How Do I Lower Total Dissolved Solids (TDS) in My Pool

The only way to lower TDS is to partially drain the pool and refill it with fresh water.

What is Total Dissolved Solids (TDS)?

Total Dissolved Solids is a measurement of everything that is dissolved in your pool water. This can include:

• Salts (such as those used in saltwater pools)
  

• Chlorine byproducts
  

• Calcium
  

• Alkalinity
  

• Other minerals and metals
  

While some TDS components, like calcium and chlorine, are necessary to keep the pool water safe and sanitized, excessive amounts can lead to issues. High TDS levels can cause water to appear cloudy, reduce the effectiveness of pool chemicals, and even lead to scaling on pool equipment and surfaces. High TDS levels can also make it harder for your pool heater to efficiently warm the water.

How Do TDS Levels Get High?

There are several ways that TDS can build up in your pool over time:

• Evaporation: As water evaporates, the dissolved solids are left behind. This leads to gradual increases in TDS levels, especially in hot, dry climates.
  

• Frequent chemical use: Regularly adding chemicals to maintain water balance, like chlorine or algaecides, can introduce more dissolved solids into the water, contributing to higher TDS.
  

• Swimmer activity: Sweat, lotions, oils, and even urine from swimmers can add dissolved solids to your pool.
  

• Water source: If your pool is filled with hard water, it could be adding minerals like calcium and magnesium that increase TDS.
  

Common Signs of High TDS Levels

You may notice the following signs when your pool’s TDS is too high:

• Cloudy water that is difficult to clear
  

• Difficulty balancing pool chemicals, even after regular adjustments
  

• Scaling or calcium deposits on pool surfaces or equipment
  

• Reduced effectiveness of your pool’s sanitizer or chlorine
  

• Unpleasant water taste or odor
  

How to Lower Total Dissolved Solids (TDS) in Your Pool

The most effective way to lower TDS in your pool is through water replacement. While there are some methods that can help remove certain dissolved solids, draining and refilling the pool remains the most reliable option.

1. Partial Water Drain and Refill

One of the most effective ways to lower TDS levels is to partially drain your pool and refill it with fresh water. This method dilutes the dissolved solids and reduces their overall concentration in your pool water. Here’s how to do it:

• Step 1: Test your pool water using a TDS meter or have it tested at a pool store.
  

• Step 2: Drain a portion of the pool water, generally around 20-30%. This will help effectively lower the concentration of dissolved solids.
  

• Step 3: Refill the pool with fresh water and test again to ensure the TDS levels have decreased.
  

Pro Tip: If you’re still experiencing high TDS after one partial drain, you may need to repeat the process over time, especially if your pool is subject to regular chemical use or evaporation.

2. Reverse Osmosis (RO) Filtration

Reverse osmosis (RO) filtration is a more expensive but efficient method of reducing TDS in your pool. RO filtration uses a semi-permeable membrane to remove dissolved solids from the water, including salts, minerals, and metals. This method is highly effective at removing TDS without needing to drain the pool. However, it typically requires professional installation and can take a few hours to a few days depending on the size of your pool. RO filtration also helps preserve your pool’s chemical balance and reduces water waste.

3. Backwashing the Filter

While backwashing your pool filter won’t directly reduce TDS, it can help remove debris and particulates that contribute to the overall water quality. A clean filter will ensure the pool’s circulation system works efficiently, reducing buildup and allowing the system to function at optimal levels. Regular backwashing helps maintain water flow, but it is unlikely to significantly reduce TDS levels on its own.

4. Use a TDS Reducer

Some pool supply stores sell chemicals specifically designed to reduce TDS levels. These products work by breaking down salts and minerals, making them easier for your pool filter to remove. However, these chemicals are not as effective as water replacement or reverse osmosis and may not be suitable for all types of pools. If you decide to use a TDS-reducing chemical, always follow the manufacturer’s instructions carefully.

5. Maintain Proper Pool Chemistry

Regular maintenance and monitoring of your pool’s chemistry can help prevent TDS from building up excessively in the first place. By balancing chemicals and keeping the pool water in the ideal range, you can avoid issues with high TDS levels. Here’s what you need to monitor:

• pH levels: Keep your pool’s pH in the ideal range of 7.4-7.6 to ensure the best performance of your pool sanitizer.
  

• Calcium hardness: Regularly check calcium levels and adjust them to prevent scaling and the buildup of mineral deposits.
  

• Chlorine balance: Properly maintaining chlorine levels will help sanitize the pool without introducing excessive byproducts that contribute to TDS.
  

6. Install a Saltwater System Wisely

If you have a saltwater pool, it’s important to carefully manage the amount of salt added to the system. Saltwater pools are more prone to high TDS levels, especially if the system is over-salted. Make sure to follow the manufacturer’s guidelines on salt levels, and periodically test the TDS to ensure it stays within the desired range.

Preventing High TDS Levels in the Future

Once you’ve lowered the TDS in your pool, taking steps to prevent it from rising again is key to maintaining your pool’s water quality:

• Use a pool cover: A pool cover reduces water evaporation, which helps prevent TDS from building up.
  

• Limit chemical use: Avoid over-using chemicals like chlorine and algaecides, which contribute to TDS. Use only as needed.
  

• Encourage good swimmer hygiene: Have swimmers shower before entering the pool to reduce contaminants like sweat and oils that add dissolved solids to the water.

• Use soft water to fill your pool: If your area has hard water, consider using a water softener to lower mineral content before filling your pool.