What Causes High TDS in Pools?

As a pool owner, maintaining a pristine and enjoyable swimming environment for family and friends can often feel like a guessing game. Many common pool problems share similar symptoms, making it challenging to pinpoint the exact issue. One critical dilemma that often goes overlooked is high Total Dissolved Solids (TDS) levels. In this post, we’ll explore what TDS is, how it affects your pool’s health, and why draining and refilling it is necessary.

What is TDS?

Total Dissolved Solids, commonly called TDS, measure all dissolved solids and materials in your pool water. This includes routine chemicals, shock treatments, minerals, salts, and microscopic contaminants. The main culprit behind high TDS levels is evaporation. Fresh water evaporates from the pool daily, leaving behind all its minerals and solids. When we refill the pool with tap water, even more TDS is added, contributing to the accumulation of dissolved substances. Over time, TDS levels will naturally increase until they reach a point where they become problematic.

While TDS levels are generally not problematic in moderation, neglecting to monitor them can lead to complications. It’s essential to understand how TDS impacts your pool and what you can do to manage those levels effectively.

When is TDS Too High?

TDS levels above 1,700 ppm of tap water are considered “too high.” This threshold is significant because elevated TDS can hinder the effectiveness of your pool chemicals, lead to cloudy water, and create an environment conducive to algae growth and other unwanted contaminants.

Signs of High TDS Levels

• If you notice any of the following symptoms, it might be time to check your TDS levels:
• Difficulty maintaining water chemistry balance
• Faulty test readings for other aspects of water balance
• Salty-tasting water
• Scale buildup (if calcium hardness levels are also high)
• Skin and eye irritation
• Algae growth despite adequate sanitizer levels
• Cloudy or discolored water
• Metal corrosion (if TDS exceeds 5,000 ppm)

Problems Associated with High TDS

1. Chemical Imbalance: High TDS levels can make it challenging to balance your pool’s chemistry. As solids accumulate, the water becomes saturated and can’t properly absorb new chemicals. This process reduces the effectiveness of Free Available Chlorine, leading to unsanitized water and increased risks of algae growth.
2. Corrosion and Scaling: Elevated TDS can cause scaling on pool surfaces, clogging filters, and plumbing systems. It can also lead to corrosion of metal fixtures, such as ladders and lights, resulting in costly repairs.
3. Unpleasant Swimming Experience: Elevated TDS can lead to water that feels slimy or irritating to the skin and eyes. If your pool is uncomfortable, it defeats the purpose of having one in the first place!

How to Test for Total Dissolved Solids

Standard test kits and strips used for measuring other elements of water chemistry typically do not test for TDS. Instead, you need a TDS meter to obtain an accurate reading. These meters measure the electrical conductivity of your pool water, indicating the volume of dissolved solids. While they don’t specify which solids are present, they do reveal if levels exceed acceptable amounts. Our technicians use professional-grade testing equipment that is routinely calibrated. Contact our office for your most recent readings.

The Solution: Drain and Refill

The most effective way to manage high TDS levels is to drain and refill your pool. Here’s why:

• Immediate Reduction: Draining your pool eliminates a significant portion of the dissolved solids, bringing TDS levels back to a manageable range.
• Chemical Reset: A freshwater fill allows you to start anew with your chemical balance, ensuring your sanitizers work effectively.
• Enhanced Enjoyment: Refilling your pool results in clearer, cleaner water, leading to a more enjoyable swimming experience.

How to Reduce Total Dissolved Solids

To lower TDS levels effectively, the best method is to drain your pool and refill it with fresh water. Our technicians will first treat the water as safe and then use submersible pumps to drain the water to sewer waste. Draining the water entirely is the best way to ensure there are no residual contaminants in the water. Once drained, we recommend starting a refill as soon as possible. Our recommendation is to prevent any plaster issues within 24-48 hours. We also recommend cleaning the pool filter before adding the initial chemicals to start the pool up again. This will ensure proper mixing and that nothing from the filter will contaminate the new water.