In many regions’s climate, seasonal opening and closing are the two most consequential pool service events of the year. A proper closing protects the pool and all its equipment through months of freeze-thaw cycling. A proper opening sets up the chemistry and equipment for a trouble-free swimming season. Both are more involved than most homeowners realize — and shortcuts in either create expensive problems.
“The closing is where I see the most preventable damage. Lines that weren’t blown out properly. A heater that wasn’t drained completely. An expansion plug that wasn’t seated correctly. Water freezes at 0 degrees Celsius, and it expands with enough force to crack PVC fittings and split heat exchangers. A thorough closing takes 2–3 hours and prevents repairs that can cost $500 to $5,000. There’s no shortcut worth taking.”
— Adam, pool service specialist at Clark Pools in Owen Sound, with 15 years of experience in residential pool installation, service, and renovation in the local area, as seen on Netflix’s Hotel Makeover
Table of Contents
Questions About Seasonal Closing
What does the closing service include?
A thorough professional pool closing in many regions should include:
Water chemistry pre-treatment:
– Balancing pH, alkalinity, and calcium hardness to ideal ranges before closing (balanced water protects the liner/surface through winter better than imbalanced water)
– Adding a winterizing algaecide (non-copper based is generally preferred)
– Adding a phosphate remover if phosphate levels are elevated
– Adding a stain and scale preventer
– Shocking the pool to ensure adequate sanitizer going into winter
Equipment removal and storage:
– Removing and storing all ladders, rails, and removable fittings
– Removing and storing the pump strainer basket and filter cartridges (for cartridge filters)
– Removing all return fittings and skimmer baskets
Blowing out all plumbing lines:
Using a commercial air compressor to blow all water out of the plumbing lines — return lines, skimmer lines, main drain lines. This is the most critical step. Any water remaining in the lines can freeze, expand, and crack fittings and pipes.
Antifreeze (in some cases):
After blowing out the lines, some technicians add pool-grade (propylene glycol) antifreeze to the skimmer lines as an additional freeze protection measure. Ask whether this is included or recommended for your pool’s configuration.
Expansion plugs:
Installing expansion plugs in all return fittings, skimmer openings, and any other plumbing openings to prevent water intrusion.
Equipment winterization:
– Draining and winterizing the pump
– Draining and winterizing the heater — specifically, ensuring the heat exchanger is fully drained
– Draining and winterizing the filter
– Disconnecting and storing the salt cell (for saltwater pools)
Water level adjustment:
For most pools, water level is dropped slightly below the skimmer opening(s) to prevent ice damage to the skimmer.
Winter cover installation:
Installing the winter cover and securing it to prevent wind from lifting it and debris from entering the pool.
Ask for a written checklist of everything included in the closing service.
Will all plumbing lines be blown out with a compressor?
Ask this specifically and confirm it’s included. This is the step that prevents the most expensive freeze damage. A company that closes pools by draining water level and adding antifreeze but not blowing lines is leaving water in the plumbing.
Will the heater be properly drained?
The heat exchanger in a gas or electric heater must be completely drained before freezing temperatures. Residual water in the heat exchanger can crack or destroy it — a repair or replacement that costs $500–$3,000+. Ask specifically how the heater is winterized and whether it will be confirmed fully drained.
Questions About Seasonal Opening
What does the opening service include?
A professional pool opening in many regions should include:
Cover removal and storage:
– Removing the winter cover carefully (pumping any accumulated water off a solid cover first)
– Cleaning the cover before folding and storing it
– Inspecting the cover for damage
Equipment reinstallation:
– Reinstalling the pump, filter, heater, and other equipment removed or stored for winter
– Reconnecting all plumbing connections
– Reinstalling return fittings and skimmer baskets
– Reinstalling ladders, rails, and handrails
System startup:
– Priming and starting the pump
– Running the filter and checking for leaks
– Starting the heater and verifying proper operation
– Starting the automation system (if applicable)
Water level:
Filling the pool to the correct operating water level if it was lowered for winter.
Opening water treatment:
– Comprehensive water testing (all parameters)
– Adding all required chemicals to balance the water — pH, alkalinity, calcium hardness, stabilizer, sanitizer
– Shocking the pool to establish a sanitizer residual
– Adding opening algaecide
Inspection:
– Visual inspection of the liner or pool surface for any winter damage
– Inspection of all equipment for any damage or wear that occurred over winter
What is the timeline from opening to swimmable water?
After opening treatment, the pool typically requires 24–48 hours of filtration and chemistry stabilization before it’s safe and comfortable to swim in. Ask what the expected timeline is for your pool type and what the finishing chemistry levels should be before swimming.
Questions About Timing
When is the best time to open and close my pool in many regions?
Opening: In many regions, most pools are opened in mid-May. Opening too early (water below 15°C) provides conditions where some algaecides are less effective and where the investment in opening chemicals is higher. Opening too late means the pool is susceptible to algae growth in warm spring water with no sanitizer present.
Closing: In many regions, most pools are closed in late September to early October. Closing when water temperature is consistently below 15°C reduces the risk of algae developing during the closing process, when sanitizer is being removed from the water. Never close a pool that already has algae — treat the algae first, then close.
Ask the company when they recommend opening and closing for your specific location and pool configuration.
Related Questions
- Questions to Ask a Pool Service Company Before You Hire One
- Questions to Ask a Pool Service Company About Water Chemistry
- How Much Does Pool Service Cost ?
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