How To Keep a Swimming Pool Clear Year Round

A Santa hat floating on water.

At the beginning of every swimming season when I remove the cover from my pool, there is usually someone that acts amazed at how clear my pool is.  They will typically ask how I keep my pool clear throughout the winter?

Most people assume at the start of each swimming season there is a waiting period of 1 or more weeks required before the pool is ready for swimmers to enter the water.

This is actually true, but not for the reason most people think. When I open my pool, you will likely wait several weeks before entering the water, however there will be little work I have to do to get it sanitized and ready for opening day.

The most important thing you can do to keep your swimming pool clear year round is sanitizing the water.  Be sure you never cover your pool to early or late in the season.  When the water is above 65 degrees, you should continue adding chlorine regularly as well as running your pool pump on a daily basis.


The water is freezing cold, lets close the pool up.  This is one of the biggest mistakes made by pool owners and I am not innocent.  When I first became a pool owner me and the entire family was excited.  We swam more the first season than any other season since we purchased it.

Once September arrived and cool air took over the region we stopped swimming.  I then decided it was time to order myself a pool cover.  I got a really good deal from and because I only paid about $30 for it I didn’t think it would last more than 1 season or 2 at best.  To my surprise it has lasted now 4 years and it will be used again at the end of this season.

The tarp arrived, it is a black tarp and you can see it in one of my other posts that revolves around the same idea called – What is the best time to open your swimming pool?

As soon as the it arrived in the mail, the family and I placed the cover over the pool.  We tightened it up with the attached strap it came with and added a few extra clamps to prevent the winter winds from possibly ripping it.  That could also be partly why it has lasted so long considering the strong north winds we receive in Oklahoma during the wintry months.


While it is true we were no longer swimming in the pool, it isn’t true that it was time to officially close the pool for the season.

Closing the pool is a term that many think of as shutting it down once too cool to swim or postponing all maintenance until next spring or early summer.  When it is thought of like this, trouble is surely to find its way into your pool waters.


When we placed the cover on the pool and left it to sit for months, the water was still warm enough for algae and other bacteria to grow inside the pool.  When you leave these right kind of conditions for this growth, there is no doubt your pool will not remain clear over the winter months.  It may even become completely disgusting as ours did.

When we closed our pool in early September the water temperature was likely still in the upper 60’s for several weeks if not a full month.  This allowed bacteria growth up to the time in which live algae could no longer survive.

This also remained in the water over the course of the winter.


Just as the water temperature was well above 65 degrees in early September, the water will once again rise above 65 degrees well before May or the beginning of your swimming season.  This can however vary, based on your location or how cold your winter was during the off season.

Lets say the water of your swimming pool reaches above 65 degrees on average in mid April.  The algae that is already in your pool from the winter months is about to get some more company.  You could potentially have another 1 or more months of algae that will start to grow and infest your pool prior to opening season.

When it is time to remove the cover and jump in, you are going to find a green, non-clear water underneath and you will have to spend days or even weeks restoring your pool back to crystal clear water.

On top of the time and energy it is going to take to restore you pool, the money on chemicals is going to cost more as well. 

You will need a large dose of algaecide, high levels of chlorine shock and stabilizer to help bring your pool back.  A cheap and effective way to get this started is by purchasing bleach as your chlorine agent rather than spending large sums for chlorine at your local pool stores.

Once of the best ways to prevent this from happening is simply not covering your pool until the average temperature of your pool is 65 or below.  During this time you will want to also continue to add chlorine to prevent any algae from occurring.


This is a no-brainer during the summer months when kids and adult take to the pool on a regular basis.  It however is often overlooked and forgotten during the non-swimming months.

No matter what your chlorinating agent is, it is necessary to remain consistent even during the times the weather has made it too chilly to take a dip.


During the cooler months when people are staying indoors more, or the family barbecue is a cookout and croquet instead of a pool party, less chlorine is usually required.

  • If you are using chlorine tablets to maintain your pools proper chlorine levels, when the water is cooler the tablets will dissolve at a slower rate.  Also since there are no swimmers in the pool, there will be less chlorination necessary to maintain the cleanliness of the water.
  • For those that add bleach on a daily basis, simply continue adding bleach as you do every day.  The amount of bleach you will need to add will be less as the water temperature decreases.  This is because less of the chlorine will burn off on cooler days.
  • Salt chlorination pools really have little change required.  You will likely however be able to cut back the amount of time your salt chlorinator is running, thus saving on electricity during this time.

Additionally, if you typically shock your swimming pool once per week, it is a good idea to keep this routine, although you could cut back to shocking it only about twice per month during the off season.

It is important to maintain chlorine in your water during the months when the water is too cold to swim, but remains above the 65 degree mark.  Depending on your method of maintenance, will depend on how much work is involved.  However, once a day to once per week for just a few minutes is all it will take to keep your pool healthy year round.


If you water is still warm enough for algae to form, the pump should still be ran daily to maintain  clear water in your swimming pool.

Just like the chlorine, this can be reduced and quite significantly depending on how far you are into the off season.

I typically run my pool pump half of what I normally run it during the normal swimming season.  I run my pool pump 5 hours in the morning and 5 hours in the evening during the summer.  This is part due to higher electricity rates during the peak afternoon hours, so I have a timer to shut it off during that time.

After and before swimming season, but when the cover is not on the pool, I set my timer to just about 2.5 hours in the morning and the same for the evening hours.  I would recommend that you at least get 1 water turnover during the day.  Once your water has approached near 65 degrees, you can even drop these times in half again if you like, just before it is time to close your pool properly for the winter.


This is the most important part of knowing when you can officially close or open your swimming pool.  Remember opening does not mean time to swim, and closing does not mean the water is too cold.

When determining the average temperature if you check your water in the middle of the day when the temperature is warm, the water is going to read much higher than if you had tested it at night time.

This only makes sense as the water will rise and lower with the outside air temperature.

The best way to get a fairly accurate reading is to check your water temperature early in the morning at a time you choose and check it again about 10 to 12 hours later in the evening.  Add those two temperatures together and divide by 2 to get your average temperature.

Average water temperature = Morning reading + evening reading / 2

Close your pool once the average reading has fell to 65 or below and open it once the reading has exceeded 65 degrees.  In doing this, you will prevent algae and bacteria from growing while covered during the cool time of year.

You and your family will think each other when the next season arrives.  By following these simple guidelines you will find your water is as clear as the day your covered it when you finally get a chance to remove it and prepare for the summer. 

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