JavaScript seems to be disabled in your browser. For the best experience on our site, be sure to turn on Javascript in your browser.
Customer Service: [email protected]
What Chemicals Should I Put in My Pool When Closing?
As those warmer summer temperatures start to fade away, it’s time to think about closing your pool for the off-season. If the winterising process is on your mind and at the top of your do-to list, one of your main priorities is likely what swimming pool chemicals you need to close your pool for the winter. Here’s a guide to the essential things you should do to closing your pool:
Aside from adding the right chemicals to the water, there are a couple of other key maintenance tasks you’ll need to perform when closing. Following a thorough winterising checklist will help ensure your kit is in good condition when you open back up in spring.
For guidance on the other essential winterising tasks, please see our full guide to closing your pool for winter.
As always, you’ll need to start by assessing the quality and current chemical levels of your water to see exactly what/how much needs to be added. You can use water test strips to quickly and accurately check your chlorine, pH, total alkalinity and calcium hardness levels.
Remember, the wrong chemical levels can cause severe damage to your pool and equipment, which may void product warranties on items like pumps and filters. Regular testing is key to maintaining a healthy and safe swimming environment.
AquaChek Yellow -
Chlorine Chemical Test Strips
Safe Swim Photometer -
Chemical Digital Meter
Lovibond Chlorine/pH -
Chemical Pooltester Kit
If you’ve kept on top of your regular chemical maintenance, there shouldn’t be too much to do when closing, and you’ll be familiar with the what and the why. The key winter pool chemicals you’ll require include:
One of the main things you’ll do to prepare for winter closure is shocking your pool. A strong dose of chlorine or a non-chlorine oxidiser will kill lingering contaminants, bacteria and algae, so you don’t get anything nasty growing underneath your pool cover only to be revealed when spring rolls around again.
Removing existing algae and organic pollution gives your algaecide the best chance of success, essentially providing a blank slate for it to keep clean. Aim to do this five or so days before fully closing your pool and securing your winter cover. This is because the shock will need time to circulate, and you’ll need to wait until the chlorine levels have dropped to the recommended level before adding any other chemicals
Once your water has been treated with a shock (and left for the requisite time), you can add a dose of long-life algaecide. Long-life algaecide products are designed to stay working in your water for up to three months per application. During this time, the algaecide will inhibit the growth of new algae, keeping your water clear and clean.
You’ll usually come across two kinds of algaecide: copper-based and copper-free. Copper sulphate is very effective at stopping algae from growing in your pool, which is why it’s used. However, adding more copper to pools that already have high metal levels can lead to scaling and staining. If this is a problem for your pool, it’s best to opt for copper-free algaecides! If you’re using algaecide for winter closure, ensure you make the distinction between long-life algaecide and algae controllers. One dose of long-life algaecide should take you through a good portion of the off-season, but other algaecides may be intended for more frequent application. You might come back to some nasty surprises if you do not reapply them.
Winter closing kits can be useful because they provide everything you need for the job, but some kits quickly become unnecessarily complicated, including specialist chemicals you might find you don’t actually need.
This is why our winter pool closing kit keeps it simple with quality chlorine shock and long-life algaecide, ensuring you’re equipped with the absolute essentials. When you buy this as a kit, the price is less than if you were to buy the chemicals separately. So, if you need to stock up on both for the off-season, we’d recommend getting the two chemicals in the kit!
Pool Opening and Closing
Chemical Kit
Long Life Copper Free
Algaecide
Sodium Hypochlorite /
Liquid Shock
As with your other regular pool maintenance chemicals, carefully read the dosage and safety instructions. Pay attention to the manufacturer's guidance for specific chemicals, as the doses or handling instructions may differ slightly between brands.
Once you’ve added your winterising shock and algaecide, you can cover your pool with a sturdy winter cover to keep debris and sneaky contaminants out. However, even though it’s covered, it’s a good idea to monitor the water’s chemical levels and test them every now and again to check whether anything needs to be adjusted.
For a bit of advice on post-winterising tasks like this, check out our top tips for swimming pool maintenance in winter.
Ultimately, with the right chemicals and care, you should have no trouble closing your pool this season. For more guidance on winter closure or any other common pool queries, browse our blog.
At 1st Direct Pools, we stock all the essential chemicals you need to close your pool with confidence. From chlorine shock and algaecides to pH balancers , we have everything required to protect your pool throughout the winter months.
Pool Shock Dosage Advice: How Much Chlorine Shock Should You Add?
What Size Swimming Pool Heat Pump Do I Need?
How to Prevent and Remove White Water Mould
Pool Chlorine Tablets Vs Granules: Which are Better?
How Often Should You Replace Your Swimming Pool Filter?
To close your pool for the season effectively, you'll need to add pool shock, algaecide, and a pH balancer to ensure your water stays clean and balanced throughout the winter months. Our complete pool opening and closing chemical kit includes both shock and algaecide and is available in two sizes to suit your pool's water volume. Adding shock will help eliminate lingering contaminants and stabilise chlorine levels, ensuring your pool is free of bacteria while it’s closed. Follow this with a powerful algaecide to prevent algae growth—saving you the hassle of dealing with a slimy, green pool when reopening in the spring. For best results, use these chemicals as directed and conduct occasional winter checks to ensure your pool is secure and the chemicals remain effective.
Yes, shocking the pool helps eliminate contaminants, ensuring clean water when you reopen the pool in spring.
Yes, chlorine tablets can be used to maintain low chlorine levels and prevent algae growth during the winter months.
No, pool shock contains higher concentrations of chlorine or other oxidizers to quickly raise chlorine levels and kill bacteria or algae.
Yes, natural alternatives include saltwater systems, ozone generators, and mineral purifiers, which reduce the need for traditional chlorine use. However, it’s important to note that natural methods like saltwater systems still produce chlorine, just at lower levels.
While natural alternatives are available, chlorine remains the best choice for pools due to its affordability and compatibility with most equipment. If you have sensitive skin, bromine is another option, but it’s best suited for indoor pools as sunlight causes it to degrade more quickly. Do keep in mind that bromine is a much pricier alternative to chlorine.
