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  • Using temperature to detect intermittent toilet leaks

    Acoustic methods of leak detection cannot find all forms of plumbing leaks on their own. Invenio’s StopWatch technology is uniquely positioned to find all forms of plumbing losses, especially the regular interval toilet leaks highlighted by Carmen Snowdon in her LinkedIn article. Invenio have also found that plumbing losses are 3 times more likely to occur (and continue unresolved) on unmetered properties. With Stop.Watch’s non-invasive sensing technology, this enables effective leak detection on all forms of stop taps.


    In September 2020, the BBC released a news article highlighting the prevalence of ‘Leaky Loos’. The article estimated that a shocking 400 million litres of water is wasted through toilet leaks in the UK every day and assigns the blame to leak prone dual-flush toilet systems. These toilet systems are designed with a low and a high flow flush option in an effort to reduce the amount of water used. However, it appears that these systems are more prone to leakage than traditional ball valve toilets systems.

    The following day, Carmen Snowdon, Head of Commercial Services at WRc, published a response to this article, identifying a distinct pattern in high resolution flow data measured in domestic properties where the valve periodically opens and closes, releasing around 1 litre of water per event at regular intervals of a few minutes throughout the day and night: regular-interval plumbing loss events.

    Invenio Systems have used their “Stop.Watch” technology to perform leakage surveys on over 50,000 stop taps since 2015 in the UK and abroad. Invenio’s technology, based on high precision temperature measurements, which do not require a meter, is focussed on detecting customer-side leaks and plumbing losses: where traditional acoustic methods are often ineffective.

    The Stop.Watch system has identified thousands of customer side leaks. We have found that regular-interval plumbing loss events from domestic properties occur in 1.7% of properties surveyed. The frequency of these detected events can vary between 1 and 10 events per hour: giving an average flow rate around 1.75 l/hr.

    Figure 1: Data Collected by Invenio’s Stop.Watch device showing a stop tap of a property with no leak present.

    Figure 2: Stop.Watch data showing the regular flush pattern of a broken toilet cistern. The frequency of these flushes is approximately 18 minutes.


    Admittedly, this does not sound like a huge concern, after all, these leaks are tiny in comparison to the larger network side leaks, which can typically reach over 1,000 litres per hour. Traditional leakage detection methods (particularly on the customer side) rely on acoustic listening sticks and skilled engineers to identify leaks. However, due to the start/stop nature of these toilet leaks, and given that a leakage engineer is unlikely to spend 1 hour listening to each stop tap during a leakage sweep of an area means, these leaks are unlikely to be detected using traditional methods. So, it is likely that these small toilet leaks continue without the awareness of the customer or the water company.

    Stop.Watch surveys also detect, quantify, and categorise continuous flows and more irregular events where, for example regular-interval plumbing loss events occur only at night or toilet leaks start and stop over a scale of a few days.  Typically, a further 5% of properties have this type of plumbing loss at any one time.

    Figure 3: Stop.Watch data showing an intermittent flushing pattern. The frequency of these flushes increases throughout the logging period, indicating that the mechanism may fail completely soon.

    Figure 4: Stop.Watch can also find much large leaks. Data above shows the presence of a 940 l/h leak on a supply pipe.


    Taken together, the regular-interval plumbing loss events and the more significant intermittent and continuous plumbing losses make up between 1 and 2 litres per property per hour of night flow: a significant proportion of the “background”, “base”, or “minimum achieved” leakage that are a large part of reported leakage in most UK water companies.   These plumbing losses are three times more common on unmeasured properties than measured ones. However even on smart metered properties the regular-interval plumbing loss events will not be detected as plumbing losses.

    OFWAT, the UK water regulator, has tasked UK water companies with reducing leakage by 15% between 2018 and 2025, and with the ultimate aim of ‘Zero Leakage’ by 2050. To aid Water Companies with this, Invenio have worked with most of the UK’s major water companies to tackle the leakage problem, both customer side and network side.

    The first step in solving any problem is to recognise there is one. Leaky Loos are a significant problem to both the customer and the water providers. Several studies have highlighted this significant problem of Leaky Loos.  Now, WRC and Invenio have both highlighted another form of Leaky Loo, one that is unlikely to be detected using traditional leakage detection methods.

    Written by John Dolan

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Scottish Water are delighted to be working with Invenio Systems and are excited by the potential their innovative technology has to help identify and assess leakage.

Martin Walton, Scottish Water

Invenio Systems

Martin Walton, Scottish Water

Scottish Water are delighted to be working with Invenio Systems and are excited by the potential their innovative technology has to help identify and assess leakage.
Invenio Systems

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