Boiler water conductivity is caused by the amount of total dissolved solids (TDS) present in the water. Certain solids are more conductive than others. You will want to keep your conductivity levels within a “normal” range to prevent maintenance issues in the boiler.
Testing Boilers with Conductivity Probes
Install a conductivity probe to measure your feed water or boiler process water. You should install it to measure the feedwater and process water. There are two main types of boiler conductivity probes, contacting and non-contacting (toroidal).
Contacting probes- It is recommended to use this for pure water, with low amounts of TDS. Sensors with electrodes will produce a current. An analyzer will measure the ionic current (ions present in the water from dissolved solids). Usually, these will have 2 or 4 sensors.
Non-contracting, toroidal probes- These are recommended for hard water (lots of TDS) that is corrosive or scaling. While these sensors work in a similar way to measure currents in the water, the metal sensors are wrapped with plastic to prevent corrosion/damage.
Normal Range of Conductivity
For a low to medium-pressure boiler, 3500-4500PPM is an optimal range. As pressure increases, the amount of conductivity present in the boiler needs to decrease. This is why high-pressure boilers require significantly less conductivity. Your boiler manufacturer should specify the recommended ranges of conductivity; this information should be paired with your region’s water hardness.
Common High Conductivity Issues
Scale- High conductivity means there is a large amount of TDS. Many of these TDS, such as calcium carbonate, lead to scale deposits. These scale deposits will build up on your boiler’s water lines and heat transfer surfaces and decrease the efficiency of your boiler significantly.
Corrosion- TDS that cause corrosion, along with oxygen, are byproducts of high conductivity. As aforementioned, it is important to use toroidal probes when dealing with highly corrosive water, as contacting probes will rust and become ineffective.
Reduce Water Conductivity in Boilers
Now that we have established the issues caused by boiler water conductivity and the recommended ranges, how do you reduce the amount of conductivity present in the water?
Top/bottom blowdowns. Essentially, you are removing solids from the water. Top blowdowns (skimming) involve removing TDS present at the boiler’s surface. Bottom blowdowns (flushing) sunken TDS. Another benefit of blowdowns is the removal of sludge that can accumulate over time.
Adjust chemical treatment and water softening. The treatment and pre-treatment you do on boiler water will impact its conductivity. Softening chemicals will reduce conductivity, while acids increase it.
Automated controls will work with your conductivity probes to fix your conductivity without manual intervention.
Water Softeners INCREASE Conductivity
Since total dissolved solids and conductivity are related, you may think that removing solids with water softeners will solve this problem. Water softeners do remove the “hard” dissolved solids associated with scaling. However, they also introduce a new TDS, salt. Salt leads to higher levels of corrosion. Salt will increase the amount of conductivity, and if you use a water softener, it is necessary to utilize corrosion inhibitors.
Boiler Chemistry Experts
Chardon Labs has perfected boiler conductivity adjusting as part of our boiler treatment. Our company is entirely focused on the treatment and testing of commercial heating and cooling equipment. This has allowed us to hone our expertise. We provide regular reporting that shows boiler conductivity, along with other important data of your boiler. For help or questions, please leave a quick message, and an expert will be in touch!
Matt Welsh
Matt Welsh is the Vice President and Water Consultant at Chardon Labs. He helps consult a wide range of customers utilizing various methods of water treatment, from chemical to chemical-free approaches, large and small applications, and across a wide range of geographical influences. With 20 years of water treatment experience, including a wide range of troubleshooting and service in potable water and non-potable HVAC and industrial applications, he is an expert in water treatment chemistry for cooling towers, boilers, and closed-loop systems.
