Mechanical Blending Valve for Industrial Water Softeners (DN25, DN32 & DN50)

The Mechanical Blending Valve is a fully automatic mixing valve designed for use with commercial and industrial water softeners to produce a controlled level of partially softened water. Suitable for DN25 (1"), DN32 (1¼") and DN50 (2") pipework, the valve maintains a consistent residual hardness across a wide range of flow rates without the need for electrical power or continual adjustment.

Specifically developed for large-scale water softening installations, the valve automatically blends a controlled proportion of untreated raw water with softened water leaving the softener. Once the desired residual hardness has been set during commissioning, the valve continuously compensates for changing flow rates and pressure variations, ensuring a stable blended water quality under varying demand conditions.

Unlike simple manual bypass arrangements, the Mechanical Blending Valve incorporates both a main blending valve and an independent bypass valve. During periods of low demand, the bypass valve meters a precise quantity of raw water into the softened water stream. As water consumption increases and differential pressure develops across the softener, the main valve progressively opens to maintain the required blending ratio automatically. This hydraulic balancing principle provides accurate residual hardness control throughout the operating range.

The valve is installed within the bypass line of the water softener, with water flowing in the indicated direction. For installations requiring both blended water and fully softened (0 °dH) water, a dedicated shut-off valve with sampling point should be installed to allow accurate hardness testing during commissioning and maintenance.

Manufactured for industrial applications, the valve is suitable for domestic, commercial and industrial water treatment systems, operating at pressures up to PN10 and temperatures up to 90°C. Its purely mechanical operation eliminates the need for electrical controls, making it a reliable solution for maintaining consistent water hardness in demanding installations.

Technical Specification

Available Sizes

• DN25 – 1" Female BSP

• DN32 – 1¼" Female BSP

• DN50 – 2" Female BSP

Operating Conditions

• Maximum working pressure: PN10 (10 bar)

• Maximum operating temperature: 90°C

• Fully automatic hydraulic operation

• No electrical power required

• Suitable for household, commercial and industrial applications

Function

• Automatically blends softened water with untreated raw water

• Maintains constant residual hardness

• Automatically compensates for:

  • Variable flow rates

  • Pressure fluctuations

  • Changing water demand

• Single commissioning adjustment

• Installation orientation independent

Operating Principle

The blending valve continuously regulates the quantity of untreated water entering the softened water stream.

At low water demand, blending is achieved via the bypass valve alone.

As flow increases, pressure loss across the water softener creates a differential pressure that progressively opens the main valve, allowing additional raw water to enter the mixed water stream. This automatic modulation maintains a stable residual hardness regardless of fluctuations in system demand.

Installation

• Installed in the water softener bypass line

• Observe flow direction arrow during installation

• Suitable for any installation orientation

• Recommended to install a sampling valve where accurate hardness testing is required

• Residual hardness should be verified using a water hardness test kit during commissioning

If incoming raw water hardness changes significantly, the blending valve should be re-adjusted to maintain the desired outlet hardness.

Key Features

• Automatic residual hardness control

• Hydraulic operation with no electrical components

• Designed for commercial and industrial softeners

• Maintains consistent blended water quality

• Automatically compensates for pressure and flow changes

• Suitable for high-temperature applications up to 90°C

• Maximum operating pressure PN10

• Available in DN25, DN32 and DN50 sizes

• Robust brass construction

• Simple commissioning with one-time adjustment

• Minimal maintenance requirements

Typical Applications

Ideal for systems where complete softening is not desirable, including:

• Commercial water softeners

• Industrial water treatment systems

• Boiler feed water conditioning

• Heating systems

• Process water

• Manufacturing plants

• Hotels

• Hospitals

• Food processing

• Commercial laundries

• Breweries

• Large residential developments

Why Choose a Mechanical Blending Valve?

Many commercial installations require a controlled level of residual hardness rather than completely softened water. This Mechanical Blending Valve provides a reliable hydraulic solution that automatically maintains the selected hardness without electronic controls or frequent adjustment. By responding directly to system flow and pressure conditions, it delivers consistent blended water quality across varying operating conditions while simplifying commissioning and long-term maintenance.