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When Should You Close Your Pool?

One of the most common questions that we get from pool owners is “when should we close our pool?”. Once September hits most pools don’t get used too much as temperatures begin to drop and kids ago back to school.

For many pool owners, the temptation is to close the pool as soon as it’s not being used so that they no longer have to pay to run it. Today, we will explore why that is not always the best choice and give you the tools you need to decide when the best time to close your pool is.

Why Not Close Your Pool Early?

While the temptation to close your pool early to save on the maintenance and running costs is understandable, closing your pool too early can in fact end up costing you more in the long term than leaving it open!

The danger with closing your pool too early is that the chlorine in the water will run out too quickly. Without chlorine in the water, algae will start to grow; causing green or even black water in the spring. Not only does this look bad, it can take a lot of time, effort and expense to clear once the pool is open.

Factors That Change When You Should Close Your Pool

Knowing exactly when you should close your pool can be tricky since there’s no set “ideal” pool closing date. In fact, there are a variety of factors that can change when you should close your pool. Here are the most important of those factors.


The biggest factor that affects when you should close your pool is the temperature of the pool water. The higher the water temperature is the faster the chlorine residual in the water is used up. Once the chlorine in the pool water is spent, algae will begin to grow.

If you close your pool while the temperature of the water is too high the chlorine in the pool water won’t last until spring. Algae growth begins to slow at around 65 degrees Fahrenheit but doesn’t completely stop until the water reaches around 40 degrees Fahrenheit. Simply put, closing your pool when the water is above 65 degrees is a recipe for disaster in the spring.


As long as the pool is getting used, it is probably worth keeping open. If your pool has a heater you can easily maintain a comfortable swimming temperature even as temperatures outside begin to drop; extending your swimming season for at least a few weeks.


The main reason that people have for closing their pools early is the cost of maintaining their pool for an extra couple of months after it is no longer being used.

Fortunately, the costs of running your pool in the fall is significantly less than it is in the summer. There are two reasons for this:

  • Cold water goes through much less chlorine than warm water. To maintain a good chlorine residual in the fall will likely only require 1-2 pucks per week. You will also only need to shock the water every 2-3 weeks.
  • The water doesn’t need to circulate as long in the fall. In the heat of the summer you should be leaving your pool pump running for at least 12 hours per day to maintain clear water. Once the water cools down and isn’t being used nearly as much, however, you can get away with only running the pump for 4-6 hours per day.

While keeping your pool open for weeks or even months after it isn’t being used may seem like a waste of money, the costs of clearing a green pool in the spring can easily exceed these costs.

Tree Cover

If you have a lot of trees around your pool you may want to consider closing the pool before the leaves start to fall, even if the water isn’t quite cold enough yet. Not only is removing all those leaves a big job, they also cause you to go through much more chlorine than you normally would. If left in the pool over the winter, they can also cause staining on the pool surface that can be difficult and expensive to get rid of.

The exception to this rule would be if your pool has a safety cover. Since safety covers can be installed fairly easily without closing the pool, you can install your safety cover when the leaves start falling. The leaves will simply land on the cover and blow away in the wind. Once you’re ready to close you take the safety cover off, close the pool normally and put it back on.

Wrapping Up

So when should you close your pool? As late as you can. The later that you close your pool the easier it will be to open and the less time and money you will have to spend fixing potential water quality issues. Although this will cost you a little more in the fall to run your pump and treat the water, these costs are almost always less than the costs of fixing green water in the spring.

At a minimum you will want to wait until the water constantly stays below 65 degrees Fahrenheit; even in the middle of the day. For best results, wait until the water is consistently below 50 degrees Fahrenheit.

Read More: Pool Closing Tips


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