---
title: "What is Silicates mg/L?"
description: "Silicates are naturally occurring mineral compounds that may also be present in some heating-system treatment chemicals. At appropriate levels they can contribute to corrosion protection, while unusually high or unstable levels may indicate over-treatment, contamination or a risk of deposit formation within the system."
url: https://help.fernox.app/en/articles/161-what-is-silicates-mgl
collection: "Chemical Parameters"
updated: 2026-10-02
language: en
alternates: [es, de, nl, fr, nl-be, fr-be, ro, cs, pl, sv, tr, sk]
---

# What is Silicates mg/L?

Silicates are naturally occurring mineral compounds that may also be present in some heating-system treatment chemicals. At appropriate levels they can contribute to corrosion protection, while unusually high or unstable levels may indicate over-treatment, contamination or a risk of deposit formation within the system.

### Silicates — mg/L

**Technical definition**  
Silicates are a measurement of the concentration of **dissolved silicon-containing compounds**, typically present in water as soluble silicate species, expressed in **milligrams per litre (mg/L)**.

Silicates can occur naturally in mains water as a result of contact with minerals and rocks, but they may also be introduced into a heating system through **water-treatment chemicals, corrosion inhibitors or certain cleaning products**.

Within closed heating systems, silicates can form part of some **corrosion-inhibitor formulations**, where they can help create a protective layer on metal surfaces. However, if present at excessive concentrations or under unsuitable water-chemistry conditions, silicates can also contribute to **deposits or precipitates** within the system.

**Simplified definition**  
Silicates are naturally occurring mineral compounds that may also be present in some heating-system treatment chemicals.

At the correct level they can help protect metal surfaces from corrosion, but unusually high levels can indicate over-treatment, contamination or conditions that may lead to **deposits forming inside the heating system**.

### Why are Silicates important to test?

Silicates are important because their presence can provide useful information about both the **original filling water and the chemical treatment used within the heating system**.

An abnormal or elevated Silicates result may indicate:

-   Naturally high silicate levels in the original mains or filling water.
    
-   The presence of a **silicate-containing corrosion inhibitor**.
    
-   Excessive dosing of a treatment product containing silicates.
    
-   Residual cleaning or treatment chemicals remaining within the system.
    
-   Contamination from another water or chemical source.
    
-   Changes to the system water following refilling, treatment or maintenance.
    
-   Conditions that could encourage silicate-containing deposits to form.
    

Where silicates are deliberately included in an inhibitor formulation, they may help protect metallic surfaces by contributing to the formation of a **thin protective film**, reducing direct contact between the metal and the circulating water.

However, silicate chemistry is strongly influenced by factors such as **pH, temperature, concentration and the presence of other dissolved minerals**. Under unsuitable conditions, silicates can become less soluble and form deposits.

Excessive or unstable silicate concentrations may therefore contribute to:

-   Deposits on heat-transfer surfaces.
    
-   Fouling of heat exchangers.
    
-   Restricted flow through narrow waterways.
    
-   Deposits within valves and other small components.
    
-   Reduced heat-transfer efficiency.
    
-   Unwanted interaction with other water-treatment chemicals.
    
-   Cloudiness or particulate material within the system water where precipitation occurs.
    

Silicate testing can also be diagnostically useful when the treatment history is uncertain. A significantly higher silicate concentration in the system water than in the original filling water may indicate that a **silicate-containing chemical product has been added**.

Silicates should therefore be considered alongside parameters such as **pH, Conductivity, Suspended Solids, Sodium, Molybdate and other treatment-related indicators** when evaluating the condition and treatment history of the heating system water.

### Important interpretation note

Silicates should **not normally be assessed in isolation**. Their significance depends heavily on the **source of the silicate and the treatment chemistry used within the system**.

A measurable silicate concentration is not automatically a problem. Some silicate may naturally be present in the incoming water, while certain corrosion-inhibitor products may deliberately introduce silicate as part of their protective chemistry.

Likewise, a high silicate concentration does not necessarily mean that deposits are currently forming. The likelihood of precipitation or deposition depends on several interacting factors, including **pH, temperature, overall concentration, water hardness and other treatment chemicals**.

It is therefore particularly useful to compare the system-water result against the **original filling-water silicate level, previous laboratory results and the known inhibitor or treatment product used**.