Winterizing Your Pool without Chemicals

Having your own pool in the garden is a joy, but it also comes with a lot of responsibilities. Besides regular cleaning, it's necessary to winterize it as the low temperatures arrive – otherwise, the frost can irreparably damage the pool. How should you proceed?



When to Winterize the Pool and How to Begin?

Winterizing comes into play when the water temperature consistently drops below 15°C (59°F). If you winterize the pool at higher temperatures, you increase the risk of algae and other harmful microorganisms multiplying, which will make reopening the pool more challenging.

For modern vinyl and plastic pools, you don't completely drain the water. Its pressure actually secures the vinyl to the walls and floor and creates a counter-pressure on the ground beneath the pool. This approach also saves the environment and your wallet; with proper treatment, you can reuse the water in the next year.

In the first step, dismantle all removable accessories – steps, lights, or skimmer baskets. Use a net to collect fallen leaves, bits of branches, and other debris from the surface. Thoroughly brush the pool walls and use a pool vacuum to clean the bottom.

Preparing Pool Water before Winterizing

Take care of the pool water until winterization in the same way as during the summer. It should not contain potentially harmful microorganisms or substances that irritate the skin or mucous membranes (as is the case with chlorine disinfection, see below).

Shortly before winterizing, measure the pH of the water using test tablets, a tester, or electronic equipment. If the result falls outside the ideal range of 7.2 to 7.6, adjust the pH with suitable preparations, wait for a while, and recheck the water's acidity/alkalinity.

A crucial step (not only before winter) is water disinfection. Chlorine-based disinfectants, which were previously commonly used, are slowly being phased out – partly because chlorine, when reacting with organic impurities and pathogens, produces harmful trichloramines. These give pools their typical "chlorine" smell and lead to various health problems, such as:

  • mucous membrane irritation,
  • breathing problems and asthma development,
  • conjunctival irritation and watery eyes,
  • allergic reactions.

Article Tip: How to Clean a Pool Without Chemicals

Photocatalytic Coating – the Path to Long-Term Disinfection

An alternative to chemical disinfection is low-pressure UV systems, which eliminate harmful substances and microorganisms based on physical principles. The eco-friendly pool cleaner FN NANO® AQUA functions similarly. It surrounds microorganisms and organic impurities with titanium dioxide nanoparticles and eliminates these unwanted elements in the pool through oxidation.

FN NANO® AQUA activates UV light, which is part of sunlight. For indoor pools, you need to activate the product with special UV lamps. Nanoparticles also adhere to the pool's floor and walls. 


With long-term use, FN NANO® AQUA forms a functional coating with disinfectant properties. It effectively eliminates any microscopic impurities that may enter the pool during winter. The product's major advantage is its health safety. When applying the suspension, you can stand directly in the pool and evenly distribute the product into the water.


Draining Technical Elements and Lowering the Water Level

Utilize the treated pool water for backwashing the sand filter. Then remove trapped impurities and drain the water using a backwash valve. Follow the manufacturer's recommended procedure, but in general:

  • For a 4-way valve, set it to "winter" mode,
  • For a 6-way valve, turn it to any intermediate position (leave it in this position until spring).

Lower the water level by 25 cm (about 10 inches) below the lowest functional/technological element of the pool (this could be a skimmer, jets, or a counterflow system).

For pipes that carry water between the filtration system and the pool, a little below the ground, there is a risk of freezing, so use drainage screws. The specific process depends on the slope of the pipe distribution (water will either flow into the pool or the basement). If there is no slope, suction the water out.

Drain the pump as well, and store it, along with the filtration system, in a place where the temperature doesn't drop below 5°C (41°F).

Protect the inside of the skimmer from freezing by inserting a plastic expansion plug, while rubber plugs will achieve the same effect for the jets. Finally, cover the pool with a winter cover.

Key Takeaways from the Article

  • Winterize the pool when the water temperature falls below 15°C (59°F) due to weather conditions. Continue filtering and treating the water, even if you won't be swimming in it. With proper treatment, you can reuse it in the next season.
  • Shortly before winterization, adjust the water's pH to a value between 7.2 and 7.6 and apply a disinfectant.
  • An alternative to irritating chlorine-based disinfection is the health-safe product FN NANO AQUA. It eliminates harmful pathogens and organic residues in the water using titanium dioxide nanoparticle technology and forms a photocatalytic, disinfectant coating on the pool walls and floor with long-term use.
  • During winterization, backwash the sand filter and lower the pool's water level by about 25 cm (10 inches) below the lowest technical element.
  • Drain all pipes and equipment, and cover the pool with a winter cover or pool pillow.


Exposure to trichloramine and respiratory symptoms in indoor swimming pool workers
Photolysis of inorganic chloramines and efficiency of trichloramine abatement by UV treatment of swimming pool water

Lukáš Konečný, Strategy and business development, nanoSPACE
Lukáš Konečný has been active in the nano field since 2015. He graduated from the University of Economics and Business and has long been involved in digital marketing, digitisation and automation of advertising for technology companies and online projects. At nanoSPACE, Lukáš has been in charge of strategy and business development since May 2020.