Click on the video below to see how the CleanflowCPR works

Case study

This case study is of a scheme of 130 dwellings in Hampshire. The development was constructed between 2010 and 2012.

The video below shows how badly contaminated the system was. At the time of the video the scheme was 2 years old and almost all of the 130 units were losing their heat supply on a regular basis (weekly and, in some cases, daily). Residents were constantly reporting loss of heating, despite many having their strainer cleaned the previous day. In some cases engineers were cleaning strainers, only for them to re-block within a few hours.

The hose you can see in the video was attached at one end to the strainer outlet of the HIU, and the primary flow valve was opened to flush the debris through the hose into the WC pan. A sample of debris was sent to a laboratory for analysis and was found to be made up of a combination of limescale, metallic corrosion and biological growth.

In Winter 2013, to reduce delays between report and response, the landlord employed a team of engineers on site every day, responding to callouts as they came in. However, the situation became so bad that residents publicised their frustration and the BBC featured the scheme on its Watchdog programme.

As the situation continued to get worse the landlord arranged for a high pressure manual flush to try and force the debris out of the pipes. This involved flushing the entire primary network of over 500m of underground pipes and vertical and lateral pipework across the scheme. However, as there were no bypasses on the network, all of the water in the primary network had to pass through the strainer in the HIUs, forcing the debris into the strainers and the HIU plates. The landlord then arranged access into all 130 units to flush individual HIUs. The whole flushing process cost over £60k and was very disruptive to the residents.

In addition, all 130 HIU heat exchanger plates had to be replaced as they were blocked as a result of forcing debris at high pressure through the HIU strainers into the plates.  

However, as the flushing process only removes debris that is suspended at the time of the flush, a significant amount remained in the system, hanging onto bends, areas of low flow and lining the insides of the pipework, only to fall into suspension after the flush. As a result, although the flush improved the situation, debris continued to block HIUs.


Interestingly, the addition of inhibitor and biocide after the flush only served to soften the debris that remained in the system, releasing it into suspension, with the result that the HIU strainers continued to block.

Having flushed the system without success, the landlord decided to install Cleanflow CPRs to all 130 units.

Complaints about poor/no heat supply stopped immediately.


This photo shows a typical blocked strainer BEFORE the Cleanflow CPRs were installed

The photo above shows the Cleanflow CPR installed inside the HIUs in the Hampshire scheme. 

Since they were fitted in 2015, there have been no callouts due to blocked strainers and the Cleanflow CPRs continue to clean the primary network every day, moving any debris that finds its way to the HIU back to the plant room filters and maintaining a reliable heat supply to the residents.

More importantly, because the HIU strainer is automatically flushed every day, residents enjoy a reliable heat supply and aren't aware that the system may have debris in it.

Below you can see the Cleanflow CPR assembly retrofitted into another scheme. You can see that its position redirects any debris from the primary flow into the return, bypassing the HIU and protecting the heat exchanger and other sensitive components that are easily damaged by debris, eg actuator valves. This results in maximum flow and a reliable heat supply at all times.