How to Protect Your Pump, Filter, and Heater Through Winter

Many spring freeze-damage calls start with water that was left inside a pump, filter, heater, or auxiliary line. The U.S. Geological Survey explains that water expands by roughly 9% as it freezes. A rigid equipment cavity gives that expansion nowhere to go, so even a short freeze can crack a housing, header, or fitting when enough water is trapped.

Closing the pool protects the plumbing and the shell. This guide covers the equipment pad: how to winterize a pool pump and a pool heater the way their manufacturers' manuals describe, plus the filter, the salt cell, and the low points that get missed. If you want the full closing sequence instead, start with our step-by-step guide to winterizing your pool in Maryland and Virginia.

Why Winter Breaks Pool Equipment

The deciding factor is not the season's average temperature. It is whether water remains trapped when a component freezes. That is why a mild DMV winter can still damage an incompletely drained equipment pad.

The places water hides are predictable, and they are the places people forget:

• The pump strainer pot and volute, which may still hold water after the basket looks empty.
• The filter tank, pressure gauge, air-relief assembly, and connected outlet piping.
• A gas heater's header and heat exchanger tubes.
• A heat pump's water-side heat exchanger and its inlet and outlet connections.
• Chlorinators, cleaner booster pumps, spa loops, and water-feature branches that sit outside the main circulation path.

How to Winterize a Pool Pump

An empty strainer basket does not prove the pump is drained. Water sits in the strainer pot and the volute below it. Pentair's WhisperFlo and IntelliFlo3 VSF manuals and Jandy's variable-speed pump manual describe the same core procedure:

1. Cut power at the breaker. Stop the pump at its control, then shut off the circuit breaker. Not the timer, not the automation panel — the breaker.
2. Relieve system pressure. Pentair's IntelliFlo3 guide says to open the filter's air-relief valve and stand clear until the pressure gauge reads 0 psi.
3. Remove both housing drain plugs and let the pump empty. All three manuals show two plugs. Pentair says to store them in the strainer basket; Jandy says to keep the plugs and their O-rings together somewhere safe and reinstall them when the cold season ends.
4. Clean the lid O-ring, and follow your brand on lubricant. The WhisperFlo manual says to keep the lid O-ring clean and well lubricated. Jandy's manual says the opposite for its pumps: no lubricant or sealant on the O-ring, only soapy water.
5. Cover the motor, but never in plastic. Pentair says to cover the motor against severe rain, snow, and ice, but not to wrap it in plastic or other airtight material, and never to cover it while it is running or expected to run. Jandy says to keep the motor covered and dry and warns that plastic creates condensation that can damage the pump.
6. Do not run the pump once it is drained. Both Pentair manuals warn that running a pump dry damages the shaft seal and makes the pump leak.

A variable-speed pump's freeze mode is not a winterization. Pentair's IntelliFlo3 guide says not to rely solely on its Thermal Mode for freeze protection, because that mode responds to the drive's internal temperature, not the air around the pad. Like any freeze-protection feature, it can only help an open pool that still has water to move. Once the pool is closed, the pump should be drained and powered off.

Do you need to bring the pump inside? Pentair's procedure leaves the drained pump in place with the motor covered. Jandy's manual goes a step further and recommends having a qualified technician or electrician disconnect the wiring so the pump can be unplumbed and stored indoors. Disconnecting a hardwired pump is electrical work, so do not unwire one yourself.

If your pump leaked, lost prime, or tripped its breaker during the season, diagnose it before closing while it can still be run. Our guide to pool pump failure warning signs explains what each symptom usually means, and our pool-pump repair team can separate a seal or plumbing problem from a motor or full-pump failure.

How to Winterize a Pool Filter

What winterizing looks like depends entirely on which filter you have.

• Sand: backwash, remove the drain cap, and let the tank empty. Remove or drain accessories such as the pressure gauge as the manual directs.
• DE: backwash, open the tank only after pressure is fully relieved, rinse the grids or module, remove residual DE, and let the tank drain. Pentair's System 3 manual also warns that air purging must use a high-volume blower below 5 psi.
• Cartridge: pull and rinse the elements, let them dry, and store them as the manufacturer specifies. Some manuals call for warm, dry storage away from direct sunlight.

The multiport valve. If you have seen a WINTERIZE label on your equipment, check where it is. On a sand or DE filter it is a position on the multiport valve, not a pump setting: the valve's off-season parking spot. Pentair's Hi-Flow top-mount valve manual says to drain the pump and filter first, then turn the handle to the area marked WINTERIZE and leave it there all winter so the diverter puts no pressure on the rubber seal. Hayward's VariFlo valve manual defines its winterizing position as the handle parked between any two settings, which lets the valve drain. Follow the manual for the valve you actually have.

Leave the tank able to drain. If the tank is cracked or the filter was undersized all season, planning the replacement now avoids a spring scramble. Our pool filter replacement cost guide covers the ranges by type.

How to Winterize a Pool Heater

Heaters are among the most expensive components on the pad, and neither a gas heater nor a heat pump is freeze protection. Pentair's MasterTemp gas-heater manual says to shut the heater down and winterize it when air temperatures are expected to drop below 32°F. Hayward's Universal H-Series service and installation manual says not to use the heater to hold water just above freezing, and to drain all water from it when it is out of service in a freezing climate. Both manufacturers exclude freeze damage from the warranty.

Gas Heaters

1. Shut it down completely. Turn off electrical power to the heater and the pump, switch the heater's gas valve to OFF, and close the manual gas shutoff outside the cabinet. Hayward's procedure starts by putting the heater in STANDBY.
2. Check where the heater sits. If it is below the pool's water level, opening the drain will start draining the pool. MasterTemp says to close the isolation valves first; Hayward says to isolate the heater with valves or partially drain the pool.
3. Open the drain. On a MasterTemp, that is the drain cock on the bottom of the manifold adapter. On an H-Series, it is the plastic drain plug on a plastic header or the brass drain valve on a bronze (ASME) header.
4. Clear what gravity misses. MasterTemp calls for blowing out the heat exchanger through the pressure-switch fitting with a high-volume blower below 5 psi, then removing the water pressure switch, plugging its port, and draining the inlet/outlet manifold through the outlet pipe. The manual warns that purging with compressed air can make components explode, which is why it caps the pressure.
5. Keep debris out. MasterTemp says to cover the air-inlet grate with a plastic bag to keep bugs and leaves out. That is a grate cover, not a wrap for the whole cabinet.

The manuals differ on the drain afterward. MasterTemp's return-to-service step is to close the drain cock, so it stays open over winter; Hayward's procedure reinstalls the plug once the water is out. That difference is why the exact model's manual matters. A visibly empty header does not prove every exchanger tube is clear, and a cracked exchanger runs $800 to $1,800.

Heat Pumps

A heat pump's cabinet is built to sit outdoors; it is the water side that freezes. Pentair's UltraTemp heat-pump guide says to turn off power at the main breaker, shut off the water supply, and disconnect the inlet and outlet unions on both sides of the unit so all the water can drain freely. Then cover only the top to keep debris from falling in. Do not wrap the sides in plastic or anything else that holds heat or moisture inside the unit.

Restarting the Heater in Spring

Never fire a heater into a dry or half-filled system. MasterTemp says not to turn the heater on until water is circulating, then to run water through it for several minutes until the air noises stop. Hayward says to confirm the drain valve is closed and run the pump long enough to purge the air before turning the gas back on. UltraTemp says to reconnect the unions, bleed the air, and check for leaks before restoring power at the breaker.

Whatever the type, check the heater for nesting before startup. A dormant gas heater is a warm, sheltered box, and rodents find it. Nesting material against the burner tray is a spring hazard, not just a mess.

If your heater struggled all season, diagnose it before shutdown while it can still be run through a full heat cycle. Our guide to pool heater repair vs. replacement costs walks through which findings are worth fixing, and our pool heater repair team services both gas heaters and heat pumps.

Salt Cells, Chlorinators, and Automation

• Salt cell: follow the generator manual. Pentair's current IntelliChlor guidance, for example, says to drain the plumbing, remove the cell, and install a spacer cell. Hayward's AquaRite manual says freezing water damages the cell just as it does the plumbing. Both generators also shut off in cold water (below 50°F for AquaRite, about 52°F for IntelliChlor), so the cell has no job to do in a closed pool. Inspect the plates and clean only if scale is visible: an installed replacement cell runs $1,800 to $2,500, and every needless acid wash spends cell life. Our saltwater end-of-season checklist covers the rest of the system.
• Tab chlorinator: with the system off and depressurized, remove remaining tablets and drain the feeder according to its manual and the chemical label. Concentrated chlorinated water left stagnant can corrode the feeder and downstream equipment.
• Automation: the freeze-protection feature does not help a closed pool. Freeze protection works by circulating water, and there is no water in the lines to circulate. Power the system down per the manufacturer's guidance, keep the controller enclosure dry and closed, and do not rely on it as a safety net.
• Auxiliary systems: drain cleaner booster pumps and clear water-side spa, water-feature, and solar-heating branches according to their own layouts. Do not assume the main-filter blowout emptied them.

What It Costs When It Goes Wrong

The reason this job is worth doing carefully is the size of the gap between prevention and repair:

Freeze casualty	What it costs to fix
Pump repair or motor rebuild	$300 – $600
Pump replacement (single-speed / variable-speed)	$1,000 – $1,800 / $1,800 – $3,200
Filter replacement (cartridge / sand / DE)	$900 – $2,800 / $1,200 – $2,800 / $1,500 – $3,200
Heat exchanger replacement	$800 – $1,800
New heater installed (gas or heat pump)	$5,000 – $10,000
Salt cell replacement (installed)	$1,800 – $2,500

A professional closing is a flat $500 with chemicals included. Set against a cracked heat exchanger or a new pump, the arithmetic is not close.

Do Not Assume It Is Fine Until April

The DMV's freeze-thaw pattern makes mid-winter checks worth doing. Rain and snowmelt can change water levels and cover tension before the next freeze. A closed pool is not a sealed system, and months can pass before a moved cover or refilled low point is otherwise discovered.

A short walk-around once a month covers it: confirm the drain openings remain clear, check that the cover is tensioned and not holding a pond, look for standing water around the pad, and inspect the heater for nesting. Our guide to pool maintenance after closing covers those checks in more detail. If you would rather not do it yourself, our winter service visits start at $180 and include chemistry under the cover, an equipment check for freeze issues, and cover-strap re-tensioning.

If something already looks wrong—a missing plug, cracked housing, or water where the manual says the component should be dry—our guide to troubleshooting common pool equipment problems will help you identify it. Handle the diagnosis before opening season if possible.

The Short Version

Power off at the breaker, relieve pressure, remove every drain plug named in the equipment manuals, and make sure the pump, filter, heater, chlorinator, and auxiliary water circuits can drain. Park the multiport valve where its manual says, disconnect a heat pump's unions, and store removable cells, filter elements, plugs, and O-rings as their manufacturers direct. Cover a pump motor or the top of a heat pump if the manual allows, but never wrap a heater or motor in plastic. Then check the pad and cover once a month through winter.

Beltway Pools closes and winterizes inground pools across Northern Virginia, Montgomery County, and Washington, DC for a flat $500 with chemicals included. Winter Watch visits start at $180 if you want the water, equipment pad, and cover checked while the pool is closed. Book a professional pool closing, see what our repair team handles if something is already damaged, or request a quote.