Winterizing a Self-Priming Pump: How to Drain the Pump Casing and Piping Properly

 Winterizing a Self-Priming Pump: How to Drain the Pump Casing and Piping Properly

When winter temperatures fall below freezing, self-priming pumps installed outdoors may face a serious risk of freeze damage during extended shutdowns.

Some users assume that draining the pump casing is sufficient to protect the entire system. However, residual liquid may remain inside suction pipes, discharge lines, valves, strainers, and other low points.

When this trapped liquid freezes and expands, it can damage pump housings, pipelines, valves, and sealing components.

So, how should a self-priming pump be prepared for winter shutdown? More importantly, how should the pump casing and connected piping be drained separately?

1. Why Is Winter Drainage Important for Self-Priming Pumps?

A self-priming pump does not necessarily drain itself automatically after shutdown.

Depending on its design, liquid may remain inside the pump casing, priming chamber, or internal flow passages.

Some self-priming pump designs also require a certain amount of liquid to remain in the casing during normal operation. Before winter storage, the manufacturer’s drainage instructions should therefore be followed.

When residual water freezes, its expansion may create pressure inside enclosed spaces, potentially damaging the pump casing or internal components.

Winter protection should address all liquid-retaining areas, not just the main pump chamber.

2. Draining the Pump Casing: What Should Be Checked?

The pump casing is the first area to consider during winter preparation.

Locate the designated drain port

Many self-priming pumps have a drain plug or dedicated drainage opening.

After shutting down and isolating the power supply, locate the drain point according to the pump manual and allow the liquid to drain completely.

Check internal low points

Some pump designs contain recesses or internal passages where liquid may remain even after the main drain opening has been opened.

If gravity drainage is insufficient, follow the manufacturer's recommended procedure rather than dismantling components unnecessarily.

Consider mechanical seals and auxiliary components

Pumps equipped with mechanical seals, cooling connections, or auxiliary piping may have additional liquid-retaining areas.

Their drainage requirements depend on the specific pump configuration.

3. Draining the Piping: Why Is It Often Overlooked?

Draining the pump casing does not mean that the entire pumping system is empty.

Connected piping may extend over a considerable distance and contain several low points.

Suction piping

Inspect the suction line, particularly its low points, elbows, strainers, and foot valves.

A foot valve is designed to prevent liquid from flowing backward, but it may also retain liquid inside the suction line.

Additional drainage arrangements may be required depending on the system layout.

Discharge piping

Discharge lines can also retain water after shutdown.

Pay particular attention to horizontal sections, downward bends, and low-lying pipe sections.

Use designated drain valves where available.

Valves and strainers

Check valve chambers, filter housings, and other fittings for trapped liquid.

A strainer may retain a considerable amount of water inside its housing even when the main pipeline has been drained.

4. Commonly Overlooked Areas During Winter Shutdown

Several components deserve additional attention:

- Pump casing drain plugs: Check that the drainage passage is not blocked.

- Suction foot valves: Determine whether the valve prevents complete drainage.

- Strainers: Remove trapped liquid from the housing according to the maintenance procedure.

- Discharge check valves: Check internal cavities where water may remain.

- Mechanical seal auxiliary lines: Follow the manufacturer's drainage instructions.

The exact procedure depends on the pump construction and piping arrangement.

5. How to Protect a Self-Priming Pump Against Freezing

Drainage is one important method of winter protection, but other measures may also be necessary.

Provide suitable insulation

Outdoor pumps may require protective enclosures or insulation to reduce exposure to low temperatures.

Consider heat tracing

For systems that must remain operational, properly designed heat tracing may help maintain suitable fluid temperatures.

Evaluate antifreeze compatibility

Antifreeze should not be introduced without confirming compatibility with the pump materials, seals, and process requirements.

Protect drained openings

After drainage, protect openings against dirt, debris, and unwanted contamination while following the manufacturer's storage instructions.

Inspect before restarting

Before returning the pump to service, check for freeze-related cracks, deformation, damaged seals, and electrical problems.

6. What Should Be Checked Before Restarting After Winter Storage?

A pump that has been shut down for an extended period should not immediately be operated at full load.

Before restarting, check:

1. Pump casing, flanges, and connected pipes for cracks or deformation.

2. Drain plugs and sealing components for correct installation.

3. Suction filters and foot valves for blockage.

4. Motor, cables, and electrical protection devices for abnormal conditions.

5. Required priming liquid level and priming procedure.

6. Suction and discharge valves for correct operating positions.

Once these checks are completed, restart the pump according to the manufacturer's instructions and observe its operating condition.

Never run a self-priming pump dry unless its design specifically permits such operation.

Conclusion

Winterizing a self-priming pump requires more than simply draining the pump casing.

Residual liquid may remain in suction pipes, discharge lines, valves, strainers, and auxiliary components.

Shanghai Shangcheng Pump & Valve recommends preparing a winter drainage procedure based on the actual pump design and piping arrangement.

By treating the pump casing and connected piping as separate drainage areas, users can reduce freeze-related damage and improve the reliability of equipment during the next operating season.