Boiler TDS Systems

What is TDS?

As a boiler generates steam, impurities found within the boiler feed water do not evaporate and begin to concentrate in the boiler. As the concentration of these impurities (known as dissolved solids) increases further, it begins to affect the phase-change process of water into steam by increasing the stability of the bubbles at the (boiling) water-steam interface.

Depending on a boiler’s capacity (kg/hr) and operating pressure (barg), stable steam bubbles start to accumulate in the steam space within the boiler chamber. If untreated, these bubbles are carried forward into the steam main, causing the raised steam to be exceptionally wet and contain boiler water and suspended solids. This leads to the steam main and ancillaries – such as control valves, steam traps and flowmeters – being contaminated with impurities, which consequently affect their service life.

Whilst the formation of stable steam bubbles (also known as foaming) can be caused by high levels of contaminants produced by oils and fats, the most common cause of carryover is due to increases in the Total Dissolved Solids (TDS) levels in the boiler water. Assuming other contaminant sources are properly managed, careful monitoring and control of boiler water TDS levels would ensure that the risks of foaming and carryover are minimised.


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Product Variations/Accessories/Complementary (Product Features List/Benefits)

Valveforce can provide turnkey solutions, including:

  • Site surveys
  • Bespoke feed tank design and construction
  • Installation
  • Commissioning
  • Servicing/maintenance contract

Valveforce can also supply and install the following solutions and equipment:

  • Complete TDS System inclusive of:
    • Electric TDS Control valve with
    • TDS Controller - panel mounted
    • TDS Probe
    • Spool piece
    • Valves
    • Sample cooler
  • TDS Control Panels
    • With modulating controller for the TDS system
    • With Blowdown timer for bottom blowdown
    • Within Valveforce designed control panels
    • Or incorporated within the existing boiler panel


To discuss your requirements, contact Valveforce on 0121 711 1908 or email

Applications/Case Study (Examples of Product Usage)

Whether done manually or via an automated control system, blowing down a steam boiler to maintain acceptable TDS levels helps to ensure the steam delivered to a process is both clean and dry. Permissible TDS levels vary depending on the type of boiler in operation. For example, high-pressure shell boilers have a maximum permissible TDS level of 1,000 parts per million (ppm). For horizontal fire tube boilers, this can be as much as 10,000 ppm.

To calculate the blowdown rate for a steam boiler, you will need to know the TDS (ppm) levels of the required boiler water and feed water. These values can usually be obtained from water treatment records or conductivity of samples obtained from the boiler (via a sample cooler) and the feed water line (not the make-up water).

The blowdown rate can be established using the following equation:

Blowdown Rate = FS / B-F


F = Feed Water TDS (ppm), S = Steam Generation (kg/hr), B = Required Boiler Water TDS (ppm).

Case Study - Boiler Upgrade at Milliken Industrial for Blowdown TDS and Level Control Docs

Milliken, a floor tiling manufacturer, recently needed a solution to their boiler level controls and bottom blowdown system that was out of date.

The issue with having out of date controls is that getting replacement spares can no longer be done, leading to serious issues when parts malfunction.

The company also wanted to update the boiler house to unmanned status by adding a PM5 system, which means a specially trained boiler supervisor does not need to be onsite every 24 hours in the scheme they have.

With our expertise, Valveforce advised on the best options and equipment to use to achieve these upgrades, including new TDS controls.

The turnkey project included the design of a new control panel for the whole boiler, new pipework on the TDS and a completely new TDS system.

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Valveforce Ltd specifically work alongside BSi for all aspect of our company activities by installing a UKAS accredited quality system in accordance with the guidelines laid down in ISO 9001:2015.