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Sometimes the problem is too much sunshine
Most of the time, British pool owners worry about keeping their water warm. Then a proper heatwave arrives. The sun beats down for days, the nights stay muggy, and suddenly your lovely garden pool feels more like a bath than a refreshing dip.
It’s a nice problem to have, but it is still a problem. Water that gets too warm can feel flat and unrefreshing. It also puts extra pressure on your water care, because algae and bacteria enjoy the heat as much as we do.
That’s where cooling pool water comes in. In this guide we’ll explain why pools overheat, which simple habits help, and which pieces of equipment can make a real difference. We’ll keep it practical and plain.
Who this guide is for
It’s for anyone with an outdoor pool, swim spa or spa in the UK who has noticed the water creeping up during a hot spell. It’s also useful if you are planning a new pool and want to design with summer comfort in mind.
Why your pool water gets too warm
A pool is a big solar collector. Every hour of direct sunshine pours energy into the water, and the water holds on to it. Understanding where that heat comes from makes it much easier to manage.
Here are the main culprits:
- Direct sun. Long, cloudless days add warmth hour after hour, especially in a south facing garden.
- Warm nights. Normally a pool loses heat overnight. In a heatwave, the air stays warm and the water barely cools.
- Dark surfaces. Darker pool finishes and dark paving around the pool absorb more heat.
- A cover left on. A cover is brilliant for holding heat in. In a heatwave, it can hold in more than you want.
- Heating left running. It sounds obvious, but heating settings are easy to forget when the weather turns.
- Small volume. Smaller pools and spas warm up faster because there is less water to heat.
What counts as comfortable
There’s no single right answer. Many people find a pool refreshing when it’s a few degrees cooler than a typical indoor heated pool. Keen swimmers often prefer it cooler still, while young children and older relatives may like it a little warmer. The key is to decide what feels right for your family, then keep the water temperature steady around that point.
Simple habits for a cooling pool in a heatwave
Before you think about equipment, start with the easy wins. Small changes to how you run the pool can take the edge off quite quickly.
Turn off or lower the heating
Check your heater settings first. If your system has a thermostat, set it to a lower target or switch heating off completely during a hot spell. Many modern systems let you do this from your phone, which makes it easy to adjust as the weather changes.
Take the cover off at night
This is one of the simplest tricks. Leave the pool open overnight so heat can escape into the cooler night air. Then put the cover back on first thing in the morning, before the sun gets strong. A cover on a hot day helps block some of that direct sunshine.
Please remember that an open pool is a safety risk. If the cover comes off at night, make sure your garden is secure, gates are closed and children and pets cannot reach the water.
Run the pump at night
Moving the water helps it lose heat. Running your circulation overnight rather than during the hottest part of the day can help the surface give up warmth. Your filtration also has more work to do in a heatwave, so longer run times often make sense anyway.
Use water features
Waterfalls, deck jets and fountains all throw water into the air. As it falls back, a little evaporation happens, which carries heat away. It won’t transform your pool on its own, but it all helps. Our guide to pool water features explains the options.
Shade makes a real difference to your cooling pool
The most effective way to stop water overheating is to stop the sun reaching it in the first place. Shade does exactly that, and it makes the whole area more pleasant for people too.
Here are some ideas to consider:
- Sail shades. Tensioned fabric sails can cover part of the pool and surround. They look smart and can be taken down in winter.
- Pergolas. A pergola with slatted roof or climbing plants creates dappled shade over a seating area and part of the water.
- Large parasols. Cantilever parasols can be angled through the day to follow the sun.
- Trees and planting. Well placed trees give lovely natural shade, although falling leaves mean more cleaning.
- Enclosures. A pool enclosure with vents or opening sections can help control both heat and debris.
Think about the surroundings
Paving and decking around the pool can get very hot. Lighter coloured paving stays cooler underfoot and reflects heat rather than soaking it up. Planting and grass around the edges also help keep the whole space cooler. If you’re planning a new pool, it’s well worth thinking about this early. Our pool landscaping guide has plenty of ideas.
Equipment that can help
Sometimes habits and shade aren’t quite enough, especially with a smaller pool or a spa that sits in full sun. That’s when equipment comes into play.
Heat pumps with a cooling mode
Some pool heat pumps can run in reverse. Instead of taking heat from the air and putting it into the water, they take heat from the water. Not every model offers this, and how well it works depends on the unit, the size of the pool and the conditions. If a cooling pool feature matters to you, mention it early so it can be factored into your equipment choices. We can talk you through what’s realistic for your setup.
Covers and the right cover type
Covers come in different styles. Some are designed to capture heat, which is great for spring and autumn. Others are better at reflecting sunlight. An automatic cover makes it easy to open and close the pool at the right times of day. We look at the pros and cons in our guide to automatic pool covers.
Smart controls
Smart pool control systems can show you the water temperature at a glance and let you change heating and pump schedules from anywhere. That makes it much easier to respond when a heatwave is forecast.
Topping up with fresh water
Adding fresh water from the mains will cool the pool slightly, but only a little in most cases. It also dilutes your chemical balance, so test and adjust afterwards. Please don’t drain large amounts of water to cool the pool. That can upset the balance badly and, with some pool types, draining carries structural risks. Always ask a professional first.
Spas and swim spas need a slightly different approach
Spas and swim spas hold far less water than a garden pool, so they warm up quickly and hold that heat well. Their insulated cabinets and thick covers are designed to keep energy in, which is exactly what you want for most of the year. In a heatwave, the same design can work against you.
Here are a few things that usually help:
- Lower the set point. Most spa controls let you drop the target temperature, and some let you switch heating off entirely for a while.
- Open the cover in the evening. Fold it back for an hour or two once the sun has gone down, as long as the area is secure.
- Use economy or filter only modes. These reduce how often the heater kicks in while still keeping the water moving.
- Move shade, not the spa. A parasol or sail shade over the spa often does more than anything else.
Treat a spa as a small cooling pool project in its own right. The principles are the same, but the changes you make tend to show results faster because there is less water involved. If your spa seems to overheat even with the heater off, the pump may be adding warmth through long run times, so it’s worth asking us to take a look at the settings.
Warm water needs extra care
Hot weather changes your water chemistry. Warm water uses up chlorine faster, and algae can appear surprisingly quickly. The busier your pool is, the more work the sanitiser has to do.
Here’s how to stay on top of things during a hot spell:
- Test more often. Daily testing is sensible in a heatwave.
- Keep sanitiser levels steady. Top up as needed rather than waiting for problems.
- Watch the pH. Balanced pH helps your sanitiser work properly.
- Clean the filter. A busy filter clogs faster in summer.
- Brush and skim. Remove debris before it breaks down in the water.
When you handle any pool chemicals, always follow the label. Wear gloves and eye protection, never mix chemicals together, and always add chemical to water, never water to chemical. Keep swimmers out until the water is balanced again, and store everything safely away from children and pets.
If the water turns green or cloudy, don’t panic. Our guides to pool algae and cloudy water walk you through what to do, and we’re always happy to help if you’d rather leave it to us.
Designing a pool that stays comfortable all summer
If you’re still at the planning stage, you have a great opportunity to think about summer comfort from day one. A little forethought now saves a lot of fiddling later. Building a cooling pool into the plan from the start is far easier than fixing an overheating one afterwards.
Things worth discussing with your installer:
- Where the pool sits in relation to the sun through the day
- Whether shade structures could be part of the design
- The colour of the pool finish and surrounding paving
- Which heating system you choose and whether it can cool as well
- The right cover for your pool and lifestyle
- Smart controls so you can manage everything easily
A one-piece pool is quick to install and comes with a smooth, easy clean finish. Pair it with good shading and sensible controls and you’ll have a pool that feels inviting in every season. You can explore our full range of pools to see what might suit your garden.
Heatwave questions we get asked a lot
Can I cool my pool with ice?
In practice, no. You’d need an enormous amount of ice to make any noticeable difference in a garden pool. Shade, night circulation and leaving the cover off overnight are far more effective.
Should I leave the cover on in a heatwave?
It depends on the time of day. Many owners take it off at night to let heat escape, then put it back in the morning. Always keep the area secure when the pool is uncovered.
Does a heat pump always have a cooling function?
No. Some do and some don’t. If it’s important to you, ask about it before choosing equipment.
Is warm pool water unsafe?
Warm water isn’t dangerous in itself, but it can make water care harder. Test more often and keep sanitiser levels steady.
Will running the pump more help?
It can. Circulating water overnight helps it shed heat, and it keeps your filtration working well while the pool is busy.
Can you help if my pool keeps overheating?
Yes. We can look at your setup, your heating settings and your cover, and suggest practical changes.
Enjoy a cooling pool all summer long
A heatwave should be the best time to own a pool, not a frustrating one. With a few simple habits, some well placed shade and the right equipment, you can keep your water refreshing even on the hottest days. The aim is steady water temperature that feels just right for the people using it.
If you’d like help choosing equipment, adjusting your settings or designing a new pool from scratch, we’d love to hear from you. Our team can look at your garden and suggest what will work best.
Call us on 01483 323 676 or email hello@hilifepools.co.uk for a friendly, no-pressure chat, or get in touch online and we’ll come back to you.
