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Healthy pool water is simpler than it looks
Walk into any pool supplies shop and the shelves can feel a bit overwhelming. Tubs, bottles, tablets and granules, all with long names and bold warnings. It’s no wonder many new owners worry they’ll get it wrong.
Here’s the good news. Most pools only need a handful of pool chemicals to stay clean, clear and comfortable. Once you understand what each one does, the whole thing starts to make sense.
In this guide we’ll explain the main products in plain English. We’ll cover what they’re for, how to use them safely and how to tell when something’s out of balance. We’ll also look at ways to reduce how much you need to add.
Why water care matters
Pool water is shared by everyone who swims in it. Sweat, sun cream, leaves and rain all bring in things that need dealing with. Good water care keeps swimmers comfortable, protects your pool and equipment, and stops small problems growing into big ones.
Pool chemicals fall into a few simple groups
It helps to think of your products in groups, based on the job they do. Most pools need something from the first two groups, and occasionally something from the others.
- Sanitisers kill bacteria and other germs.
- Balancers keep the water comfortable and stop it damaging surfaces.
- Shock treatments give the water a deep clean when it needs it.
- Helpers such as clarifiers and algaecides tackle specific problems.
Let’s look at each group in turn.
A good test kit comes first
Before you add anything, you need to know what the water actually needs. A reliable test kit is the most useful thing you can buy. Test strips are quick and handy for everyday checks. Liquid drop kits are more accurate. Digital testers take the guesswork out of reading colours. Whatever you choose, keep it out of direct sunlight and replace reagents before they expire. Guessing is the fastest way to waste money on pool chemicals you didn’t need, or to throw the water out of balance.
Sanitisers keep the water safe to swim in
The sanitiser is the most important product in your pool. Its job is to kill bacteria and other germs brought in by swimmers and the environment.
Chlorine
Chlorine is the most common sanitiser in UK pools. It comes in a few forms:
- Tablets that dissolve slowly in a floating dispenser or feeder
- Granules that dissolve quickly and are handy for top-ups
- Liquid chlorine, which works fast and is often used in larger pools
Some chlorine products contain a stabiliser that protects it from sunlight. This is helpful outdoors, but stabiliser can build up over time, so it’s worth testing for it now and then.
Salt systems
A salt system adds a small amount of salt to the water. A unit on the pipework turns it into chlorine as the water passes through. You still have chlorine in the pool, but it’s made on site, so you’re handling far fewer tubs. Many people find the water feels softer. Our guide to choosing a saltwater pool explains more.
Other options
Some pools use bromine, which is popular in spas and hot tubs because it stays stable in warm water. There are also other sanitising systems out there. Talk to us about what would suit your pool.
Spas and swim spas need a little extra attention. The water is warmer and there’s much less of it, so a few bathers can change the readings quickly. Testing more often, and following the guidance for your model, keeps the water fresh and inviting.
The right level
Most guidance suggests keeping free chlorine at a low, steady level, often somewhere around 1 to 3 parts per million for home pools. Always check the guidance for your pool and sanitising system, as it can vary.
Why sanitiser levels drop
Sanitiser gets used up as it works. Sunshine breaks it down, warm water speeds up the process and every swimmer adds more for it to deal with. That’s why levels can fall quickly on a hot, busy weekend. Regular testing lets you top up before the water starts to suffer.
Balancing products protect your pool and your swimmers
Sanitiser does the cleaning, but it only works properly when the water is balanced. These are the readings to keep an eye on.
pH
pH shows how acidic or alkaline the water is. Most pools aim for around 7.2 to 7.6. If pH is too high, chlorine works less well and water can turn cloudy. If it’s too low, water can become corrosive and sting the eyes. You’ll use a pH reducer or pH increaser to adjust it. Our guide to pool pH goes into more detail.
Total alkalinity
Alkalinity acts like a buffer, stopping pH from swinging about. A common target is around 80 to 120 parts per million. You’ll usually raise it with an alkalinity increaser and lower it with the same acid products used for pH.
Calcium hardness
This measures how much calcium is dissolved in the water. Too little can make water aggressive towards surfaces. Too much can cause scale and cloudiness. In the hard water areas of the South East, it’s more often too high than too low.
Adjust things in the right order
When several readings are out, it helps to follow a simple order. Correct alkalinity first, because it affects pH. Then adjust pH. Once both are in range, bring your sanitiser up to the right level. Make one change at a time, let the water circulate for a few hours and retest before moving on. Small, steady steps work far better than big doses.
Shock treatments and helpers have their place
Most of the time, sanitiser and balancers are all you’ll need. Now and then, though, the water needs a little extra help. These occasional pool chemicals are useful to keep on the shelf.
Shock treatment
A shock is a larger dose of oxidiser that breaks down contaminants and gives the water a reset. You might shock after heavy use, a hot spell, a storm or if the water starts to smell stale. Some shocks are chlorine based. Others are non-chlorine and let you swim again sooner. Always follow the label for timing.
Clarifiers and flocculants
These help your filter deal with fine particles that make water hazy. Clarifiers clump particles together so the filter can catch them. Flocculants make them sink so you can vacuum them out. Our guide to cloudy pool water explains how to use them.
Algaecides
An algaecide can help prevent or treat algae growth. It works best alongside good sanitiser levels, not instead of them. Some owners add a small maintenance dose through the warmer months, when algae grows fastest. If you do spot green, black or mustard patches, brushing and a proper treatment plan will be needed.
Handle pool chemicals safely every time
These products are safe when used properly, but they deserve real respect. Please follow these rules without exception.
- Read and follow the label. It tells you how much to use and how to add it.
- Wear protection. Use chemical-resistant gloves and eye protection.
- Never mix chemicals. Not in the pool, not in a bucket and not on a scoop. Some combinations can react dangerously.
- Add chemical to water, never water to chemical. Pour the product into a bucket of water, not the other way round.
- Add one product at a time. Let the water circulate and retest before adding the next.
- Keep swimmers out until the water has circulated and your readings are back in range.
- Store them properly. Keep products in their original containers, somewhere cool, dry and well ventilated, and well away from children and pets.
Spotting too much chlorine
It’s easier to overdo chlorine than many people think. Signs that levels may be too high include:
- A strong chemical smell around the pool
- Red, stinging eyes or itchy, dry skin after swimming
- Swimwear fading faster than usual
- A test reading well above your target
Interestingly, a strong “chlorine smell” can also mean the opposite. It’s often caused by used-up chlorine combining with sweat and other waste. So always test rather than guessing.
Bringing chlorine down
If levels are too high, stop adding chlorine and leave the cover off in the sunshine. Levels usually fall naturally over a day or two. Running the pump helps, and a partial drain and refill can speed things up. Keep swimmers out until your test shows the level is back in range.
You can reduce how many pool chemicals you need
Nobody wants to add more to their water than they have to. A few smart choices can cut down how much you use.
Good filtration and circulation
A well sized filter and pump, run for the right hours, removes much of the dirt that sanitiser would otherwise have to deal with.
A cover
A cover keeps out leaves, dust and rain, and shields the water from sunlight, which breaks down chlorine. It also helps keep heat in. Putting it back on after every swim soon becomes second nature, and your water will be in better shape each time you lift it off.
UV and other secondary systems
Some pools use an ultraviolet unit on the pipework. As water passes through, the UV light helps neutralise bacteria and other organisms, including some that chlorine struggles with. You still need a small amount of sanitiser in the pool, but the overall amount can often be lower. Talk to us about whether a system like this would suit your pool.
Clean swimmers
A quick shower before swimming washes away sun cream, lotion and sweat. It’s one of the simplest ways to keep the water fresher. Our guide to getting your pool ready for summer covers this in more detail.
A simple weekly routine
A regular rhythm means you’ll use fewer pool chemicals overall, because problems are caught early. Here’s a routine that works for many owners in the swimming season:
- Test sanitiser and pH two or three times a week.
- Test alkalinity once a week, and calcium hardness once a month.
- Skim the surface and empty the baskets.
- Brush the walls and floor, and vacuum if needed.
- Check the filter pressure and clean or backwash when it rises.
- Keep a simple log of your readings and what you added.
A pool that’s easy to keep clean
The pool’s surface plays a part too. Our one-piece pools have smooth, non-porous finishes, which give algae and dirt less to cling to. You can explore our full range of pools to learn more. For more ideas, take a look at our article on natural swimming pools.
Water care questions we get asked a lot
How often should I test my pool water?
During the swimming season, checking sanitiser and pH two or three times a week is a good habit. Test more often after heavy use or bad weather.
Can I swim straight after adding chemicals?
It depends on the product. Always check the label, let the water circulate and retest before anyone swims.
Why does my pool smell of chlorine?
A strong smell often means used-up chlorine rather than too much. Test the water, and a shock treatment may help.
What’s the best way to store chemicals?
Keep them in their original containers, in a cool, dry and ventilated place, away from children and pets. Keep different products apart.
Do salt pools still need chemicals?
Yes. The salt system makes chlorine for you, but you’ll still need to test and balance pH and alkalinity.
Can someone else look after my water for me?
Of course. We offer aftercare and servicing, and we can help you set up a simple routine you’re comfortable with.
Get friendly advice on pool chemicals
Looking after your water gets easier with every week that passes. With a good test kit, a few core products and some sensible habits, you’ll soon feel confident.
If you’d like help, whether that’s a one-off check or regular aftercare, our team is always glad to hear from you.
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.
