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As much as you enjoy the swimming season, at some point even this seemingly endless summer comes to an end.

When the temperatures drop and the outfit of the walkers goes back towards Eskimo, these are good indications that summer is coming to an end.

By this time, you’re probably already thinking about how to winterize your pool.

Sure, we also think it’s a shame that summer is slowly coming to an end. And, of course, no one wants additional work. However, there is no need to worry.

With our instructions on how to winterize your pool, the necessary work can be done in a matter of hours, and then it’s just a matter of waiting until the next swimming season.

Maybe you are a fresh pool owner or yet an old hand who just wants to make sure one more time, our guide is aimed at all groups and takes you step by step in winterizing the pool.

Why do you need to winterize a pool?

We are not spared from winters, so you can not avoid thorough preparations for winterizing it pool. The steps are important to avoid damage to the pool.

During the swimming season the pool is open. During this time, problems are usually limited to insects that want to make your pool your home, leaves that fall into the swimming pool, and other unwanted foreign objects. With a maintenance schedule that includes regular upkeep, none of this is a big deal.

In the winter, however, pool maintenance looks different. If the swimming pool remains unused in the winter, it is obviously not worthwhile to use a pool vacuum to suck impurities out of the pool in the sub-zero temperatures. However, without the necessary preparations, and especially in the case of an uncovered pool, you can expect a lot of work in the spring.

In addition to cleaning the water, you’ll need to rebalance the pool chemistry, and may even have to deal with frost damage. It can be dangerous for pool equipment if there is still water in hoses or the filtration system, which then freezes and spreads.

With proper preparation, pool winterizing is risk-free. Cold damage and pool water contamination are virtually eliminated with our tips. Just follow these instructions to save time, money and a lot of frustration. What more could you ask for?

When to winterize a pool

From when to when the pool season goes depends a bit on where you live. As a rule, not many people are willing to go swimming outside once the outdoor temperatures drop below 15°C. So depending on the weather, the swimming season can be sometimes longer and sometimes shorter.

One important reason why you should wait until temperatures drop is that higher temperatures encourage algae growth. The last thing you want is algae that can proliferate in the pool water over the long winter.

With the low temperature, algae growth is significantly inhibited, giving you plenty of time to thoroughly chemically clean the pool and ensure pool chemistry is balanced.

When the weather goes completely crazy and temperatures sometimes rise above 15 to 18°C during the winter months, you should take advantage of the time (and the good weather) to check the pool chemistry and balance it if necessary. In this way, you will ensure that no unpleasant surprises await you when you put the swimming pool back into operation.

Winterizing a pool step by step

A freezing winter can be dangerous for all types of pools. With the right preparation and equipment, you can avoid potential damage and ensure that you will have many more years of fun with your pool.

You usually always winterize an outdoor pool with water to protect the pool’s lining from the elements. The only exception to this are pools that can be set up and taken down quickly.

Step 1: Get the necessary material

Before you start winterizing your pool, gather the necessary materials and chemicals:

  • Pool shock
  • Algaecide
  • Alkalinity enhancer
  • Calcium hardness enhancer
  • Winterizing concentrate

We were particularly impressed by the following winterizing concentrate:

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In The Swim Pool Winterizing and
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  • Antifreeze
  • Test strip
  • Plug
  • Pool cover
  • Pool cover clips
  • Pool air cushions

Step 2: One last cleaning

Just as you wouldn’t put dirty laundry in the closet or put the dirty coffee cup on the kitchen shelf, you don’t winterize a pool completely without treatment.

You can start the next pool season without any nasty surprises if you clean your pool thoroughly at the end of the swimming season. To do this, vacuum the entire pool, remove foreign objects and brush the walls.

Cleaning the pool water makes the following steps much easier because, for example, the disinfectant will not be consumed by algae and other foreign organisms.

For inflatable swimming pools, this pool brush with soft nylon bristles is best:

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POOLAZA Pool Brush, 17.5" Pool
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Before the winter break, you can also send your pool robot on its last tour for this year.

Step 3: Test the pool water

An important step in pool winterizing is balancing pool chemistry. Take the five minutes to check your pool’s chemistry.

Test the water with test strips or a test kit. If you want to be really precise, you can also take a water sample and have it tested by an expert.

We were especially convinced by these test strips:

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Pool and Spa Test Strips - Quick
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The optimal values for the further steps and the winterization of the pool are:

  • pH: 7.4 to 7.6
  • Alkalinity: 100 to 150 ppm

Both values naturally decrease over time. Therefore, the high ends of the ranges are better because over the winter months the concentrations will drop again anyway.

Step 4: Correct the pool chemistry

Balanced pool water keeps out foreign organisms and prevents damage to the pool liner. So at the end of the season, apply the necessary chemicals to bring the water into balance.

Get the pH in the perfect range

Pool pH is one of the most important values in pool maintenance. This number ranges from 0 to 14 and indicates how acidic or alkaline the water is. The lower the value, the more acidic the water. Higher values represent a higher base content.

Even, those who are not chemistry teachers can measure the pool pH and correct accordingly:

If the water is too acidic (the pH is too low), you need to add a base. On the other hand, if the water is too basic (the pH is too high), you need to add acid.

We remember that the ideal pH for wintering is 7.4 to 7.6. Over winter, the pH will naturally drop. Therefore, when winterizing the pool, aim for a pH of 7.6.

To control pH, there are two chemicals, pH-Minus and pH-Plus:

  • pH-Minus is acidic and lowers the pool pH.
  • pH-Plus is alkaline and increases the pH value.

Chances are you will need pH-Plus because the optimal pH for winterizing the pool is higher than during the pool season.

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Pool Mate 1-2210B Swimming Pool pH
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Check the alkalinity

Alkalinity is a measure of the concentration of carbonates, bicarbonates, hydroxides and of other alkaline substances in the water. You should control alkalinity in the same way you did pH.

Due to natural circumstances, alkalinity decreases all by itself over time. The ideal range for alkalinity is between 100 and 150 ppm. You can increase the alkalinity with a proper booster. Just as with pH, it’s best to aim for the higher end of the range (i.e. 150 ppm) since you won’t be maintaining the pool for several months.

The right water hardness

You’ve probably heard of soft and hard water. And no, hard water does not mean ice.

The problem is rather the calcium hardness. Hard water with a high calcium content deposits calcium in the filter system and can therefore make for an unsightly, chalky layer.

On the other hand, water that is too soft is equally undesirable, because in this case the water will draw calcium from the pool. As a result, it can cause damage to tiled pools or to metal parts such as the ladder.

Therefore, by using chemicals, you need to control the calcium hardness to avoid damage such as to the plaster in soft water.

Vinyl pools are at least spared this problem, but even here damage to the metal can occur.

For increasing the calcium hardness as well as for decreasing it, there are appropriate agents that you can add to the pool. If the calcium hardness is too high, you can also simply add new filling water to dilute it and thus lower the calcium content. Just make sure that the fill water contains less calcium.

Aim for the 150 to 400 ppm range for calcium content. The ideal value is right in the middle at about 275 ppm.

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Step 5: Use winterizing agent

For anyone who doesn’t feel like getting out the white lab coat right now and isn’t a fan of scrubbing down the pool, winterizing agents are a great option.

These winter care products are a mixture of algaecide, which at the same time prevents the crystallization of mineral salts (i.e. the formation of lime scale) and dirt deposits. You will benefit from this during spring cleaning at the latest.

Simply follow the manufacturer’s instructions for dosing the chemical and you will save yourself some work when starting up the pool.

Note: If you want to lower the water level over the winter, do so before adding as winterizing agent to the pool so as not to use chemicals unnecessarily.

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In The Swim Pool Winterizing and
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Step 6: Perform shock chlorination

Perform a shock chlorination to ensure that the swimming pool is completely clean and that there is no algae left living in the pool.

Dosages vary from product to product, so simply follow the manufacturer’s instructions on the pool shocker packaging or brand manufacturer.

Shock chlorination of the pool is only ever done overnight because the main ingredient in the pool shocker – unstabilized chlorine – is broken down by solar radiation. Typically, chlorination with the normal calcium hypochlorite shock takes 8 hours.

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Note: Use a proper pool shocker, so the chlorine works quickly and then is quickly broken down by the sun. Normal chlorine granules would provide long-lasting chlorine levels that would be slow to decompose in cold water. The consequences would be fading, wrinkles and damage to the pool liner.

Step 7: Clean and seal the pipes

The pool filtration system is no different in any way from the plumbing that is installed in a house, for example.

Freezing of stagnant water in the pipes can cause serious damage as the ice spreads, which can be very costly, especially if the pipes are buried.

Flush the water out of the piping system and add antifreeze according to the manufacturer’s instructions.

Important: Use only antifreeze made for use with pools. For example, the antifreeze for the car is completely unsuitable and can cause damage to the piping system.

Next, seal the lines with rubber plugs. Don’t forget the waste water lines when doing this.

Step 8: Winterize the skimmer

Winterize the skimmer by first removing the skimmer basket. Store this in a dry place over the winter months.

Now either cover the skimmer with a skimmer cover or lower the water level below the opening of the skimmer so that no water can flow into it.

However, if there is precipitation (as rain or snow), you must make sure that the water can drain away.

Important: Never completely drain the pool over the winter. Because this will dry out the vinyl walls, which will significantly shorten its life.

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Note: Water that accumulates in the skimmer can freeze when temperatures drop. The expanding ice can then cause damage. We recommend covering the skimmer whenever you have a lot of precipitation in the winter.

Step 9: Winterize the pump

Turn on the drain plugs so that the water can drain out. Now remove the pool pump, all hoses, and anything else attached to the pump (chlorinator, for example).

Store all parts indoors to avoid unnecessary wear and tear.

Step 10: Winterize the pool filter

The correct procedure here depends on the type of filter:

Sand filter system

First, perform a backwash of the sand filter and then set the valve to “Winterize”. Then unscrew the drain plug. If your system also has a vent valve, you should unscrew it as well. It is best to store all the individual parts in the pump basket so that you can quickly find them again the next season.

At best, you can overwinter the sand filter system indoors. If the sand makes it too difficult to transport or if there is no parking space in the house, you can also leave the system outside. Just make sure that all drains are open so that no water can collect in the filter tank, which could then freeze.

Cartridge filter

Simply empty the filter cartridge and rinse it with a hose. Open the valves and store the cartridge indoors over the winter period.

Note: We always recommend storing indoors. This will increase the life of your pool equipment and protect it from damage due to the cold and weather.

For pool solar heaters, you will need to follow a similar procedure. To winterize, first drain the solar system completely. To do this, simply open the drain cock. If the system is operated with its own pump, you need to open the corresponding drain plug.

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Step 11: Clean and store the pool accessories

The pool accessories are also not designed to survive the cold season outside. It’s best to store the ladder, pool slide, swim toys, air mattresses and other accessories indoors. Otherwise, the accessories or, even worse, the pool may be damaged.

Corrosion of metal can also occur, which can then additionally lead to contamination of the pool water.

So collect all pool accessories. Everything that is not nailed down is first washed thoroughly with detergent and then stored in a dry place.

Step 12: Insert pool cushion

In regions where snow and ice are expected, these pool air pillows are a must for winterizing. The cushions are filled with air and then spread on the surface of the pool water. In this way, the overlying pool cover does not put so much stress on the walls of the pool.

The most important trick regarding the pool cushions is not to inflate them completely. Fill the cushions approximately 50 to 60% percent with air. This way, the air pillows can withstand some weight without bursting at the first pressure.

You can use a thin rope to keep cushions centered on the pool. To do this, you just need to pass the rope through an eyelet (pierced specially, if in doubt) and fix it on both sides of the pool.

Note: Centering the pool cushions is in fact not absolutely necessary. It is more of a precautionary measure. Especially if you have a higher number of cushions or a smaller pool, you don’t have to go through the hassle of using the cords.

Tip: Pool cushions have the problem of a notoriously short duration. However, you can extend this with some tape. To do this, simply tape all the seams of the cushions with a waterproof tape.

Step 13: Apply ice pressure pads.

As water freezes, it expands. The ice then presses against the walls of the pool, and this can cause expensive damage. The solution to this problem is simple (but also ingenious). When you float the so-called ice pressure pads in the water, the pressure of the expanding ice is transferred to the pads instead of the walls.

For optimal protection, the ice pressure pads are not randomly distributed in the water, but are attached as a chain along one long side and one short side of the pool. You can easily determine the number of ice pressure pads required. Measure the pool circumference and divide the value by two.

The ice pressure pads are sold exclusively as sets, so you can get a good quantity discount.

Step 14: Pull the pool cover over the pool

We’re almost done! The last step is to simply cover the pool with the pool cover. The pool cover should measure about 0.8 to 1 meter more than the inside dimension of the pool.

Then fix the tarp with cables, cable ties or clips. The icy winds in winter have a lot of power. For this reason, secure the pool tarp well so that it is really tight.

We are also big fans of DIY, but there is no room for improvisation here. At this point, please don’t use rocks, flower pots, or anything else that can damage the pool’s cover if it falls into the pool.

It is imperative that the pool cover you use is opaque to prevent the formation of algae.

During the winter, you should keep an eye on the pool cover from time to time and make sure that there is not too much water and snow accumulating on the pool cover. You may also need to lower the water level further if necessary.

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A final word

Let’s summarize everything once again. The pool water is clean and free of debris. The pool chemistry is balanced, and all pool accessories have been winterized or are safe and secure in the dry. The pool cover has been pulled onto the pool and is supported by several pool cushions.

Once you have mentally checked off all these points, there is nothing more to do. Now it’s time to put your feet up, snuggle up even more in the blanket and wait for the next pool season to start.

Got a saltwater pool? Check out our guide on how to winterize a saltwater pool.

Larry has been a true water rat since childhood. Pure pleasure turned into a passion. That's why he is the first point of contact for friends and acquaintances when it comes to pool-related problems. He is an integral part of the PoolHandbook editorial team.