What chemicals do you need to add when closing up a pool?(Canada)

I’m using a new pool company this year to close up my pool for the winter. They have great reviews and don’t add anything to the water themselves—they said they’ll use whatever I provide. Other companies used to charge for “winterizing chemicals” but never explained what they were. So, what should I be providing, if anything? My pool is about 20 x 40 feet (around 120,000 liters or 31,700 gallons), and I’m in Manitoba where it can get down to -30°C. Thanks for any advice!

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The LSI of the water should be adjusted for the coldest temperature expected. If this is planned and accounted for properly, you might not need to make significant changes.

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@AquaAdventurer I also prefer using a long-lasting copper algaecide because most people don’t open their pools on schedule.

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@BreaststrokeBuff I don’t do that. I’d rather handle a green pool if a client opens late than deal with the copper later.

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Ensure the water is fully balanced -always is anyways, then drain the water down to expose my lowest jets (step jets); add some liquid chlorine (I run a salt pool but pickup some liquid when closing), and some algicide; blow the lines out, then blow some pool antifreeze through and cap the lines; and put on the safety cover.

Had my pool for 20 years, last two years I paid a company to do the closing. Maybe I’ll do it myself this year.

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Really nothing. Water must be in equilibrium. When I open it, it generally looks a little green because of the mesh cover.

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I manage a pool company and add 5 lbs of calcium hypochlorite shock and 1 quart of Algaecide 60 to each pool before closing. I perform this treatment on the same day as closing, right before I blow out the lines and cover the pool. I suggest you follow this approach.