What is Chlorine Demand?

One of the leading causes of swimming pool water problems is environmental contamination. This means anything applied to your property or home that is not labeled for use in swimming pools.

Ammonia, Nitrogen and Phosphate contamination of drinking water as well as pool water is a problem throughout the country. Rainwater alone will not cause a chemical problem. High levels of Nitrogen ammonia compounds entering the water will. The chlorine that was in the pool is used up in the process of destroying the nitrogen ammonia compounds. Any remaining ammonia compounds are now causing a chlorine demand. Since algae is always present in pool water it will grow rapidly unless chlorine demand is treated.

High phosphates can also lead to chemical and algae problems. It will require maintaining higher chlorine residuals to maintain a pool with a high phosphate level. Maintaining the pool during the winter is also made more difficult if high levels of phosphates exist.

There are Two Ways these Products Enter your Pool

The first is direct application meaning it was broadcast with a spreader or sprayed. With liquid applications there is very little control. The slightest breeze can cause the product being sprayed to drift and contaminate the pool. The question is what type of product is being applied, in what amount and in what concentration? These factors will determine how much of a chemical problem then occurs.

The second means of contamination is from runoff. Generally with hard rains 85-90% of pools will have some type of runoff, whether it comes out of the yard, landscaping, or even the flower pots sitting on the deck. If any of these areas have been treated with any product within 3 to 4 weeks, it is likely there will be chemical problems.

Products that Cause Problems

There are many products that have been documented to cause major chemical problems in swimming pools. You can be assured that any product for yards, flowers, plants or trees, applied in liquid or granular form will cause chemicals problems if they are allowed to enter the pool.

Besides causing chemical problems these products have toxicity levels that may cause pool water to be unsafe. High levels of some compounds such as nitrates and nitrites can affect young children and older adults.

Items such as herbicides, fertilizers, bug sprays, window and deck cleaners, will all affect your pool water in some way. We understand everyone wants a green weed-free yard, beautiful flowers, plants and trees. Keep in mind that anything entering your pool water will affect it in some way. Besides the additional chemical cost and inconveniences there are other concerns such as the possible health hazards it poses to anyone swimming in your pool.

If your yard company tells you their product won’t affect the pool we suggest you ask for the MSDS sheet on the product they are applying and forward it to your service company.

Natural occurring organics like pollen and green matter (i.e. leaves, grass, flowers) can add to phosphate levels which can create chlorine demand by locking up the chloramines as well as increase the phosphates in your pool.

Treating High Chlorine Demand

The only way to treat the pool is either through partial drains and introducing fresh water or treating with large amounts of shock which is determined by a high chlorine demand lab test.

You can stop by Professional Pool & Spa and have your water tested at anytime. As of March 1, 2023 we will be charging $15 to run a demand test.