When and How Often to Shock a Hot Tub

Maintaining a hot tub can be pretty confusing at times. You want to keep your hot tub sanitized, but at the same time, you don’t want to use chemicals unnecessarily. So what does a safe shocking schedule look like?

For general use, you should add a chlorine-based shock to your hot tub water once a week. However, it’s good practice to use chlorine shock immediately after very heavy use. Non-chlorine shock helps your sanitizer to disinfect more effectively and should be used several times per week or after each use.

Both non-chlorine and chlorine-based shock play an important role alongside your sanitizer, so understanding how they work together is key.

This article is also going to show you:

  • Telltale signs your hot tub needs shocking
  • Whether shock is really necessary after filling
  • How long to wait after adding shocking
  • If it’s possible to add too much shock

When to use chlorine shock

Chlorine shock is used to keep your hot tub water clean and sanitary. It is also used to clear cloudy or smelly water and to kill bacteria and algae. The shock carries out these functions by removing chloramines, bromamines, and organic contaminants from your spa.

Furthermore, chlorine shock raises the chlorine level in your hot tub. This is necessary for reactivating the weakened sanitizers in the hot tub. 

If you use bromine for your spa, a chlorine shock can also help reactivate the bromide ions and convert them to hypobromous acid, which is the killing form of bromine.

Weekly maintenance

You should add chlorine shock to your hot tub at least once a week during warmer months. During winter, you should add the shock once every two weeks if you don’t get to use the spa as much as you do in the summer.

Carrying out weekly maintenance will help maintain correct sanitization levels and reduce impurities. If your hot tub hasn’t been used for an extended period of time, it’s important to shock it a full day before you intend to you it.

After heavy use

Ideally, you want to shock your hot tub water after heavy usage. When many people use your hot tub simultaneously, they pollute the water with oils, moisturizers, lotions, deodorant, sweat, and dead skin cells. 

These pollutants mix with the sanitizers in the spa water and form chloramine or combined chlorine. You can break down these contaminants by adding chlorine shock to the spa water.

Warning signs your hot tub needs to be shocked (and drained)

Smelly Water

Your hot tub water may look clean and clear. But if it smells funky, there may be bacteria lurking in the water. You can use your test strips to diagnose the problem.

Chemical Scent

A chemical scent indicates a buildup of the sanitizer in the water. More specifically, this smell is from the chloramines in the water. 

Cloudy Water

If your hot tub water is cloudy, check your filter. The problem could be a loose filter. Alternatively, you may need to replace or clean the filter.

Your water feels oily and greasy

Oily and greasy water is formed when bodily residue and body products like oils, soap, dead skin cells, hairs, and lotions contaminate your spa water. This usually causes a layer of scum to form on the water surface.

Your water feels slippery, slimy, or sticky

Slippery, slimy, or sticky water indicates that biofilm, mold, mildew, or algae may be present in the spa. You can fix this issue by adjusting the pH, shocking the water, and flushing the plumbing. To ensure complete eradication, drain the spa after shocking it.

Your water feels rough, gritty, or sandpaper-like

The major cause of rough, gritty, or sandpaper-like water is scale buildup. Scale occurs when water that is rich in minerals like calcium is heated. 

You can fix this issue by adjusting the alkalinity and pH levels. If the scale is fresh, you can use a soft rag or nylon brush to remove it. If it is more firmly deposited, you may need to drain the water and scrub the hot tub shell with a cleaner.

When to use non-chlorine shock

Non-chlorine shock is also known as MPS (Potassium Monopersulfate). It should be used after adding the first dose of shock to a freshly filled hot tub. 

It should also be used daily or after each hot tub session since it’s not as concentrated as chlorine shock and will dissipate in a few minutes.

Non-chlorine shock is a powerful oxidizing agent that improves sanitizer efficiency by freeing up chlorine to kill bacteria. 

It eliminates contaminants like oils, leaves, lotions, detergents, or dead skin cells. This helps reduce or prevent foaming and reduces strain on the hot tub filters. It also reduces the need to use chemicals that should be used sparingly.

Like chlorine shock, MPS also helps to break down chloramines and reactivate bromine in your hot tub. Additionally, since non-chlorine shock frees up chlorine, it reduces the need to super chlorinate your spa water.

Should you shock a hot tub after refilling?

A hot tub should not be shocked after refilling as the purpose of shock is to reactivate the sanitizer. When you fill your hot tub with fresh water, you expect that the water is mostly clean and free of contaminants.

Since there are no contaminants in the water, then there is nothing to prevent the sanitizers from doing their job. And if nothing is stopping the sanitizers from doing their job, then there is no need to add shock.

However, after some time or after heavy usage, the spa may contain contaminants and require shocking. Therefore, after refilling your hot tub, you should first add sanitizers and wait until they lose effectiveness before shocking the spa.

How long to wait after shocking a hot tub

Chlorine shock

If you use chlorine shock in your hot tub, you’ll have to wait around 24 hours before you can use the spa. This gives the chlorine enough time to work and allows the levels to drop to safe levels between 1-3ppm.

However, if you’ve added excess chlorine, you’ll need to wait for 48 hours for the chlorine to drop to safe levels. Ensure you test the water before entering.

It is important you wait for the chlorine levels to drop because high chlorine levels can cause severe health problems like cancer, skin irritation, eye irritation, nasal irritation, nausea, vomiting, and coughing.

Over shocking can also lead to high chlorine levels, which will not only harm your health but will also damage your hot tub. 

Non-chlorine shock

After adding non-chlorine shock to your hot tub, you only need to wait 15-20 minutes before entering the tub. 

This is because non-chlorine shock doesn’t contain chlorine, making it safe to soak in the hot tub water after a short while. Still, ensure you test the water before using the hot tub. 

Can you add too much shock?

It is possible to accidentally add too much shock to a hot tub. Adding a high dose of chlorine shock can damage both your health and the spa.

Excess chlorine levels can cause respiratory problems such as oxidative injury and inflammation. They can also cause your chest muscles to contract, leading to pain. 

Additionally, excess chlorine can form carcinogen chloroform and other harmful chemicals. If these toxic chemicals are inhaled or absorbed through the skin, they can cause health issues like miscarriages, birth defects, and even death.

The damage caused by excess chlorine is quite significant. It can cause your hot tub shell to discolor, become brittle, and crack.

It may also damage the fabric of the pillows in the spa, causing them to fade and become brittle. Excess chlorine can also damage your spa cover as well as the pipes and plumbing of your hot tub.

Joshua Milton

Joshua Milton is a seasoned hot tub enthusiast. With many years of experience in the industry, he offers valuable insights on hot tub maintenance, health benefits, and relaxation techniques.

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