Swimming pool water and illness
People might get ill from pool water if the water is contaminated by germs. The most common pool germs include bacteria (Giardia, E. coli, Legionella and Shigella), viruses (enteroviruses) and parasites (Cryptosporidium).
Chemicals are used to treat and control germ levels in pools so the germs don’t make you sick. But sometimes, particularly if the pool is very busy or poorly treated, the chemicals can’t act quickly enough and the germs can multiply.
Bacteria and viruses in pool water can cause illnesses including ear infections, eye infections and throat and chest infections, as well as gastroenteritis or diarrhoea (runny poo). The virus that causes hepatitis A can also be in pool water. Very rarely, the amoebae that cause amoebic meningitis might be in warm and hot water pools (where they thrive).
Eye and skin irritation can also be a problem if the pH of the pool water is too high or too low.
In this article, ‘swimming pools’ can mean public or private swimming pools, hydrotherapy pools, hot tubs and spas, inflatable and wading pools, and water parks.
How does pool water get contaminated?
Pool water can be contaminated by:
- skin, sweat, urine (wee), faeces (poo), saliva and open sores
- dirt, food and other solids that end up in the pool.
Germs can get into pool water quite easily. If a person who has diarrhoea goes swimming, germs can still be on that person’s skin, even if they’ve cleaned their bottom and hands really well.
Babies or non-toilet trained children who have runny poo are very likely to poo in the water if they’re taken swimming. Even if a sick child doesn’t go in the water, but the parent changes the baby’s nappy near the pool, the germs could still get in the water.
Keeping pools clean
If a pool has been properly treated, most germs in the pool will be killed by the pool chemicals.
Enough germ-killing chemicals need to be added to the pool so that the pH will
be at the right level to allow the disinfectant to kill germs without
it irritating people’s skin and eyes. If a pool has a strong chemical
smell, there is too much disinfectant. This might lead to skin and
It does take a while for pool chemicals to work. Viruses can take longer to kill than bacteria. If there are solids such as leaves in the water, it’s harder for the pool chemicals to do their job. One type of parasite, Cryptosporidium, is quite hard to kill and can even stay infectious for up to six days in pool water.
Also, when a pool is very busy – such as on a hot summer day – germs can get into even the cleanest pool. More people mean more germs and more dirt in the water.
Pool operators and staff are expected to test the level of pool chemicals regularly and treat the water appropriately if it gets contaminated.
For example, if there’s a poo accident, everybody has to get out of the pool. No-one can get back in until the pool staff have finished cleaning and disinfecting the pool. This usually involves scooping the poo out with a fine mesh scoop or bucket and getting rid of it in a sanitary way. The scoop is also cleaned and disinfected.
If you want to know how clean and safe a pool is to use when it’s really busy, ask the pool staff about the latest pH measurement. They should be able to explain it to you.
Wading pools in public and at home
Because wading pools are warm, shallow and mostly used by babies and young children, they’re the pools most likely to have germs that come from poo. Young children are also more likely to swallow pool water than other swimmers, increasing their risk of getting sick.
At a public pool, the wading pool will be treated with chemicals to try to kill the germs, but your home wading pool probably isn’t treated with pool chemicals. This makes it extra important to keep the water in the wading pool out of your child’s mouth.
Always empty the wading pool at home once you’ve finished using it. Leaving water in the wading pool is a drowning risk as well as a germ risk.
If there’s a poo accident in the wading pool, everyone must get out straight away. If you’re at a public pool, let the staff know immediately. If you’re at home, empty the water out, and give the pool a really good scrub with disinfectant. Rinse the pool before you refill it. If you’re at home and the accident is because of diarrhoea, you’ll need to dry the pool in the sun for at least four hours after you’ve cleaned it.
Healthy pool use
To help keep swimming fun and germ free for everyone, you can follow some simple tips.
For all swimmers
- Don’t get in the pool if you have, or have just gotten over, diarrhoea.
- Try not to get water in your mouth, and definitely don’t swallow pool water.
- Wash your hands with soap and water after using the toilet or changing a nappy.
- Shower before you get in the pool.
- You can check the pH of the swimming pool using store-bought pool test strips or by asking the pool staff for the latest inspection score.
For parents of young children
- Make sure your child has a clean bottom before getting into the pool.
- If your child is still in nappies, change the nappy regularly to stop the nappy’s contents getting into the water.
- Use swim nappies to help prevent solids from entering the water, but note that these aren’t leak proof. They can delay, but not stop, the germs from getting into the water.
- Try to prevent toilet accidents in the pool by making sure your child has regular toilet visits.
- Keep nappy changes away from the pool area. With lots of water splashing about, it’s easy for germs to end up in the pool.
- It’s recommended that children under 16 years should stay out of the spa. The germ risk from spas is too great for young immune systems. Also, children can’t regulate their body temperature as well as older people. This means they shouldn’t be exposed to the extremes of water temperature that you might get from the hot water in a spa.
For water safety
- You should be with young children and watching them at all times around water. You should have children under the age of five years within arm’s reach. You should be able to see children under 10 years at all times.
- Life jackets should be used rather than inflatable swimming aids.
Be sunsmart. Apply sunscreen to clean, dry skin 20 minutes before going outside. Reapply every two hours.