Oásis Biosistema

How to Drain Pool Equipment: Complete Pump, Filter, and Heater Guide

Draining pool equipment removes water from pump housing (remove 2 drain plugs on volute bottom), filter tank (open air relief valve and bottom drain plug, set multiport valve between positions for sand filters), heater (remove drain plugs from heat exchanger header after 15-minute cool-down), and inline chlorinators or salt cells before freezing temperatures cause water expansion damage costing €300-800 per pump, €400-1,200 per filter, and €600-2,000 per heater. Equipment draining takes 15-30 minutes total and is required for winterisation in freezing climates, required before equipment transport or storage, and necessary before any electrical or plumbing repair work on pool systems.

This guide covers equipment-specific drain plug locations, sand filter multiport valve positioning, cartridge and DE filter drainage procedures, heater drain procedures by common models, salt cell removal, air compressor line blowing after equipment drainage, drain plug storage to prevent loss, and o-ring lubrication before storage.

Key Takeaways

  • Pump: 2 drain plugs on housing bottom – one inlet side, one outlet side of volute

  • Sand filter: multiport valve between settings – allows air into tank, accelerates drainage

  • Cartridge/DE filter: remove cartridge or grids – clean and store separately, leave tank open

  • Heater: allow 15-minute cool-down – hot heat exchanger can warp if cold water contacts immediately

  • Store all plugs in pump basket – single location, found easily at spring start-up

  • Lubricate all o-rings – pool-grade silicone or Teflon lubricant prevents cold cracking

  • Blow lines after equipment drainage – air compressor clears plumbing, equipment drainage alone insufficient

  • Portugal mild climate – coastal areas rarely require full equipment drainage

When Equipment Drainage Is Required

Freeze Protection

Water expands 9% on freezing: Any water remaining in equipment housings or plumbing generates internal pressure exceeding equipment tolerances. Pump housings crack, filter tanks split, heat exchanger tubes burst.

Temperature threshold: Drain equipment when sustained air temperatures below 0°C (32°F) forecast. Equipment in shaded, exposed, or elevated locations freeze faster than ambient temperature suggests.

Portugal context: Coastal Portugal (Lisbon, Porto, Algarve) rarely reaches sustained freezing. Interior and northern mountainous regions (Trás-os-Montes, Serra da Estrela) can experience sustained freezing requiring full equipment drainage.

Equipment Transport and Storage

Remove and drain all equipment before transporting to storage or off-site repair. Water in transit freezes in cold vehicles, spills during handling, and adds unnecessary weight.

Repair and Maintenance Work

Drain relevant equipment before opening unions, replacing fittings, or performing electrical work on pump motors. Reduces spillage during disassembly and eliminates water contact with electrical components.

Step 1: Turn Off All Power

Circuit breaker: Switch off dedicated pool equipment breaker at consumer unit before touching any equipment.

Automation system: Set pool automation controller to Service or Off mode. Prevents automated pump start during drainage procedure.

Verify power off: Attempt to start pump at controller and make sure to confirm no response before proceeding.

Step 2: Close Isolation Valves

Close all valves isolating pool equipment from pool water (skimmer valve, main drain valve, return valves). Prevents pool water draining back through equipment when plugs are removed.

If no valves present: Lower pool water level below return jets and skimmer opening before draining equipment. It prevents pool water gravity-feeding through equipment.

Step 3: Drain the Pool Pump

Locating Drain Plugs

Standard pump layout: Two drain plugs on underside of pump volute (housing) with one on inlet (suction) side, one on outlet (pressure) side. Plugs typically 19-25 mm diameter, threaded plastic or brass.

Common pump brands:

Hayward: Two 19 mm drain plugs on underside of strainer pot (lower housing). May also have additional plugs on the volute body depending on model.

Pentair: Two plugs on volute underside. WhisperFlo and SuperFlo models have plugs accessible from the front of the pump.

Jandy/Zodiac: Two plugs on the pump body. Some models have inspection windows – plugs adjacent to window seam.

If plugs are not visible: Consult pump manual. Plugs are sometimes located inside the strainer pot cavity (remove lid and basket first) or on the side of the volute near union connections.

Drainage Procedure

  1. Remove pump strainer lid (large threaded lid on top of pot)
  2. Remove strainer basket, set aside
  3. Remove both drain plugs from pump volute underside – water drains from housing
  4. Tilt pump gently side-to-side to drain water from internal impeller chamber – water in impeller housing does not drain by gravity alone
  5. Leave both drain plugs out through winter (allows condensation to escape, confirms plugs not forgotten)
  6. Place both plugs inside strainer basket and they will be there at spring start-up

Disconnect unions (optional for thorough draining): If pump has threaded unions on inlet and outlet, disconnect union collars and tip the entire pump unit to drain thoroughly. Useful for pumps installed below pool water level where backflow risk is higher.

Lubrication

Apply thin coat of pool-grade silicone or Teflon-based lubricant to:

  • Strainer lid o-ring (flat rubber ring on underside of lid)
  • Both union o-rings (if unions disconnected)

Lubrication prevents rubber drying and cracking during winter storage. Do not use petroleum-based lubricants (Vaseline, WD-40) as they degrade rubber o-rings.

Step 4: Drain the Filter

Sand Filter Drainage

Multiport valve positioning: Set multiport valve handle between two positions (e.g., between Backwash and Rinse, or between Filter and Closed). Lifting handle off detent positions allows air into the tank through the valve body, accelerating drainage. Some manufacturers specify a “Winterise” position if present on the valve.

Air relief valve: Open the small air relief valve on top of the filter tank (knob or lever). Air enters from top as water drains from bottom and it speeds drainage from hours to minutes.

Bottom drain plug: Located on the underside of the filter tank. Remove completely. Water drains.

Leave it open all winter: Keep the air relief valve open and drain plug removed. Plug stored in pump basket.

Backwash before closing: Backwash filter before final drainage. It removes trapped debris from the sand bed that would decompose over winter.

Sight glass: Remove pressure gauge and sight glass from multiport valve if equipped. They both contain water and glass components that crack in freezing conditions. Store indoors.

Cartridge Filter Drainage

  1. Open air relief valve on tank top
  2. Remove drain plug from tank bottom
  3. Open tank (unscrew clamp band or twist-lock collar)
  4. Remove cartridge(s) from tank
  5. Rinse cartridge with hose – remove trapped debris
  6. Soak in cartridge cleaning solution overnight if seasonal cleaning scheduled (remove oils, mineral deposits, algae)
  7. Rinse thoroughly after soaking, allow to dry completely (2-3 days minimum in ventilated area)
  8. Store dried cartridges in dry indoor location or reinstall loosely in tank with drain plug removed and lid ajar
  9. Lubricate tank o-ring with silicone lubricant before closing

Inspect during removal: Check cartridge for torn pleats, collapsed core, embedded debris that cleaning cannot remove. Replace if damaged – installing degraded cartridge at spring start-up reduces filtration efficiency from first use.

DE (Diatomaceous Earth) Filter Drainage

  1. Backwash filter – removes old DE coating from grids
  2. Open tank (unscrew clamp band)
  3. Open air relief valve
  4. Remove drain plug from tank bottom
  5. Remove grid assembly from tank – lift complete manifold with attached grids
  6. Rinse each grid individually with hose, removing all DE residue and trapped debris
  7. Inspect grid fabric for tears (any breach allows DE to pass into pool water on restart)
  8. Allow grids to dry completely before storage or reinstallation
  9. Store grids in tank (with drain plug removed, lid ajar for ventilation) or dry indoor location
  10. Do not pre-load new DE before winter – load at spring start-up only

Step 5: Drain the Heater

Safety First

Cool-down period required: If heater ran recently, heat exchanger internal temperature can reach 60-80°C. Removing plugs immediately allows residual hot water to flash-cool metal components rapidly. It can cause thermal stress cracking in heat exchangers. Wait 15-20 minutes minimum after last heater operation.

Gas supply: Turn off gas supply valve on gas line to heater before any work.

Electrical supply: Circuit breaker off in addition to gas.

Drain Plug Locations by Heater Type

Pentair MasterTemp / Sta-Rite Max-E-Therm: Two plugs on front header (horizontal pipe across front of unit at base where water enters/exits). Remove both. Older models may have additional plug on rear header and you can access it through side panel removal.

Hayward H-Series: Two plugs on inlet/outlet header at base of unit. Hayward recommends also disconnecting unions to allow complete drainage from union bodies.

Raypak: Single or double plugs on front header. The ProTek Shield module (on newer models) unscrews entirely from the header providing drainage access. Store modules indoors.

Jandy/Zodiac LXi: Plugs on header front. Consult specific model documentation as header design varies between generations.

Drainage Procedure

  1. Remove drain plug(s) from heat exchanger header
  2. Open pressure relief valve if equipped – allows air into heater as water exits
  3. Tilt heater toward drain side if access allows – removes more residual water from heat exchanger passages
  4. Store drain plugs in pump basket
  5. Cover exhaust vent opening with wire mesh or aluminium screen secured with cable ties – prevents rodents nesting in heater interior over winter
  6. Leave side panels in place or remove per manufacturer recommendation (varies – consult manual)

Step 6: Drain Chlorinator and Salt Cell

Inline Tablet Chlorinator

  1. Remove lid from chlorinator body
  2. Remove all remaining chlorine tablets – undissolved tablets in sealed chlorinator create concentrated acid solution over winter causing internal corrosion
  3. Rinse interior thoroughly with hose
  4. Remove drain plug if equipped
  5. Leave lid loosely seated allowing ventilation and drainage

Salt Chlorine Generator Cell

Remove entirely before freezing: Salt cells must be removed as water inside cell housing expands when frozen, cracking electrode plates (€300-800 replacement cost).

  1. Turn off salt system power at controller and circuit breaker
  2. Unscrew union connections at cell inlet and outlet (hand tight or strap wrench)
  3. Remove cell from plumbing
  4. Inspect electrode plates for calcium scale buildup – white or grey deposits
  5. Clean scale: light deposits rinse with hose; moderate deposits scrape gently with plastic tool; heavy deposits soak in 1:10 diluted muriatic acid for 15-30 minutes, rinse thoroughly with fresh water
  6. Dry cell completely (24 hours minimum)
  7. Store indoors in climate-controlled location – garage, utility room, inside house
  8. Install dummy cell (non-functional spacer) in plumbing to maintain sealed loop; alternatively cap unions with threaded caps

Step 7: Blow Out Plumbing Lines

Equipment drainage alone is insufficient: Draining equipment removes water from equipment housings but leaves water in underground plumbing lines (return pipes, suction lines) between equipment pad and pool. Underground pipes are the most expensive to repair if frozen (€1,000-3,000 excavation plus pipe replacement).

Procedure

Equipment: Air compressor, 5-20 PSI. Shop vacuum in blower mode as an alternative for smaller pools.

Return lines (equipment to pool):

  1. Connect air compressor to return line at equipment pad
  2. Increase pressure gradually to 15-20 PSI
  3. Watch pool return jets – blow until steady continuous bubbles emerge
  4. Maintain air flow 2-3 minutes after bubbles visible
  5. Install winter plug in return jet immediately while air flowing – maintains air lock preventing water refilling line

Suction lines (pool to equipment):

  1. Connect air to skimmer line
  2. Blow until bubbles emerge from skimmer in pool
  3. Install gizzmo (skimmer guard) in skimmer – absorbs ice expansion protecting skimmer body from cracking

Never exceed 20 PSI: Higher pressure can blow out fittings, crack PVC pipes, damage unions.

Pool Antifreeze (Optional)

Non-toxic propylene glycol antifreeze poured into skimmer and return lines after blowing provides backup protection if any water remains. Use pool-specific antifreeze only. Never use automotive antifreeze (ethylene glycol, toxic to plants and animals).

Dosage: 1 litre per 10 linear metres of plumbing. Available from pool supply retailers.

Drain Plug Organisation

All plugs in pump basket: Standard practice: pump (2 plugs), filter (1 plug), heater (1-2 plugs), chlorinator (1 plug) stored in pump strainer basket. Single location, found immediately at spring start-up without searching.

Label if needed: Multiple equipment items or complex systems may warrant labelling plugs with masking tape and permanent marker indicating origin (Pump Inlet, Filter Base, Heater Front).

Count at start and finish: Before beginning, count expected total plugs. Verify the same number in the basket at completion. Missing plug means water still in equipment.

Spring Reinstallation Checklist

  1. Reinstall all drain plugs in correct equipment (hand tight plus quarter turn – do not overtighten)
  2. Reinstall salt cell (reconnect unions, hand tight, check for leaks on first start)
  3. Reinstall pressure gauge and sight glass in filter
  4. Close filter air relief valve
  5. Reopen all isolation valves
  6. Fill pump strainer basket with water before replacing lid (primes pump)
  7. Restore power at circuit breaker
  8. Start pump, check for leaks at all unions and drain plug locations
  9. Check filter pressure (normal operating range 1-2 bar)
  10. Restore salt system operation, verify salt level, recalibrate cell output

Natural Pool Equipment Drainage

Natural swimming pools use simpler equipment configurations than conventional pools, reducing winter drainage requirements.

No heater typically: Most natural swimming pools in Portugal operate without heaters as the mild Mediterranean climate extends the swimming season without supplemental heating, eliminating heater drainage from winter procedure.

No salt cell or chlorinator: Biological filtration through planted regeneration zones replaces chemical sanitisers entirely. No salt cell, no chlorinator, no associated drainage steps.

Simplified pump drainage: Single circulation pump (or two at most for dual-zone systems) requires standard pump drain plug removal. It’s the same procedure as conventional pools but fewer items total.

Reduced plumbing complexity: Natural pool plumbing circuits simpler than conventional pools without chemical dosing infrastructure, reducing number of line-blowing steps at winterisation.

Oásis Biosistema designs natural swimming pools with simplified equipment configurations eliminating heaters, salt systems, and chemical dosing equipment from winterisation procedures, reducing equipment drainage steps to pump and filter only while biological filtration through planted regeneration zones maintains water quality without the chemical equipment requiring additional seasonal maintenance.

Conclusion

Draining pool equipment requires removing pump volute drain plugs (2 per pump, tilt unit to drain impeller chamber), setting sand filter multiport valve between positions with air relief and bottom drain plug open, removing and cleaning cartridge or DE filter elements before storage, waiting 15-20 minutes before removing heater header drain plugs, extracting and storing salt cells indoors after acid cleaning scale deposits, and storing all plugs in pump strainer basket for spring retrieval.

Equipment drainage alone does not protect plumbing. Blow out all underground lines with air compressor at maximum 15-20 PSI installing winter plugs in return jets immediately while air flows to maintain air locks preventing refill.

Natural swimming pools designed by Oásis Biosistema simplify winter equipment procedures by eliminating heaters, salt cells, and chemical dosing systems through biological filtration in planted regeneration zones, reducing seasonal drainage to pump and filter only in chemical-free Portuguese pool installations.

FAQ

How do I drain my pool equipment?

To drain pool equipment, turn off the power, open the drain plugs on the pump, filter, heater, and chlorinator, and allow all water to flow out. This is an important step when winterizing a pool to prevent freeze damage and extend equipment life.

Should I drain my pool equipment?

Yes, if your area experiences freezing temperatures. Draining water from pumps, filters, heaters, and plumbing helps prevent cracking and costly repairs. In warm climates where freezing is not a concern, complete equipment draining is usually unnecessary.

How do I drain a pool without fancy equipment?

You can drain a pool using a garden hose and the siphon method. Place one end of the hose in the pool, fill it with water, then place the other end at a lower elevation outside the pool to start the flow.

How do I manually drain water from a pool?

The simplest manual method is siphoning with a hose. For small amounts of water, you can also use buckets or a submersible utility pump. Always discharge water according to local regulations and avoid draining a pool too quickly.

To drain pool equipment, turn off the power, open the drain plugs on the pump, filter, heater, and chlorinator, and allow all water to flow out. This is an important step when winterizing a pool to prevent freeze damage and extend equipment life.

Yes, if your area experiences freezing temperatures. Draining water from pumps, filters, heaters, and plumbing helps prevent cracking and costly repairs. In warm climates where freezing is not a concern, complete equipment draining is usually unnecessary.

You can drain a pool using a garden hose and the siphon method. Place one end of the hose in the pool, fill it with water, then place the other end at a lower elevation outside the pool to start the flow.

The simplest manual method is siphoning with a hose. For small amounts of water, you can also use buckets or a submersible utility pump. Always discharge water according to local regulations and avoid draining a pool too quickly.