Don’t just take our word for it

  • Thank you for your household HS38 product. I received it and i found it improved the quality of the water in our house.

  • My HS38, installed in October 2017, is doing a great job. I live in a hard water area, so the results are easy to observe.

  • I'm so glad my friend recommended the HydroFLOW hs38. Works great. Set it up in less than 20 mins.

  • I can't stop talking about it! I got rid of my salt system headache, and de'crusted' all my fixtures and appliances. It works, It's brilliant, and eco friendly - I could go on and on...

  • I purchased the HydroFLOW hs38 about 6 months ago. I found it easy to install, with a little D.I.Y. knowledge and subsequently found my boiler to run quieter as time moves on. I'm very grateful of the technology used for a quieter life.


Chemical-free technology

With its innovative patented design and unique, electronic signal, the hs38 is a cost effective and green solution for conditioning water.


Protects your appliances

Designed to protect your appliances such as boilers, dishwashers and washing machines, and to make limescale-stained taps, sinks and bathtubs easier to clean.


Saves you money

The HydroFLOW hs38 is designed to reduce limescale in your home, allowing you to be more energy efficient, saving money on bills.

Sold in over 40 countries worldwide

HydroFLOW hs38

Limescale can be a major problem in hard water areas, causing blockages, requiring replacement of equipment, and decreasing heating efficiency and thereby increasing costs. Just 0.8mm of limescale can decrease heating efficiency by as much as 10%*. Observations have shown that the use of a hs38 may over time, lead to a reduction in the existing and problematic hard encrusted limescale from heating surfaces. Less limescale means greater efficiency.

The HydroFLOW hs38, first developed in the UK in 1992, represents the pinnacle of domestic limescale protection.

With its innovative patented design and unique, electronic signal, the hs38 is suitable for installation in houses of up to four bedrooms, and can protect combination boilers as well as vented and unvented cylinders.

The hs38 is designed to protect against hard limescale deposits in domestic pipelines and on heating elements and surfaces, to protect appliances such as dishwashers and washing machines, and to make limescale-stained taps, sinks and bathtubs easier to clean.

How does the HydroFLOW hs38 work?

Protecting the heart of your home

Two cylinders were removed from neighbouring houses in the hard water area of Farringdon, South Oxfordshire. The plumber noticed one was much heavier than the other and opened them up to see why.

The heavier cylinder (left) contained lots of hard scale which would have reduced efficiency and loss of hot water volume.

The lighter cylinder (right) had been protected by a HydroFLOW hs38, and the cylinder and coil remained clear of limescale, keeping them operating at maximum efficiency.

Without <em>Hydro</em>FLOW

With <em>Hydro</em>FLOW

About <em>Hydro</em>FLOW

There is no need to cut pipes, or drain down your system. The unit simply clips to the pipe, and is plugged in or wired into the electric supply and switched on. Installation is very straightforward.

A custom made strap is provided which fits up to 28mm outside diameter. However if required the unit can fit a pipe size of up to 38mm outside diameter (without the use of the strap).

Due to the unique way that HydroFLOW transmits the signal up and down the whole water system, we recommend that the unit be installed on the cold feed to the heat exchanger. In the case of a traditional gravity-fed system, this would be the down pipe between the cold water storage tank and the hot water cylinder. With a mains pressure system, the unit should be fitted on the cold feed, just before it enters the heat exchanger.

Yes, in the UK there are two versions of power supply. The HydroFLOW hs38 “A” version is one that requires an electrician or qualified person to wire it into a fused spur. The HydroFLOW hs38 “B” version has a 13amp plug with an in-built transformer that can be plugged into a suitable socket.

PLEASE NOTE that this HydroFLOW hs38 is a 240V 50Hz model designed for the UK market, and will not operate outside the UK.

The HydroFLOW hs38 does not change the chemical composition of the water in any way. It works purely on a physical basis, leaving the water completely drinkable. Essential minerals are retained in the water. Unlike water softeners, it is not necessary to provide a separate untreated drinking supply.

Yes, although it may be a gradual process over a period of months. The way in which HydroFLOW prevents limescale from forming on pipework also increases the solvicity of water – meaning that any limescale which had already formed will gradually dissolve. However, not all scale is limescale. Some scale cannot be dissolved and can only be removed by acid cleaning. Once a system is cleaned it is less likely to scale up again.

Yes, HydroFLOW hs38 is not dependent on water flow, like other devices. The water does NOT have to flow past the unit to be treated. Rather than taking the water to the treatment, we are taking the treatment to the water. Our patented signal transmits along conductive materials, e.g. water or metal, and therefore throughout the whole system (primary and secondary), protecting it 24 hours a day

The HydroFLOW hs38 only uses a maximum power of 1.2 watts when connected via it 12v AC transformer. This is approximately just over £2 a year in the UK. This price, however, depends on the current electricity prices.

The bright red light on the unit is powered by the signal itself, and can be relied upon to indicate that the system is being protected.

About Limescale

Limescale largely consists of calcium carbonate deposit. It is a mineral residue which often adheres to heating surfaces inside of pipework, in a hard plaque or tartar-like layer.

In the home, limescale is often most noticeable on taps, in sinks and bathtubs, on showerheads and on the inside of domestic appliances such as kettles and dishwashers.

Water which is pumped to houses contains minerals. The level of these minerals will vary, depending on the geological make-up of the surrounding area, the way in which the water has been sourced (it may be ground water or surface water) and how it has been filtered for human consumption. In areas with ‘hard water’ (see map and explanation below), the water generally contains a relatively high amount of minerals when it reaches the home.

When water is rapidly heated, such as in a domestic heating system, this causes the minerals contained within the water to no longer be dissolved in the water and to stick to nearby surfaces (such as to the inside of a pipe, or to the plates of a heat exchanger element). Over time, layers of these mineral deposits build up and cause scaling or ‘furring’ in the plumbing system.

When heating surfaces are covered with scale, their ability to transfer heat into the water is reduced. As a consequence, the efficiency of the system is affected. This has a knock-on effect on your domestic energy bills in your home.

Additionally, the presence of limescale on taps, in sinks, in bathtubs and inside kitchen appliances can necessitate intensive cleaning on a regular basis. This regular removal of hard scale deposits by cleaning can be time-consuming and may also involve the use of hazardous or unpleasant chemicals.

See our below map for an at-a-glance guide to hard water areas in the UK and Ireland.

Hard water is characterised by leaving residual scum marks on the inside of cups, bathtubs and sinks, and by taking longer to create suds when soap is added to it. It is also often said to leave a chalky aftertaste in the mouth. Limescale is a very common occurrence in homes situated in hard water areas.

However, pockets of hard water can still occur in areas which are deemed to have soft water, depending on the source of the water supply (which can sometimes be unexpectedly changed by your supplier, for example during shortages) and on the specific geological conditions of an area.

You may therefore still see limescale occurring in your home even if you live in an area which generally has soft water.

The HydroFLOW hs38 is a patented electronic water conditioner. It is a piece of equipment which fits around pipework and transmits an electronic signal into the water contained within. The signal propagates around the entire pipe system and causes the limescale present in the water to form into loose clusters. When the water is heated these clusters form crystals in suspension in the water which normally wash away with the flow, so that they no longer adhere to the inside of the pipework or to any other surfaces. Over time (depending on flow rate, water parameters, amount of heating etc), existing limescale which has already been formed in the system will begin to erode, again washing away with the flow of the water.

The HydroFLOW hs38 is environmentally friendly and easy to install – it involves no use of chemicals and requires no cutting or rearrangement of pipework. The HydroFLOW hs38 unit runs off a standard power supply – all units are supplied with a standard plug and 3 metre-long power cable.

Unlike water softeners, the HydroFLOW hs38 does not chemically alter the water. This means that the minerals are all still present. When the water is heated the minerals will form as powder. In most cases, this is washed away with the flow of water.

However, if the flow rate is low, then a small amount of this powder can build up over time, for instance in the bottom of a hot water cylinder, with the amount depending on the flow rate, hardness of the water and system configuration. If desired, this powdery residue can be dealt with by an occasional drain down or cleaning of the system.

You may require the installation of a slightly more powerful unit.

Please contact the UK office or your local dealer if you are not based in the UK.

If you need assistance with preventing limescale or biofouling, or if you wish to improve filtration in a commercial or industrial application (such as in a cooling tower, swimming pool, water treatment plant or other setting), please take a look at the rest of our product range and contact the UK office or your local dealer if you are not based in the UK.


1. Ministry of Health, Water Softening, Report of the Sub-committee of the Central Advisory Water Committee, 1949

2. UKWTA Study by Advantica 2005

3. Heat Transfer Implications of Scaling and Fouling in Cooling Water Systems – RK Deshpande & DJ Banerjee of Aquapharm Chemical Co. Pvt. Ltd. Pune-411.026 published in Corrosion and Maintenance Journal July-Sept. 1984

4. Federal Technology Alert – Non-Chemical Technologies for Scale & Hardness Control published by US Department of Energy Jan 1998

5. Effect of Scale Deposits in Boilers – Results of studies made by the University of Illinois and the US Bureau of Standards published in National Institute of Standards and Technology, Handbook 115, Supplement 1 Carbon Trust Technology Overview CTV008