Getting ready to close your pool for the season? Proper winterization prevents freeze damage, keeps water clean, and makes spring opening a breeze. Whether you DIY or hire a pro, this 5-step guide will walk you through everything you need to close your inground pool correctly.
Step 1: Clean and Test Pool Water
Start with a spotless pool to prevent algae and staining over winter.
The cleaner your pool before closing, the easier it will be to open next spring.
Clean Thoroughly
- Skim all debris from the water surface
- Brush walls, steps, ladders, and corners
- Vacuum the entire pool floor
Use test strips or a liquid test kit to check:
Balanced water prevents corrosion and scaling during the off-season.
Adjust alkalinity first, then fine-tune pH if needed.
Test and Balance Water
- pH: 7.2-7.8
- Alkalinity: 80-120 ppm
Step 2: Drain Pool Below the Skimmer
Lower your water level a few inches below the skimmer to prevent freeze damage.
Don't drain too much — you want water above the main drain but below the skimmer.
How to Drain Using Your Filter System
- Turn off your filter pump
- Set your multiport valve to "backwash"
- Set valves to pull water from the main drain (not the skimmer)
- Turn the pump on and let it run until the sight glass is clear (~2 minutes)
- Turn off the pump
- Set the valve to "waste"
- Turn the pump back on
- Let it drain until water is a few inches below the skimmer
Step 3: Blow Out Pool Lines (Most Important Step)
This step prevents frozen pipes from cracking and causing expensive damage. If you're uncomfortable with this step, hire a professional. Mistakes can cost thousands in repairs.
Equipment You'll Need
- Air compressor, shop vac, or air blower
- Pool plugs for skimmer and return lines
- Teflon tape for threaded plugs
All lines and equipment should now be free of water.
How to Blow Out Lines
- Remove all return fittings and skimmer baskets
- Remove all drain plugs from your filter, pump, heater, and other equipment
- Set multiport valve to "recirculate"
- Set the valve in front of your pump to the skimmer line
- Attach air compressor to the drain opening on your pump
- Turn on the compressor to push air through skimmer and return lines
- Use a shop vac at the skimmer to remove blown-out water until the skimmer is dry
- Plug the skimmer line with a winterizing plug
- Go around and plug all return lines as air pushes water out
- Switch the valve to main drain to blow air that direction (~1 minute)
- Turn valve back to skimmer and shut off air compressor
- Insert a plug inside the pump in case the valve leaks
If you have a heater or fountain, the process is more complex. Consider hiring a professional for tricky plumbing setups.
Special Considerations
Step 4: Add Winter Pool Chemicals
Winter chemicals keep algae away and water clean during the off-season.
Go to your local pool supply store and buy a winter closing kit sized for your pool.
These kits typically include:
Follow kit instructions for dosing based on your pool size.
Broadcast chemicals evenly around the pool with your pump running (if possible), or use a brush to distribute them.
Use a Winter Closing Kit
- Algaecide
- Shock
- Stain and scale preventer
Step 5: Install Your Winter Cover
The final step is covering your pool to keep debris out and prevent algae growth from sunlight.
Safety covers are made of mesh or solid material and are anchored to the deck with straps.
Benefits:
Installation: Stretch the cover over the pool and secure all anchor straps to the deck.
Option 1: Safety Cover
- Keeps people and pets safe
- Drains rainwater (mesh) or sits on top (solid)
- Lasts 10-15 years
Winter tarp covers are large plastic sheets secured with water bags.
Benefits:
Installation:
Don't use bricks or concrete blocks — they can fall through the cover and damage your liner.
Option 2: Winter Tarp Cover
- Much cheaper than safety covers
- Blocks sunlight to prevent algae
- Spread the cover over the pool
- Fill water bags about 3/4 full (not completely — they need room to expand if frozen)
- Place water bags around the perimeter to hold the cover down
Optional: Do You Need an Air Pillow?
Air pillows (aka ice compensators) go under your cover in the center of the pool. Benefits: Recommended for above ground pools. Not necessary for most inground pools, but it doesn't hurt.
- Absorbs ice expansion to protect pool walls
- Prevents cover from sagging in the middle
What to Do Next
Double-check that all drain plugs are removed from your filter, pump, heater, and chlorinator. Water left in equipment can freeze and crack housings. Store drain plugs in your pump basket so you know exactly where they are when you open the pool next spring. Inspect your cover periodically throughout winter to remove excess water, snow, or debris.