First choose: run or shut down
A pump can tolerate cold water while the filter, UV chamber, check valve or exposed return line connected to it cannot. That is why the decision applies to the whole circuit, not just the pump.
| Plan | It can make sense when | Main risk to control |
|---|---|---|
| Run all winter | Every component is rated for expected temperatures, flow can stay continuous and the pond is accessible for checks | A blockage, power outage or ice dam can stop flow and leave water trapped in exposed equipment |
| Shut down | Hard freezes are normal, equipment is not frost-protected, or monitoring will be difficult | Water left in housings, low spots, valves or rigid plumbing can freeze and expand |
| Partial winter system | The main waterfall circuit is stored while a separate shallow aerator or winter-rated pump handles gas exchange | The winter device still needs correct placement, electrical protection and regular checks |
OASE’s current winter guidance makes the product-specific distinction clear: some frost-protected pumps can continue operating, while non-frost-protected pumps and equipment containing glass or plastic should be stored in water in a frost-free location. Aquascape likewise directs owners who shut a pond down to remove the pump and store external pressurized filters frost-free after draining them.
Map the water path before taking it apart
Photograph the installation and trace the water from the pond to the return. Label unions, valves, UV direction and electrical plugs. This takes a few minutes and prevents a spring puzzle.
- Pump or skimmer vault
- Check valve and unions
- Mechanical or biological filter
- Pressurized filter and backwash valve, if present
- UV clarifier and its quartz sleeve
- Above-ground pipe, hose, waterfall box and low spots
Mark anything that can hold water after the pump stops. A low loop of hose or closed valve can remain full even when the filter looks empty.
A careful shutdown sequence
- Stop feeding the system with new debris. Remove leaves around the skimmer and pump intake so the final cleanup is manageable.
- Switch off and unplug the pump and UV. Disconnect power before reaching into the pond or opening equipment. Use the equipment’s approved disconnect procedure.
- Close or open isolation valves as the manual requires. Relieve pressure in a pressurized filter before loosening a clamp or union.
- Drain the circuit. Open drain ports and remove drain plugs. Give hoses and exposed plumbing a continuous path to empty; do not rely on gravity if a low spot traps water.
- Remove and clean components. Rinse screens, impellers and filter housings with clean water. Avoid detergents or chemicals not approved by the manufacturer.
- Store or protect each part. Keep removable equipment in a frost-free place using the wet or dry storage method in its manual.
- Secure the open system. Cap or screen plumbing openings so animals and debris cannot enter, without sealing water inside.
Pump: clean the intake and follow its storage rule
Remove plant fibers, string algae, grit and snail shells from the intake cage. If the manual permits access, inspect the impeller area and O-rings without forcing brittle plastic parts. Look for cord damage, swelling, cracks and mineral deposits.
Storage advice is not universal. Some pumps are stored submerged in a clean bucket of water to protect seals; other designs are cleaned, dried and stored frost-free. Aquascape’s shutdown guidance specifies submerged storage for its pump setup, while its AquaForce instructions say to clean the pump and cage screens and keep the unit frost-free. The exact model manual wins.
- Never lift a pump by its power cord.
- Do not use oil, grease or descaler unless the manual approves it.
- If wet storage is required, label the container and check that the water has not evaporated.
- Store small fittings, O-rings and drain plugs in a labeled bag beside the equipment.
Filter: drain water without destroying useful media
A filter housing that freezes while full can crack. Empty the vessel, backwash or rinse it as directed and leave drain ports in the specified winter position. Pressurized filters may have a dedicated winter setting; never move a multiport valve while the pump is running unless the manual explicitly allows it.
Filter media needs a deliberate plan too. A complete shutdown means the established biological community will not function as it did during warm-water operation. Do not assume that keeping dirty media sealed in stagnant water preserves it. Follow the filter maker’s cleaning and storage directions, and expect to monitor water quality carefully when the system restarts.
For waterfall filters that remain outdoors, confirm whether the housing and connected flexible pipe are designed for normal freeze-thaw conditions. Drain any component the manufacturer does not rate to hold freezing water.
UV clarifier: power off, drain and protect fragile parts
A UV clarifier combines water, electricity, a lamp and often a fragile quartz sleeve. Unplug it before service and never view an operating UV-C lamp directly. Allow the unit to cool, relieve system pressure and drain it before opening.
- Inspect the quartz sleeve for cracks and mineral scale without twisting or prying it.
- Keep the sleeve and lamp where they cannot roll, freeze or be struck.
- Record the lamp’s installation date; output can decline even if the lamp still glows.
- Replace seals only with parts specified for the model, and do not pinch an O-ring during reassembly.
Some manuals call for removal of the lamp or quartz tube; others direct owners to remove and store the whole clarifier. Use the written procedure for your unit.
Plumbing: find the water that gravity misses
Rigid fittings, check valves, UV chambers and exposed pipe are vulnerable when water freezes inside them. Disconnect unions and open drains so water has an exit. If a line cannot drain naturally, use only the winterization method and pressure limits approved for that plumbing system; uncontrolled compressed air can damage fittings or create a projectile hazard.
After draining, protect open pipe from leaves and rodents. Do not glue or permanently cap anything you will need for spring priming. Photograph valve positions and attach a note describing what must be reopened.
If the system will run all winter
Leaving equipment on is not a set-and-forget choice. Confirm the pump’s minimum operating temperature, the freeze rating of every filter and UV component, adequate water depth over the intake, and a route that cannot spill the pond if ice redirects the waterfall.
- Check flow after snow, wind, freezing rain and power interruptions.
- Keep the intake clear and maintain the pond’s water level.
- Watch for ice that diverts return water outside the liner.
- Use outdoor-rated, GFCI-protected power and keep connections out of standing water.
- Have a shutdown and drainage plan ready in case circulation stops.
A winter waterfall is not automatically beneficial. In severe cold it can expose more water to cold air, create ice dams and increase evaporation. Separate the desire for appearance from the fish pond’s actual gas-exchange needs.
Make spring restart easier
- Inventory the pump, drain plugs, unions, O-rings, UV sleeve and lamp before storage.
- Photograph wiring routes and valve positions.
- Write down repairs and replacement parts needed; do not defer a damaged cord.
- In spring, inspect and reassemble before filling the filter or applying power.
- Prime as directed, check every union for leaks and confirm water returns to the pond.
- Monitor fish behavior and water quality as biological filtration re-establishes.
Complete the cold-weather plan
Equipment protection is one part of winter care. Use the pond-netting guide before peak leaf drop, make feeding decisions with the measured water-temperature guide, and compare a de-icer with a winter aerator before the surface freezes.