How to

24 November 2016

Preparing Your Swimming Pool for Winter

Img source: istra1977, via Wikimedia Commons

Properly ensuring that your swimming pool is ready for winter can save you lots of money and trouble. By closing it up a few weeks before the weather turns ice cold, you can protect its internal workings from freeze damage, a serious hazard for pool machinery. However, you don’t want to do it too early, as temperatures above around 15°C can allow algae growth. Once the temperature drops significantly below that, algae growth will be slowed or even stopped. One quick way to decide exactly when is to ask any neighbours with similar pools when they usually do theirs. In this, article, we’ll give you a step-by-step guide on how to carry out the “winterization” of your pool once you’ve decided when to begin.

Safety Steps

Wear a Mask


Putting on a ventilator or dust mask keeps harmful chemicals out of your lungs. There are plenty of chemicals involved in pool maintenance, and fumes, mists, or granules of them can be nasty if you inhale them.

Wear Goggles and Rubber Gloves


With all the potentially harmful chemicals about, it’s not just your lungs that need protection. Wearing gloves keeps your hands safe when handling them, and goggles keep them out of your eyes. Also wearing old clothes is advised, as chemicals can mess up your nice ones if you’re not careful.

Don’t Add Water to the Chemicals


When mixing any chemicals with water, never add water straight into the chemical bucket, as this can cause them to fire out or mix improperly. Instead, add the chemicals to already filled up water containers.

Follow Chemical Label Instructions


This may sound obvious, but label instructions are there for a reason. Follow them!


Balancing the Pool’s Chemistry


Adjust pH, Alkalinity, and Calcium Levels


By ensuring that all of these are at the correct level, you can prevent any potential corrosion or scale buildup from occurring over the winter. You should perform the balancing about 5 days before you close the pool. Levels should be as follows:
  • pH: 7.2 - 7.6
  • Alkalinity: 80 - 120 ppm
  • Calcium: 180-220 ppm (depending on product instructions).

Shock the Water


Shocking” the water refers to using an extra-strong chlorine or chlorine substitute to kill most of the bacteria, fungi, and algae that live in the pool. Buy a strong shocking product, with at least 65% sodium hypochlorite. Fill a large bucket with pool water, add the product to the recommended concentration, then pour it into the pool whilst the filtration system is running. As you’re using such a strong shock product, you should stay out of the pool at this time.

Add Winterizing Algaecide


Algaecide kills any algae already present that the chlorine didn’t get, and prevents further blooming. Algae can discolour the pool, make it smell, and block the filter, so you definitely want to get rid of it. Wait until the pool has normalised from the shock treatment before you add the algaecide.

Clean the Pool

All of this cleaning should be done the day you close the pool, to make sure no dirt or contaminants get back in.

Remove all Pool Equipment

This means anything that’s not water, basically, including filters and pumps. Rinse it all out then lay it out to dry, before storing it in a safe, dry place.

Skim the Pool

Use a skimming net on a pole to remove all debris from the pool. Empty the skimmer traps and the pump leaf catcher.

Vacuum and Brush the Pool

Use a pool vacuum to clean out any remaining debris, then use a pool brush to scrub the sides and bottom of the pool.

Lower the Water and Drain Equipment

Use a Pump to Lower the Water

Sometimes this can be done with the pool’s main drain pump. Other times, you may have to use a vacuum pump to suck water out of the pool.

The pool should be lowered to the following levels:
  • Mesh cover: 12 to 18 inches.
  • Solid floating cover: 3 to 6 inches.

Drain Equipment

Drain all pumps, filters, heaters, and chlorinators fully. If any water freezes inside of them during winter the expanding ice could ruin them. Most pool equipment has built in drains for you to do this.

Clean the Filter

Drain and open the filter case, then clean it extremely well. Regardless of filter type, it must be extremely clean to ensure effective performance after winter’s over.

Winterize Plumbing

The pipes that bring water to and from your pool also need to be dried out to avoid frozen cracking. You can do this with a vacuum on the blow setting.

Alternatively, you can add special swimming pool antifreeze to the pipes to prevent damage.

Finish Closing the Pool

Cover the Pool

Floating covers are not enough to seal the pool on their own. You should add a full pool cover on top to keep out all dirt and debris. Anchored safety covers are perhaps the best, given that they are sealed, and prevent children or pets from wandering in. Alternatively, you can use lowered covers that sit on the water and go up the walls.

Make sure to fold away any excess cover, and weigh it down with water bags if it’s not an anchored one.



And that’s that, your pool is all cleaned and safely tucked away, ready to be all fresh when you open it up in spring. If you’ve got some extra spare time, why not prepare the exterior of your home for the onrushing winter months?



Sam Franklin

With a master’s in Literature, Sam inhales books and anything readable, spending his working hours reformulating the info he gathers into digestible articles. When not reading or writing, he likes to put his camera to work around the world, snapping street photography from Stockholm to Tokyo. Too much of this time spent in Japan teaching English has nurtured a weakness for sashimi, Japanese whisky, and robot caf├ęs.