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Heatwave? Bring on the rain!

Who on earth was thinking about rain in the middle of a heatwave?

Well, us actually.

Somebody had to. Because, whilst the media was focused on ‘can we beat the long hot summer of 1976?’ and generally welcoming the recent heatwave – perhaps a positive distraction from so much negative news recently – we were considering its longer term impacts.

And, with an almost certain lack of political focus on the environment over the course of this parliament, it seems unlikely that there will be any top-down drive to create a leading green economy here in the UK. Progress on this agenda will need to be driven by water users themselves and by independent advisors like us.

So we’re keeping a firm eye on the weather. 

Although famed throughout the World for rain, it’s quite staggering to see just how dry the UK actually is. The Met Office’s annual average rainfall map demonstrates this, with huge swathes of our landmass receiving less than a metre of rainfall each year.

The UK Rainwater Management Association too has unwelcome news: its Sustainable Water Supplies Briefing Guide quotes a government study suggesting that we have a ‘continually deteriorating position caused by the twin pressures of climate change and population growth’ and that, ‘if unaddressed, this will result in nearly all land in England becoming unable to sustain agriculture.’

Like it or not, we need rain and we need to conserve it more effectively than ever before. That’s why we’ve been working hard to overcome obstacles in the way of the widespread implementation of water recycling measures, bringing to market next generation technologies which maximise return on investment and minimise risk.

We understand that for a commercial organisation to invest in new technologies, there has to be a clear business case with demonstrable results. Water recycling, including rainwater harvesting, can contribute significantly to many organisations’ sustainability efforts and to their bottom-line savings – but not all. A comprehensive advisory-led package is a critical success factor: this should include feasibility studies, a bespoke modular system designed for its specific location, expert installation and effective ongoing maintenance for benefits to be fully realised.

Some examples of key considerations at each stage include:

  • Site Survey – Filtering: system filters have to be suitable for the intended application and be able to cope with the flowrate according to roof size and the type of debris (such as leaves) likely in each individual location. With both passive and active self-cleaning filters through to those requiring regular user interventions, ongoing filter maintenance must be carefully considered during system design and managed effectively after implementation.
  • Design – Tank Capacity: it is imperative to ensure that the tank volume has been assessed in line with BS8515 or other approved methodology. This ensures tank capacity maximises capture, whilst ensuring sufficient water turnover to avoid stagnancy and water quality issues.
  • Design – Component Compatibility: every element of the system needs to be sized correctly to work with all the other parts and to be able to communicate properly with all the other components to ensure optimum performance and reliability over the long term.
  • Design – Header Tanks: historically it may have been preferable to utilise the main rainwater storage tank to hold mains water in the event of insufficient rainwater. This should be carefully considered as you may be filling your storage tank with mains water and excluding rainfall just around the corner. Small header or break tank based systems are usually much more suitable for integrating mains water supply backups to a rainwater system, ensuring maximum efficiency through minimum mains water usage.
  • Installation – Mains Water Back-up: although harvested rainwater is very clean, all mains water supplies in the UK are governed by the water supply regulations, this includes very specific instructions on the integration of an alternate water supply such as rainwater with the mains water system. In these cases, there must be no possibility of back-contamination of the mains water supply from your rainwater system and thus normal practice dictates the use of an air gap in compliance with EN1717 when connecting mains water to your rainwater system. Expert oversight and clear understanding is essential in this area.
  • Installation – Commissioning: this is a crucial stage and should only be completed by experts in the field. In most cases this will be the supplier or manufacturer of the system, ensuring both comprehensive commissioning, but also ongoing warranty. It should be demonstrated to the relevant facilities manager and on-site manager/owner to ensure their complete understanding of the system and that it is used most efficiently. We have been engaged to repair many systems where a thorough commissioning and client handover at the time of installation would have avoided future problems.
  • Maintenance: it is important that systems are maintained and that filters are checked regularly. An alarm system, linked to the building management system or remote monitoring system, should be installed to send early warning of any system abnormalities, so that they can be corrected immediately.

The good news is that using a professional provider who understands not only good system design, but also each project’s specific needs, can avoid all the above pitfalls and ensure systems are efficient and trouble free.

Although the benefits far outweigh the pitfalls, rainwater harvesting is not a one-size-fits-all solution. Where rainwater harvesting isn’t suitable for your needs, perhaps consider an alternative approach such as greywater or process water recycling. But don’t be put off considering water re-use in any capacity: whatever your organisation can do to conserve water is an extremely important step in setting the UK’s sustainability agenda.