When Is a Pool Unsafe to Swim In? What You Should Know

When Is a Pool Unsafe to Swim In

When you are a new pool owner, you may be overwhelmed at how much maintenance a swimming pool needs in order for it to be safe to swim in.

Even after routinely cleaning it and adding chemicals in, a question you may have is: how quickly will it become unclean again?

Sometimes the answer is very obvious. If you can visibly see that the water is a strange color, or physically feel that the water feels different (i.e. it is slimy or irritating your skin), then that is a clear sign something is off.

However, sometimes water can look clean but be filled with pathogens. Or you may have just finished adding in a lot of chemicals into the pool and aren’t sure when it’s safe to swim in again.

In this article, I will go over the ways you can easily tell if your pool is safe to swim in and how you can find out without touching it or experiencing any side effects.

Times when a pool is unsafe to swim in

The water is anything but blue and clear

While visually checking for strange pool water colors isn’t a foolproof approach, it is a point of reference you can use in tandem with other checks to determine if a pool is safe or not.

A common problem pool owners encounter is seeing that their pool is a little bit green. That means that there is an algae problem, and with algae comes plenty of bacteria.

If a pool has been neglected for a long time, you may notice that the water has turned red, brown, or even black. These are all signs of various types of algae growth, but it could also be caused by dirt, leaves, or even dead animals.

Some other visual indications of a problem with the pool water are: cloudy or murky water, a dull blue appearance that obscures the bottom of the pool, or an awful odor.

The pool water feels slimy

You can physically tell the difference between a clean pool and one that is unclean. If you put your hand in the water and it feels slimy, for instance, then that should be a red flag that something is wrong.

In this case, it probably means the chlorine isn’t working and that it is time to shock the pool. This means adding a high concentration of chlorine in a short period of time to kill all the bacteria and pathogens in the water. You would do the same thing if your pool was green or yellow due to algae growth.

The filter is clogged

The pool filter plays a crucial role in removing debris from your pool. However, if you are not clearing the filter from time to time, then debris can start to clog it up.

If you notice that water is not coming from the circulation jets in your pool, then that is a clear sign that the filter is clogged and that you need to unclog it ASAP.

A clogged filter can also overstress the pool pump which circulates the water, resulting in a breakdown of another equally important piece of pool equipment.

Also as a general rule, if a piece of pool equipment is not in operation or appears to be damaged, then definitely do not swim in that pool.

There is a strong “chlorine” smell

Contrary to popular belief, the “chlorine” smell is not actually chlorine, but the smell of chloramine. Furthermore, a strong chloramine smell is not a sign of a strong pool, but one with weak chlorine levels.

Allow me to explain. When chlorine is used up, it produces a byproduct called chloramine. Chlorine is used up whenever it reacts with nearly everything, from urine to algae to lotion and basically anything that gets into the pool.

Thus, the strong chlorine smell just means that much of your chlorine has been used up because there is the presence of a lot of chloramine.

Too soon after shocking the pool

There are times when a pool visibly looks safe to swim in but isn’t. One such example is after shocking the pool.

Once again, shocking the pool means adding an extremely high concentration of chlorine into the water in a short period of time.

Even though chlorine is our disinfectant, prolonged or significant exposure to it can lead to many side effects like asthma, rashes, red eyes, dry skin and hair, itchiness, and so on.

It’s generally recommended you wait at least 24 hours after shocking the pool before it’s safe to swim in.

To be safe, you can use a pool test kit to see if the free chlorine level has reached 3 ppm or less.

When the pH is not balanced and total alkalinity is low

When using a pool test kit, some other numbers you need to look out for are the pool’s pH and alkalinity. Specifically, the pH should be around 7.4-7.6, and the alkalinity should be around 80-120 ppm.

Maintaining both of these values is crucial to ensure the water remains sanitized and non-corrosive. If your testing kit does not read these values, your pool may be unsafe to swim in.

The pH scale measures how acidic or basic your pool water is. At 7.4-7.6, that actually means it is slightly basic (pH of 7 is neutral, numbers higher than that are basic, numbers lower than that are acidic).

Total alkalinity can help stabilize pH levels so that it remains in that ideal range. The lower the total alkalinity, the more wildly the pH can swing up or down.

The pool water’s pH not only affects how effective the sanitizing ability of chlorine is, but if it becomes acidic it can corrode the pool equipment.

If your pool water has a pH of 8.0, chlorine will only be 20% effective at sanitizing contaminants in the water. If the pH is at 7.0, then the free chlorine is only 66% effective.

As you can see, a pool test kit is crucial in determining whether or not the water is safe to swim in even if it is not visibly obvious anything is wrong. You always need to have one on hand to test your pool water frequently so that you can manage the water chemistry as needed.

No lifeguard, swimming buddy, or adult supervision

This mostly applies to public pools, but can also apply to backyard pools as well. If you are ever swimming without someone watching your back, then you are at the greatest risk of drowning should a problem arise.

Even if a public pool has a lifeguard, that lifeguard is watching over many people. They may miss something if the pool is too crowded. Multiple lifeguards need to be on duty at public pools.

For backyard pools, especially with kids, an adult should always be present to supervise.

Any activity is more fun with at least one other person, and when it comes to swimming, it can also increase safety. Your swimming buddy can call for help or rescue you themselves should anything go wrong.

Too many people in the pool

This point applies to both public and backyard pools. An overcrowded pool makes it harder for lifeguards/an adult to spot someone in distress.

Limited space also can lead to accidentally colliding with somebody and is a safety risk for somebody submerging underwater if they are having trouble surfacing.

There is also the risk of waterborne diseases spreading. As much as we like to think that people have decent hygiene, there are sure to be some people who introduce a lot of pathogens to the pool.

We don’t know for sure if chlorine is able to eliminate all of the bacteria and pathogens in the water if there are too many people, so in many ways, it is unsafe to swim in a crowded pool.

Photo Credit: vanou (CC BY-NC-ND 2.0)