressure-powered pumping in one body and changes operating mode as differential pressure changes. | Modulating heat exchangers and other process equipment exposed to stall, including duties that may operate under vacuum. | Equipment pressure through the load range, stall point, motive pressure, backpressure, installation head and maximum condensate load. |
| Electric condensate pumps | An electric pump and receiver collect condensate and return it to the boiler-feed or condensate-return system. | Vented multi-point condensate collection and packaged return duties where electrical power and suitable hot-condensate pump design are available. | Condensate temperature, receiver capacity, net positive suction head, pump duty point, controls, standby philosophy and venting. |
| Packaged pump unit | A pre-engineered assembly combines the pump with the receiver, valves, strainers, check valves and connecting pipework required by the selected arrangement. | Projects that benefit from a coordinated package, reduced site assembly and a defined single, duplex or duty/standby configuration. | Package scope, receiver sizing, peak load, redundancy, motive utility, vent route, discharge line and site dimensions. |
Pressure-powered condensate pumps
A pressure-powered Spirax Sarco condensate pump uses steam, compressed air or another suitable pressurised gas as the motive fluid. A float-operated mechanism alternately fills and discharges the pump body. Because the pumping action is mechanical, these units can suit hot condensate duties and locations where an electric motor at the pump is undesirable.
The mechanical condensate pump range includes separate pump and automatic pump-trap routes. The Spirax Sarco MFP14 is available in material and size variants for different duties. Its capacity depends on motive pressure, backpressure, filling head, pump size and motive-fluid choice, so it should be sized from the complete operating data rather than nominal pipe size alone.
Automatic pump-traps for stalled equipment
An automatic pump-trap drains condensate as a steam trap while positive differential pressure is available. When equipment pressure falls below the return-system pressure, the same unit uses motive steam to pump the accumulated condensate. This makes the arrangement particularly relevant to modulating heat exchangers, where steam pressure changes with the process demand.
The Spirax Sarco APT14 automatic pump-trap provides a direct product route for APT14, APT14HC and APT14SHC duties. The correct model depends on load, connections, body material and site conditions. An automatic pump-trap is not a substitute for calculating the stall point or checking the return-line backpressure.
Electric condensate recovery units
Electric condensate pumps are commonly applied to vented receivers that collect condensate from several sources. They can provide a familiar duty/standby arrangement and level-based control, but the pump and receiver must be designed for the condensate temperature and available suction conditions. Hot condensate can flash as pressure falls, so net positive suction head and receiver venting need particular attention.
Review the Spirax Sarco electric condensate pump range when the duty is a conventional receiver-led return system rather than a stalled pressurised process.
Engineering data needed for condensate pump sizing
Before sizing a Spirax Sarco condensate pump, record the full operating duty at minimum, normal and peak load. The following inputs determine pump type, capacity, receiver arrangement and discharge performance.
| Input | Why it matters |
|---|---|
| Maximum and minimum condensate load | Establishes required capacity and whether variable or peak loads control the selection. |
| Condensate temperature and pressure | Affects flash steam, receiver design, pump suction conditions and material selection. |
| Equipment pressure across the load range | Shows whether a heat exchanger will stall and when pump operation is required. |
| Return-line pressure | Forms part of the total backpressure the pump must overcome. |
| Vertical lift | Adds static head to the discharge duty. |
| Discharge-line losses | Adds frictional resistance, including the effect of fittings and cyclic pump flow. |
| Available filling head | Influences the capacity of a pressure-powered pump and the receiver layout. |
| Motive steam or compressed-air pressure | Must be sufficient to overcome total backpressure and operate the selected mechanical pump. |
| Electrical supply and control philosophy | Defines motor, level control, alarms, standby operation and site integration for electric units. |
| Connection, material and compliance requirements | Ensures the selected construction suits the piping standard, environment and project specification. |
Worked MFP14 sizing example
The following calculation illustrates how motive pressure, lift, return pressure and filling head interact. It uses the worked duty published in the MFP14 technical information; it is not a substitute for checking the current capacity chart for a live project.
- Duty: 1,500 kg/h condensate load, 5.2 bar g motive steam, 9.2 m vertical lift, 1.7 bar g pressure in the return line and 0.15 m filling head.
- Convert return pressure to head: 1.7 ÷ 0.0981 = approximately 17.3 m.
- Calculate effective head before pipe friction: 9.2 + 17.3 = 26.5 m.
- Read the capacity chart: the published example gives approximately 2,400 kg/h for a DN50 pump at the chart reference filling head.
- Apply the filling-head correction: the 0.15 m correction factor is 0.75, giving 2,400 × 0.75 = 1,800 kg/h.
- Check the result: 1,800 kg/h exceeds the 1,500 kg/h stated load in the example. A final design must also include discharge-pipe friction, operating margin and the current document revision.
For receiver-based systems, see pumping condensate from vented receivers. A final selection should be checked against current capacity charts and installation instructions.
Installation and commissioning checks
- Confirm the flow direction, filling head and orientation shown in the model-specific installation manual.
- Provide the correct inlet and outlet check valves for a pressure-powered pump and keep their pressure drop in the sizing calculation.
- Size and route receiver vents safely; never treat the vent as an optional small-bore connection.
- Keep motive-fluid pipework clean and provide the required isolation and straining arrangement.
- Check that total backpressure remains below the available motive pressure throughout operation.
- Allow access for inspection of the mechanism, valves, strainers and level controls.
- Commission the complete system at low and high load where practicable, checking cycle rate, receiver level, discharge behavior and signs of waterhammer.
Common condensate pumping problems
The pump fills but does not discharge
Check motive-fluid availability, total backpressure, inlet and outlet check-valve direction, motive inlet valve operation and the exhaust path. A rise in return-system pressure can prevent a pump from completing its discharge stroke even when the original selection was correct.
The pump cycles but condensate backs up
Compare the observed cycle rate and load with the selected capacity. Insufficient filling head, excessive backpressure, restricted check valves, an undersized receiver or a peak load above the design duty can reduce effective capacity.
A heat exchanger floods at part load
Check for stall. The steam pressure downstream of the control valve may have fallen below condensate return pressure, leaving a conventional trap without enough differential pressure to drain. The remedy must address the complete drainage arrangement, not simply replace the trap with a larger one.
An electric condensate pump is noisy or loses capacity
Review condensate temperature, receiver venting, available suction head, inlet restrictions and the pump duty point. Flashing at the pump inlet can lead to cavitation-like symptoms and unstable performance.
Frequently asked questions
Is a condensate pump the same as a steam trap?
No. A steam trap uses the pressure difference across it to discharge condensate while retaining steam. A condensate pump adds energy to move condensate against lift or backpressure. An automatic pump-trap combines both functions for duties where differential pressure can vary or disappear.
Can a pressure-powered condensate pump run without electricity?
Yes. A suitable pressure-powered pump can operate from motive steam or compressed gas and uses a mechanical float-and-valve mechanism. Controls or monitoring accessories may still require power if they are included.
How is condensate pump backpressure calculated?
Include pressure in the return line, static lift and discharge-pipe friction. For a pressure-powered pump, use the manufacturer's sizing method because cyclic discharge flow affects pipe-loss calculations.
Should I choose an MFP14 or an APT14?
Choose by system function. MFP14 is a separate pressure-powered pump for condensate or other compatible liquids. APT14 combines pumping and trapping for equipment that must drain across changing differential-pressure conditions. The site arrangement and verified duty determine the correct route.
Official technical information and installation documents
Use the current product document for certified pressure and temperature limits, connection options, materials, capacities, installation requirements and spare parts. These official references were accessible when this page was reviewed:
- MFP14, MFP14S and MFP14SS automatic pumps — technical information (PDF)
- APT14, APT14HC and APT14SHC automatic pump-traps — technical information (PDF)
- MFP14, MFP14S and MFP14SS automatic pumps — installation and maintenance instructions (PDF)
- Spirax Sarco pressure-powered condensate pump range
- Spirax Sarco electric condensate pump range
Plan the complete condensate return system
Condensate pump selection is part of a wider return-system design. Confirm steam-trap duties, receiver capacity, flash steam, return-line sizing, waterhammer risk, controls, venting, maintenance access and boiler-house integration before ordering equipment. Explore the complete condensate and heat recovery product range, or contact Spirax Sarco with the operating data for application review and sizing support.