To winterize a sand filter for an above-ground pool, the essential job is to remove water that could freeze inside the filter, valve, pump, hoses, and connected plumbing. In most conventional sand-filter systems, you backwash the filter, shut the system down, relieve pressure, open the tank drain, drain the plumbing, and leave the multiport valve in the manufacturer-specified winter position. The sand normally stays in the tank unless the filter’s own manual specifically tells you to remove it.
That last point matters because above-ground pool equipment is not all built the same way. A permanent-style top-mount sand filter may be designed to remain outdoors, drained, with its sand bed undisturbed. Some portable sand-filter pumps, however, are intended to be emptied, dried, and stored indoors. Following a generic winterization checklist without identifying your filter design can therefore create unnecessary work or leave freeze-prone parts full of water.
What Winterizing a Sand Filter Actually Involves
A sand filter cleans pool water by directing it through a bed of filter media. Water remains inside the tank, valve passages, pump, hoses, and fittings during normal operation. If the system stays full when temperatures fall below freezing, that trapped water can become the damaging part of the system.
Manufacturer guidance reflects this risk. Pentair’s instructions for Sand Dollar and Cristal-Flo II top-mount sand filters tell owners in freezing climates to backwash, switch the pump off, move the control valve to its winterize position, remove the filter’s drain-port cap, and drain the system piping. The same manual says to leave the drain cap off during the shutdown period. You can review the Pentair sand-filter installation and user guide for the model-specific wording.
Hayward’s ProSeries guidance follows the same basic principle but shows why the valve instruction cannot be universal. Its winterizing section says to drain the tank completely, leave the drain cap off, and position the Vari-Flo valve pointer between two settings so water can drain from the valve. That differs from filters that have a dedicated WINTERIZE setting. The correct position is the one specified for your valve, not whichever label happens to appear in a generic checklist.
Before You Start: Identify Which Sand-Filter System You Have
Look for the manufacturer name, model number, and valve model on the filter tank, valve label, pump data plate, or original paperwork. This is more important than it may seem because the winter storage method can differ even between systems that both use sand.
Most conventional above-ground sand filters use a rigid tank with a top-mounted or side-mounted multiport valve. The tank often remains beside the pool during winter after it is fully drained. By contrast, some compact systems supplied with seasonal frame pools are designed to be disconnected and stored. Bestway, for example, instructs owners of certain sand-filter pumps to drain the tank, disconnect the hoses, remove the sand, dry the components, and store the filter in a dry location. Its current above-ground pool winterization guidance likewise tells owners to remove and dry the sand before storing the sand-filter pump.
| Filter setup | Typical winter approach | What to verify in the manual |
|---|---|---|
| Conventional rigid sand-filter tank | Drain water from the tank and plumbing; sand commonly remains in place. | Drain-cap procedure, valve position, pump drainage, and outdoor protection. |
| Portable sand-filter pump for a seasonal pool | The complete unit may need to be disconnected, emptied, dried, and stored. | Whether the manufacturer requires the sand to be removed and where the unit should be stored. |
| Multiport valve with a WINTERIZE position | Use the dedicated winter setting after the pump is off and drainage is underway. | Whether WINTERIZE is the required shutdown position for that exact valve. |
| Multiport valve without a winter label | Some manufacturers specify an inactive position between detents to help the valve drain. | The exact handle position; do not assume all valves should be left between settings. |
If you cannot identify the model, avoid disassembling the valve, removing the filter’s main drain fitting, or using compressed air until you have the correct instructions. The drain cap and the complete drain fitting may look similar on some tanks, yet removing the wrong part can release filter sand along with the water.
How to Winterize a Sand Filter for an Above-Ground Pool
The following sequence fits many conventional above-ground sand-filter systems. Treat it as a structured checklist, then apply the specific drain, valve, and storage instructions in your equipment manuals.
Electrical safety reminder: before disconnecting, draining, or servicing powered pool equipment, switch the pump off and isolate its electrical power as directed by the manufacturer.
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Backwash the filter before shutdown
Backwash while the circulation system is still assembled and able to operate normally. This flushes accumulated debris out of the sand bed before the filter sits unused for months. If your normal backwash procedure includes a rinse cycle, complete it according to the valve instructions.
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Turn the pump off before moving the multiport valve
Never change a standard multiport valve position while the pump is running. After the final backwash or rinse, stop the pump and prevent an automatic timer or controller from restarting it while you work.
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Relieve pressure in the filter
If the filter has a manual air-relief valve, open it after the pump is off. Wait for pressure to dissipate and for the pressure gauge to return to zero before loosening service or drain components. A pressurized pool filter should not be opened or disassembled.
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Disconnect and drain hoses or exposed plumbing
Above-ground systems often use flexible hoses between the pool, pump, and filter. Disconnect and drain them where the pool-closing method permits. Rigid plumbing must also be protected from trapped water according to the pool and plumbing design. Do not assume that opening the filter drain automatically empties every pipe connected to it.
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Open the filter’s winter drain correctly
Remove the drain cap or plug specified by the filter manufacturer and let the tank drain fully. On Pentair Sand Dollar and Cristal-Flo II filters, the manufacturer specifically warns owners to remove only the drain-port cap, because removing the entire drain fitting can allow sand to escape. Drainage may be slow because water must work its way through the sand bed.
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Put the multiport valve in its specified winter position
Use WINTERIZE if your filter manual calls for it. If the valve has no winter setting, follow the manufacturer’s alternative. For example, Hayward’s ProSeries manual instructs users to depress the Vari-Flo handle and position the pointer between two settings during winter so the valve can drain. Do not copy that technique to a valve whose manual specifies something different.
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Winterize the pump separately
The filter tank and pump are separate freeze-risk components. Remove the pump drain plugs or follow the pump’s own drainage procedure, then drain the pump housing, strainer chamber, and connecting hoses as applicable. Do not run the pump dry to force water out.
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Leave the system able to stay drained
For conventional filters whose manuals call for outdoor winter storage, keep the filter drain open as specified rather than reinstalling the cap after the tank empties. Store caps, plugs, seals, and other small removable parts in a labelled container or other safe location so they are available at spring start-up.
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Protect or store the equipment as the manual requires
A conventional filter that remains outdoors can be protected from weather with the type of cover recommended by its manufacturer. Pentair, for example, recommends a tarpaulin or plastic sheet over the pump and filter but says not to wrap the pump motor in plastic. Portable systems that are specified for indoor storage should be cleaned, dried, and moved to the stated storage environment instead.
Why the Final Backwash Matters
Backwashing reverses water flow through a sand filter so collected debris is lifted from the sand bed and discharged through the waste line. A final backwash is included in winterization instructions from several filter manufacturers because it removes much of the material the filter captured during the swimming season.
Backwash before dismantling hoses and draining equipment. Once the pump and water connections are winterized, you no longer have a normal source of water and flow for an effective backwash cycle. If the valve instructions require a RINSE stage after backwashing, use it before final shutdown.
Do not move the multiport handle while water is flowing through the valve. Both valve and filter manufacturers commonly instruct users to stop the pump before changing settings. This protects the valve assembly and avoids abruptly redirecting pressurized flow.
How to Drain the Filter Without Losing Sand
Many rigid sand-filter tanks have a drain assembly near the bottom. The outer cap or plug allows water to leave the tank while an internal screen or fitting retains the filter media. The precise construction varies by brand and model, so the visible part should not be treated as a generic plumbing plug.
On Pentair’s Sand Dollar and Cristal-Flo II filters, removing the complete drain fitting rather than only its cap can let sand drain from the tank. That is one reason a stuck drain fitting should not automatically be attacked with more force. Confirm which piece is designed to come off, relieve filter pressure first, and use the service method specified for the tank.
After the correct cap is removed, drainage can take time because the sand bed restricts flow. The goal is not merely to stop seeing a strong stream from the drain. Give the tank enough time to empty, and make sure the upper side of the system can admit air if the filter design requires an air-relief valve to be opened.
What Position Should the Multiport Valve Be Left In?
There is no single correct label for every valve. Some multiport valves have a dedicated WINTERIZE position. On those models, the winter setting can leave internal passages open and may reduce pressure on the valve’s diverter seal. Pentair specifically states that the multiport valve on its Sand Dollar and Cristal-Flo II filters should remain in WINTERIZE during the shutdown season.
Other valves use a different method. Hayward’s ProSeries sand-filter instructions tell the owner to depress the Vari-Flo handle and rotate it so the pointer is between two positions, allowing water to drain from the valve, then leave it in that inactive position. Hayward’s separate VariFlo control-valve manual also describes winterizing by placing the handle pointer between detent positions.
Do not improvise by leaving the valve on CLOSED unless the manual specifically calls for it. A closed water path can work against the purpose of drainage if water remains trapped inside a valve or connected line. The safe rule is to use the shutdown position specified for the exact valve.
Should You Leave the Sand in the Filter Over Winter?
For many conventional rigid sand filters, yes. Winterization instructions from Pentair and Hayward focus on backwashing the filter, draining the tank, placing the valve correctly, and draining the pump or plumbing; they do not instruct owners to empty the sand bed as a routine winter step. In that type of filter, disturbing the media simply to winterize the tank is unnecessary unless your manual says otherwise or the sand needs separate service.
Portable filter-pump systems can be different. Bestway’s instructions for certain above-ground sand-filter pumps tell owners to drain the unit, disconnect its hoses, pour the sand out, dry the components, and store the filter in a dry place. The manufacturer’s 2023 sand-filter pump manual gives this storage procedure directly.
Therefore, the useful question is not simply “Does sand stay in over winter?” It is “How is this particular filter intended to be stored?” A heavy rigid tank intended to remain installed and a compact seasonal filter pump may both contain sand but have very different winter procedures.
Winterizing the Pump, Hoses, and Plumbing Around the Filter
A drained filter can still be connected to a pump or hose that contains enough water to freeze. Treat the complete circulation path as a system rather than stopping once water quits running from the filter tank.
Drain the pump using its own instructions
Many above-ground pool pumps have one or more drain plugs in the pump housing or strainer area. Their location and number vary. Remove only the plugs identified for winter drainage, allow the water to leave, and store the plugs safely if the manual says to leave them out during winter.
Do not use the pump itself as a drainage tool after the suction side has been disconnected or the water supply has dropped away. Running a pool pump dry can damage it. The final winter drainage stage should rely on the designed drains, disconnected hoses, gravity, or another method specifically approved by the manufacturer.
Empty flexible hoses completely
Flexible above-ground pool hoses can hold water in low spots even after they are disconnected at one end. Drain them fully, then store them in a way that prevents new rainwater or meltwater from collecting inside. Inspect hose cuffs and gaskets while the system is apart so damaged pieces are not rediscovered during spring start-up.
Do not assume the filter drain empties rigid plumbing
Water can remain in elbows, low points, check valves, heater connections, chlorinators, solar loops, or other equipment even when the filter tank is empty. If your above-ground pool has more than simple removable hoses, follow the winterization instructions for the complete circulation system. Complicated plumbing or buried runs may justify professional closing service because the filter’s drain port is not a substitute for properly draining those sections.
Do You Need Pool Antifreeze in a Sand Filter?
Do not automatically pour antifreeze into the sand-filter tank. For the common rigid filters discussed above, the main winterizing procedure is drainage. If the tank and connected equipment can be emptied as designed, adding liquid to the filter works against the basic goal of keeping freeze-prone water out.
Some equipment manuals allow a specific non-toxic propylene-glycol solution in a component that cannot be fully drained. Pentair, for example, gives such an instruction for installations where a pump cannot be drained and warns against other antifreeze types. That is a model-specific exception, not permission to use automotive antifreeze or to fill a sand filter with antifreeze.
If plumbing requires freeze protection beyond gravity drainage, use only a method and product approved for the equipment and pool application. Automotive antifreeze is not an appropriate substitute for pool or recreational-vehicle winterizing products.
Can a Sand Filter Stay Outside All Winter?
Many conventional sand-filter tanks are intended to remain installed outdoors after winterization, provided they are drained and protected as specified. Pentair recommends protecting certain sand filters and pumps with a tarpaulin or plastic sheet to reduce weather deterioration while specifically warning not to wrap the pump motor in plastic.
The important distinction is between a weather cover and sealing moisture inside the equipment. A cover should not defeat drainage, close the winter drain, or create a pocket that traps water. It should also remain secure enough that wind does not turn it into a load on the filter’s valve or plumbing.
Do not assume portable pool equipment can be treated the same way. If its manual calls for indoor dry storage, follow that instruction rather than covering it beside the pool. The manufacturer’s storage temperature and location requirements take priority over general outdoor-winterizing advice.
Common Winterizing Mistakes That Can Damage a Sand-Filter System
Removing the entire drain fitting instead of the drain cap
This can turn a routine drain into an unwanted sand-removal job on filters whose drain assembly is built to retain media. Identify the cap or plug specified in the manual and leave the fixed drain assembly alone unless it is being serviced intentionally.
Changing the multiport valve while the pump is running
The pump should be stopped before switching between FILTER, BACKWASH, RINSE, WASTE, RECIRCULATE, or winter positions. Moving the valve under flow can damage valve components and abruptly redirect water through the system.
Draining the filter but forgetting the pump
The filter tank can be perfectly drained while the pump housing still contains water. Winterize the pump as a separate component, and remember any attached strainer chamber or prefilter.
Reinstalling the drain cap for neatness
If the manufacturer’s shutdown procedure says to leave the filter drain cap off, reinstalling it can allow water from condensation, precipitation, or incomplete drainage to remain trapped. Store the cap and seal safely instead and reinstall them at spring start-up.
Assuming every filter should keep its sand
This is usually correct for conventional outdoor sand-filter tanks but not for every seasonal filter-pump system. Check the manual before committing either way. The same applies to valve position, storage location, and whether removable accessories stay attached.
Using compressed air without an approved procedure
Blowing out plumbing is not a harmless substitute for opening drains. Filters, pumps, hoses, and valves are pressure-containing components, and an unsuitable air source or incorrect setup can create hazardous pressure. If your pool layout requires line blowing, follow the equipment manufacturer’s specified method or use a qualified pool professional.
How to Know the Sand Filter Is Ready for Winter
A properly winterized conventional sand-filter system should no longer have a route for damaging amounts of water to remain trapped in the filter tank or its connected exposed equipment. Before covering or leaving the system for the season, check the work systematically rather than relying on the fact that the pool itself has already been closed.
- The final backwash has been completed.
- The pump is shut down and cannot restart unexpectedly.
- Filter pressure has been relieved before service points were opened.
- The correct filter drain cap or plug has been removed.
- The filter tank has had time to drain fully.
- The multiport valve is in the exact winter position required by its manual.
- The pump, hoses, and exposed plumbing have also been drained or stored as required.
- Any caps, plugs, seals, or removable parts are stored safely for spring.
- The filter is either weather-protected outdoors or stored indoors according to its design.
If one of these checks conflicts with your equipment manual, follow the manual. A filter-specific instruction is more reliable than a broad rule because it accounts for the tank drain, valve geometry, pump design, and storage method actually used on that system.
Spring Start-Up After a Sand Filter Has Been Winterized
Good winterization should make spring start-up simpler, but the equipment should not simply be switched on as found. Remove weather protection, inspect the filter tank, valve, hoses, seals, and pump for visible winter damage, then reinstall the drain caps and plugs that were intentionally left out.
Reconnect hoses or plumbing, restore the valve to the start-up position required by the filter manual, and prime the pump correctly before operation. Many sand filters require a backwash and rinse during start-up, particularly after the system has been opened, drained, or the media has been disturbed. Use the model’s start-up sequence rather than jumping directly to normal FILTER operation.
If the sand was removed for seasonal storage because the manufacturer required it, refill the tank using the correct media type, grade, and quantity for that model. Do not estimate the amount from another filter that looks similar; tank size, laterals, and specified media load vary.
Frequently Asked Questions
Do I have to remove all the sand to winterize an above-ground pool filter?
Not for many conventional rigid sand filters. Those systems are commonly winterized by backwashing and draining the water while the sand remains in the tank. Some portable sand-filter pumps are different and may require the sand to be removed, dried, and stored, so check the manual for your exact model.
Should I leave the sand-filter drain plug out all winter?
Leave it out if the manufacturer specifies that procedure. Pentair and Hayward instructions for several conventional sand filters explicitly say to leave the drain cap off during winter. Store the cap and its seal where they will not be lost or damaged.
Should the multiport valve be on WINTERIZE or between settings?
It depends on the valve. Some valves have a dedicated WINTERIZE position, while certain Hayward Vari-Flo valves are winterized with the pointer between detents. Use the position stated in the valve or filter manual rather than treating either method as universal.
Can I leave water in a sand filter if I cover it?
Not in a climate where the equipment can freeze. A cover can reduce weather exposure, but it does not stop trapped water inside the filter from freezing. The tank and connected freeze-prone equipment still need to be drained according to their instructions.
Do I need to replace the filter sand every spring?
Winterizing by itself is not a reason to replace sand in a conventional filter. Inspect performance and follow the media-maintenance guidance for your filter. Replace the media when the equipment instructions or its condition call for it, not simply because the tank was drained for winter.
Can I just disconnect the hoses and skip draining the filter tank?
No. Disconnecting hoses does not guarantee that water inside the sand bed and lower part of the tank will escape. Use the filter’s designated winter drain and allow the tank to empty according to the manufacturer’s instructions.
What to Remember Before Freezing Weather Arrives
The safest way to winterize sand filters for above-ground pools is to think beyond the tank itself. Backwash first, shut the pump down, relieve pressure, drain the correct filter port, protect the valve in its specified winter position, and remove water from the pump, hoses, and plumbing that could freeze.
Most conventional outdoor sand filters can keep their sand in place, but that rule does not apply to every portable filter-pump system. Confirm the model before deciding whether the media stays, whether the entire unit should be stored indoors, and how the multiport valve should be left.
The practical aim is simple: leave no freeze-prone water trapped where expansion can crack a tank, valve, pump housing, hose, or fitting. A few minutes spent checking the filter and pump manuals before the final shutdown can prevent a small model-specific detail from becoming a spring repair.
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