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Horne In-Line Thermal Disinfection Unit


For routine thermal disinfection of showers, taps, TMVs, their associated pipe-work feeds, ancillary fittings, mixed water deadleg and terminal outlet fitting using the readily available system temperature hot water supply. Fits to hot and cold supply pipework drops and includes 2 No. 3-way ball valves, connected by four way link mechanism for switch between passive and disinfecting mode. Connections by compression fitting for 15mm copper pipe. Manual operation using bespoke key with safety warning (supplied separately).  

Part Number: ILTDU

Designed and manufactured by Horne Engineering Ltd.

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How it works

The HORNE ILTDU passes hot water from the Domestic Hot Water System through the downstream pipework. It diverts hot water to both the hot inlet and the cold inlet of a downstream mixing device. This overrides the so-called “fail-safe” characteristic of the mixing device and thus raises the whole mixing device to system hot water temperature. This effects disinfection of the mixing device and its associated components, local pipework as well as the terminal outlet fitting.

The HORNE ILTDU has two operating modes – PASSIVE and DISINFECTING. In PASSIVE mode, the ILTDU passes the hot and cold water supplies straight through to the mixing device, which operates as normal.

An OPERATING KEY is used to switch between PASSIVE and DISINFECTING modes. A single clockwise half turn of the OPERATING KEY activates DISINFECTING mode. 

How it works Schematic for Horne In-line Thermal Disinfection Unit (ILTDU)

Why use the ILTDU?

Disinfection: the reduction of the number of pathogenic micro-organisms to safe levels.

Via the incoming water supply and by retrograde contamination, Psuedomonas, Legionellae and other pathogens can colonise the last two metres of domestic water supply (DWS) pipework, including the outlet fitting (any TMV, tap or shower). This problem is specifically described in Health Technical Memorandum (HTM) 04-01, Part C.

Our In-Line Thermal Disinfection Unit (ILTDU) facilitates periodic high temperature thermal disinfection using the readily available hot water supply. Now the thermal regime can be extended to the point of water discharge: therefore, the wetted surfaces of all downstream components, including the mixing valve and the outlet fitting, can be raised to system temperature.

The narrated animation above provides further information about the ILDTU: explaining how it works, outlines safety considerations and also includes thermal imaging camera footage of the Optitherm tap fed via an ILTDU in disinfection mode.

Combine the disinfection process with pipework flushing at an elevated velocity using a Flushing Kit.  This serves to shear excess biofilm from the internal pipe surfaces and remove it to drain, thus improving water quality and reducing the contamination risk.

Hospital Trials
Results of initial hospital trials have proven the ILTDU to be highly effective in reducing Pseudomonas cfu counts to zero following a single treatment and replacing the need for POU filters. Read our case study from St Richard's Hospital in Chichester here.

Shower Panel Integration
Horne TSV1 shower panels are now available with the ILTDU built-in and are supplied with an adapted Pipe Cover (with access slot for key operation) available in 465mm (T4 variant) or 940mm lengths (T9 variant). 


The In-Line Thermal Disinfection Unit is a patented Horne design


  • WRAS approval number 1511330 (external link)
  • All HORNE products are manufactured under our Quality Management System to BS EN ISO 9001:2015. Certificate No. FM 01224

Useful Documents

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