Why will my pool not hold chlorine?

Author: Jan Turner  |  Last update: Friday, October 10, 2025

Algae, bacteria, or fungus growth. Debris or contaminants from winter or periods of inactivity. Heavy pool usage or high bather load, especially during summer. Biofilm or organic material in the water, such as sunscreen, leaves, or algae.

Why does my pool chlorine keep dropping?

  • Sunlight Exposure : UV rays from the sun can break down chlorine quickly.
  • High Bather Load : More swimmers mean more contaminants (like sweat, oils, and urine) that consume chlorine.
  • Organic Debris : Leaves, dirt, and other organic materials can deplete chlorine levels as they break down.

How do I get my pool to hold chlorine?

Maintaining Chlorine Levels Long-Term
  1. Maintain proper circulation: Ensure your pool pump runs for sufficient hours each day.
  2. Shock your pool regularly: Weekly shock during peak usage times is recommended.
  3. Use a chlorine stabilizer: If your CYA level is low, consider using a stabilizer like Trichloro tablets.

Why is my pool eating up chlorine?

Chlorine demand occurs when there are a lot of organic and inorganic chemicals, minerals and other types of matter in swimming pool water that the chlorine is struggling to neutralize.

Why is my pool not producing chlorine?

It can be one of two things, either your cell is not producing or you have what is called a chlorine demand although this is rare on pools with chlorine generators. Be sure that you were tested for phosphates. If phosphates are in pool water then the cells do not produce the chlorine needed.

Why Your Pool Isn't Holding Chlorine

Why can't I get chlorine to stay in my pool?

Debris or contaminants from winter or periods of inactivity. Heavy pool usage or high bather load, especially during summer. Biofilm or organic material in the water, such as sunscreen, leaves, or algae. Pool covers trapping chlorine and causing it to dissipate more rapidly.

How do I fix the chlorine demand in my pool?

To Eliminate Demand

Shock the pool with 3 lbs. of SuperSonic per 10,000 gallons of pool water. Circulate the water continuously.

What is killing the chlorine in my pool?

Bacteria, algae and microscopic contaminants, such as urine, sweat, sunscreen and beauty products, take a toll on your swimming pool's water chemistry. These substances, when present in your pool water, accelerate chlorine demand and can affect your chlorine's ability to maintain properly sanitized water.

What causes a chlorine lock in your pool?

Too much Stabilizer: A chlorine lock can occur when you have added too much cyanuric acid, or stabilizer, into your pool water. Stabilizer is a chemical intended to protect chlorine from burning off too quickly from UV rays. If you get too much of it, it can completely block your chlorine and make it ineffective.

Why is my pool not holding chlorine and cloudy?

There are a few possible causes for murky water, with the most common causes of a cloudy pool being a low runtime, chemical imbalance, algae, excess debris, and excess calcium. 1 Each problem has a diagnosis and treatment but generally should clear up in a few days with proper attention.

How do I stabilize my pool chlorine?

Make sure the pool is clean and chlorine is at the proper level. Read the dosage on the bottle for recommendations. For liquid or powder stabilizer, add to the pool by walking around the perimeter and slowly adding stabilizer along the edges. If using powder stabilizer, brush pool down to promote mixing.

Why do I have to add chlorine to my pool every day?

This powerful compound is the real bacteria-fighter, destroying the cell walls of harmful microorganisms and keeping your pool water sanitized.

Why is there no free chlorine in my pool after shocking?

If you just added chlorine or a chlorine-based shock to your pool and you still have a low chlorine level, there's a chlorine demand problem. In order to cure chlorine demand, triple shock your pool with calcium hypochlorite or cal-hypo shock.

How to raise chlorine level in pool quickly?

Raising pool chlorine can be much easier than trying to lower chlorine levels. Simply adding chlorine in the form of chlorine tablets, granular chlorine, liquid shock or powder shock will increase the total amount of chlorine within the pool.

Is it OK to go in a pool with low chlorine?

Surely it's safe to swim in. FALSE. It doesn't matter how much time and effort you put into skimming, brushing, vacuuming, circulating, and filtering your pool. If there's not enough chlorine in the water, your pool's not actually clean, and the water's not safe.

How long does chlorine stay high after shock?

Shocking is crucial for removing any pathogens in the water and making a pool safe for swimming. It also involves using heavy-duty chemicals, including chlorine, so it's best to wait at least 24 hours after you shock a pool to go swimming. Going in too soon can potentially cause skin, eye, and even lung problems.

Why is the chlorine disappearing from my pool?

The consistent inability to maintain chlorine levels is also called “chlorine demand” and is most often caused by a high level of inorganic and organic contaminants in the water. Those contaminants force the chlorine to work extremely hard to oxidize them, leaving little chlorine to protect swimmers.

How to fix a chlorine lock in a pool?

How to Break Chlorine Lock in Pools
  1. Partially Draining Your Pool. A partial drain where you drain a portion of the water and replace it with fresh water can often be the best option. ...
  2. Non-Chlorine Shock. Another effective solution can be a non-chlorine shock treatment. ...
  3. Chlorine Shock.

How do you control chlorine leakage?

If a leak develops in a chlorine system, shut off the cylinder valves and ventilate the area to the outdoors prior to repairing the leak. Should a major leak develop which can not be controlled, clear the area of personnel, and exhaust the fumes to the outdoors.

What eats up chlorine in a pool?

Direct sunlight (UV)

Direct sunlight breaks down chlorine.

How do you make pool chlorine last longer?

Skim your pool water at least once a day and vacuum the interior of your pool once a week to remove debris. This will give your chlorine less to keep clean, making it last longer than it would without maintenance.

Why does my chlorine keep dropping to zero after?

It could be chloramines, combined chlorine, high TDS, low cyanuric acid, unbalanced water, phosphates, or nitrites/nitrates. Water analysis will reveal the usual causes.

Why does my pool keep running out of chlorine?

Basic Checks First: Filter Run Time: Make sure your filter is running for at least 10 to 12 hours total per day, specifically during the daylight hours when the sun is out. Circulation: Check that you have strong circulation while on high speed.

Why is my pool pump not producing chlorine?

Low/No chlorine production

The factors that affect chlorine levels include the summer heat, poor filtration, bather load, and the frequency of use. It's also possible that the time period you set is too short, the chlorine output level is too low, or the filter needs backwashing.

Why is my pool chlorine shock not working?

Thankfully, by far the most common reason why pool shock wouldn't work is very straightforward. It's all to do with your pool's pH. Pool expert Rafi Friedman told me that 'Pool shock works best with a balanced pH. If your pool's pH is too high or too low, the shock won't be effective.

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