Best Pool Winterizing Chemicals of 2025

Toby Butcher Avatar
Toby Butcher
Last Updated: 2 Feb 2025

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As the colder months approach, it's important to properly winterize your pool to protect it from damage. One key aspect of this process is using pool winterizing chemicals. These products are specifically designed to help maintain water quality and prevent algae growth during the winter months when the pool is not in use. They can also help to stabilise the pool's pH levels and protect against corrosion. While there are many different types of pool winterizing chemicals available, it's important to choose the right ones for your specific pool and to follow the manufacturer's instructions carefully.

At a Glance: Our Top Picks

Cleenly Pool Winteriser for Winter Protection Cover #TOP 1
Cleenly Pool Winteriser for Winter Protection
ftb score rating icon 9.9
Cleenly Pool Winteriser for Winter Protection Cover #TOP 2
Cleenly Pool Winteriser for Winter Protection
ftb score rating icon 9.8
LO CHLOR Pool Winterising Algaecide Kit Cover #TOP 3
LO CHLOR Pool Winterising Algaecide Kit
ftb score rating icon 9.6

Top 10 Pool Winterizing Chemicals

#TOP 1

Cleenly Pool Winteriser for Winter Protection

Cleenly Pool Winteriser for Winter Protection Cover
Cleenly Pool Winteriser - Protects Your Pool, Hot Tub or Spa Throughout Winter - Prevents Limescale, Algae & Mineral Staining (5 Litres)

The Cleenly Pool Winteriser is designed to protect your pool, hot tub, or spa throughout the winter months. This product helps prevent limescale, algae, and mineral staining, ensuring your pool remains clean and ready for use when winter ends. It is easy to use, as the formula can be added directly into your hot tub water, saving you the hassle of emptying it out. Furthermore, it has been tested for safety with all types of hot tubs, spas, and pools, giving you peace of mind during the colder season.

What We Like
Easy to use formula
Prevents limescale and algae
Safe for all pools and spas
Winter protection for your pool
Ready for use after winter
#TOP 2

Cleenly Pool Winteriser for Winter Protection

Cleenly Pool Winteriser for Winter Protection Cover
Cleenly Pool Winteriser - Protects Your Pool, Hot Tub or Spa Throughout Winter - Prevents Limescale, Algae & Mineral Staining (10 Litres)

The Cleenly Pool Winteriser offers excellent protection for your pool, hot tub, or spa throughout the winter months. It effectively helps prevent limescale, algae, and mineral staining, ensuring your water remains clean and ready for use when spring arrives. You will appreciate the convenience of adding the formula directly into your hot tub water, eliminating the hassle of emptying it. This product is safe for all pools and spas, making it a reliable choice for winter maintenance.

What We Like
Prevents limescale and algae
Easy to use formula
No need to empty water
Safe for all pools and spas
#TOP 3

LO CHLOR Pool Winterising Algaecide Kit

LO CHLOR & BLUE HORIZONS
LO CHLOR Pool Winterising Algaecide Kit Cover
LO CHLOR & BLUE HORIZONS ABOVE GROUND POOL & SMALL POOL LONG LIFE ALGAECIDE WINTERISING KIT

The LO CHLOR Winterising Kit is an essential solution for maintaining your pool during the colder months. It includes a 720g multifunctional chlorine tablet dispenser, ensuring your pool remains sanitised effortlessly. The 175g Pool Fusion shock treatment is perfect for clearing up any winter-related issues, treating pools of up to 5,000 gallons with ease. Additionally, the kit features a 500ml super strength long-life algaecide, effective for pools up to 13,000 gallons, providing protection from algae throughout winter and into summer. A free winterisation guide is also included to help you through the process.

What We Like
Comprehensive winter pool care
Effective against algae growth
Easy-to-use shock treatment
Includes helpful winterisation guide
#TOP 4

SeaKlear AquaPill AP71 WinterPill for Pools

AP71
1 count (Pack of 1)
SeaKlear AquaPill AP71 WinterPill for Pools Cover
SeaKlear AquaPill AP71 WinterPill Swimming Pool Winterizer Pill, Translucent Light Yellow, Pack of 1

The SeaKlear WinterPill is designed to float under your winter cover throughout the season, ensuring continued protection for your pool. It works effectively with mesh safety covers, providing peace of mind during the colder months. With its patented 6-month delivery system, you can rely on consistent performance without frequent reapplication. Additionally, this product is safe for all surfaces and filters, making it a versatile choice for pool owners who want an all-in-one solution for winterising their pools.

What We Like
Easy to use all season
Compatible with mesh covers
Long-lasting performance
Safe for all pool surfaces
#TOP 5

Sikasil Pool High Chlorine Resistant Sealant

Sika
150295
300 ml
Sikasil Pool High Chlorine Resistant Sealant Cover
Sikasil Pool with High Chlorine Reristance Silicone Sealent for Swimming Pools and Wet Areas - White - 300 ml

The Sikasil Pool Sealant is specially designed for swimming pools and wet areas, ensuring high chlorine resistance essential for maintaining hygiene. Its exceptional resistance to fungal attacks is crucial for keeping your pool clean and safe. Additionally, this sealant offers excellent UV and weathering resistance, meaning it will withstand the elements and maintain its integrity over time. You will appreciate its high tear resistance, which adds to the longevity and durability of your pool maintenance efforts.

What We Like
High chlorine resistance
Fungal attack resistant
Excellent UV resistance
Durable and flexible
#TOP 6

Relax Cleaner Winter Algicide Treatment 1 Litre

Relax
Relax Cleaner Winter Algicide Treatment 1 Litre Cover
Relax Cleaner Winter Concentrate 1 litre - Non-Copper Longlife Algicide

The Relax Winter Algicide is an effective winter swimming pool treatment designed to keep your pool clean during the colder months. One litre of this concentrated formula treats up to 10,000 gallons or 45,000 litres of water, making it an economical choice for pool maintenance. By using this product, you ensure that your pool remains free from algae growth, allowing for a hassle-free opening come spring. Additionally, it is available for delivery across the UK mainland, providing convenience at your doorstep.

What We Like
Effective winter treatment
Treats large water volume
Prevents algae growth
Convenient UK delivery
#TOP 7

Tamar Winter Dispenser for Pools 2 kg

Tamar
Dosf
White
15x15x29 cm
Tamar Winter Dispenser for Pools 2 kg Cover
Tamar Winter – Dispenser AUTOMATICO 2 kg GENERICO

The Tamar Winter Dispenser is designed for convenient pool winterising. It comes in a 2 kg pack of tablets, allowing you to easily manage the dosage based on your pool size. This ensures that your pool receives the right amount of treatment for optimal protection. You will appreciate the floating packaging feature, which helps you track when the product is complete, making maintenance straightforward and hassle-free.

What We Like
Easy dosage adjustment
Clear tracking of usage
Convenient floating packaging
Suitable for various pool sizes
#TOP 8

Bayrol PURIPOOL Super 6L Winterising Product

EAN4008367431686
No Color
Bayrol PURIPOOL Super 6L Winterising Product Cover
Bayrol PURIPOOL SUPER 6L PRODUIT HIVERNAGE 2243168

Bayrol PURIPOOL Super is a highly effective winterising product designed for swimming pools. With a 2 KG quantity sufficient for 40 M², it offers excellent coverage for your pool area. The easy application ensures you can prepare your pool for the colder months without hassle. Its comprehensive formula caters to all types of pool cultures, making it a versatile choice for any pool owner. This product simplifies the winterising process, allowing you to protect your investment effortlessly.

What We Like
Easy application
Good coverage
Comprehensive formula
Suitable for all pools
#TOP 9

Natural Chemistry Phos Free Pool Cleaner 3L

Natural Chemistry Phos Free Pool Cleaner 3L Cover
Natural Chemistry 05121 Phos Free Pool Cleaner 3 Liter

The Natural Chemistry Pool Cleaner is designed to keep your swimming pool algae-free. This phosphate-limiting additive helps prevent the growth of unwanted algae, ensuring a cleaner pool environment. With its ability to soften water, it reduces the need for frequent filter changes and vacuuming, making maintenance easier for you. Additionally, this product enhances any existing sanitiser system while being completely safe for both your family and the environment. Enjoy a clearer pool without the worry of harmful chemicals.

What We Like
Prevents algae growth effectively
Reduces maintenance tasks
Safe for family and environment
Enhances sanitiser systems
#TOP 10

SeaKlear Winterpill Pool Closing Chemical 2-Pack

AP75-02
White
2-Pack
SeaKlear Winterpill Pool Closing Chemical 2-Pack Cover
SeaKlear AP75-02 15K Winterpill Pool Closing Chemical, 2-Pack, White

The SeaKlear Winterpill is a concentrated pool closing chemical designed to keep your pool in top condition throughout the winter. It effectively reduces scum lines, ensuring that your pool remains clean during the off-season. This product helps maintain clear water, making it easier for you when it's time to open your pool again. Additionally, with one WinterPill capable of treating up to 15,000 gallons, you benefit from a faster turnaround time, allowing you to enjoy your pool sooner.

What We Like
Highly concentrated formula
Reduces scum lines
Keeps water clear
Fast turnaround at opening
Treats up to 15,000 gallons
Buying Guide Image

Frequently Asked Questions (FAQs)

1. What chemicals do you put in pool for winter?

What chemicals do I need to close my pool?. Chlorine.Pool Shock.Soda Ash.Baking Soda.Muriatic Acid.Winter Algaecide.Pool Antifreeze.Stain and Scale Prevention.

2. Are pool winterizing chemicals necessary?

You really only need one chemical (algaecide) to properly winterize a swimming pool. You need some other stuff to protect your pool from harsh winter conditions, but only one chemical to add when closing.

3. What do you put in pool to close for winter?

After draining the water to winter levels, put antifreeze in the skimmer opening to prevent water from freezing in the pool's plumbing lines. Most pools require approximately 1 gallon of antifreeze to ensure the plumbing is protected.

4. What chemicals do I need to close my above ground pool for the winter?

Before you winterize your above ground pool, make sure you've got the necessary supplies: Winterizing chemical kit or pH increaser, Alkalinity increaser, Calcium hardness increaser, Pool shock, and Algaecide. Clarifying enzyme supplement (optional, but recommended)

Editor's Notes

During our pool winterizing chemical research, we found 13 pool winterizing chemical products and shortlisted 10 quality products. We collected and analyzed 71,635 customer reviews through our big data system to write the pool winterizing chemicals list. We found that most customers choose pool winterizing chemicals with an average price of £29.06.

The pool winterizing chemicals are available for purchase. We have researched hundreds of brands and picked the top brands of pool winterizing chemicals, including Cleenly, LO CHLOR & BLUE HORIZONS, SeaKlear, Sika, Relax. The seller of top 1 product has received honest feedback from 545 consumers with an average rating of 4.8.

Written by
Toby Butcher Avatar

Toby Butcher is a Horticulturist, and he earned his title as a Master Gardener in 2016. Toby has acquired a 25-year experience as a home gardener planting, designing, grooming vegetables and flowers. He is the leader of a plant group in Durham. Toby owns a blog where he publishes articles on growing and growing your flowers at home, in a vase, or in a garden.