Pre-design drainage issues with Commercial rainwater harvesting systems

Often pre-design or design errors make RWH difficult

In our technical department, they often complain that the drainage doesn't work when it comes to the rainwater harvesting system.  They bemoan the fact that a fall or any additional access chambers haven't been drawn on the drawings.  The also complain that the rainwater harvesting system has been ordered too late and much of the drainage has been already installed, making the rainwater harvesting very difficult to function.

An order arrives

As soon as Freerain Ltd accepts an order for a commercial rainwater harvesting system, we request a copy of the latest drainage drawings to check for the following:

• Water is running downhill (we've seen many drawings showing it going up!)
• A pre-tank filter has been drawn with appropriate falls
• The storage tank location has been marked
• Only traditional roof areas are being drainage and not open gullies, drains etc

Below is a generic drawing for what a typical underground rainwater harvesting system may look like on a drainage drawing. In this case no invert level has been specified and you can see the inlet invert is 0.  Of course on site that this is anywhere from 500 to 3,000mm down.

Problems

As mentioned above there can be a number of issues and problems with getting a rainwater harvesting system to work within a commercial application.

• Drainage built with a fall for the rainwater harvesting system
• Fall in the pipework not accounted for
• Not all the intended roof is sent to the tank
• Open gullies and non-roof areas are drained into the tank

 Much of the above is really because of two reasons.  Firstly, the rainwater harvesting system is ordered/considered too late and secondly, the consultant for the drainage hasn't appreciated the requirements of the rainwater harvesting system.

Summary

Rainwater harvesting for commercial buildings and projects should be relatively easy to install, but all too often not all parties in the planning stages come together.  Therefore, on many occasions the late consideration or the lack of planning leads to costly work-arounds on site and on a few occasions this has led to already built drainage being ripped up and re-laid as required to incorporate the rainwater harvesting system.

Hose pipe bans and British made underground tanks

So after two dry Winters, the UK is facing water restrictions, affecting areas from the South coast right up to parts of Yorkshire. The last similar ban was back in Summer of 2007, when the Southern water companies issues hose pipe bans.

Some fact!
Water companies in England and Wales leaked more than 3.3bn litres a day in 2010/11, according to the regulator Ofwat.
Demand for water stands at around 17bn litres a day, according to industry body Water UK.

It would seem that the UK climate has changed over the last 20 or 30 years, with more extreme weather, since 2007, there has been a number of high profile flooding events and the focus on the management of water had shifted from water supply to the control of surface water run-off. In reality both of these issues are never going away and should be tackled together. Short terms views on either will never solve the overall problem of water management in the UK. When the hose pipe bans were announced during early March, much of the media started talking about the need to create some sort of "national water grid" in other words move water from areas where it is plentiful to essentially the South and South East. This would potentially mean an awful lot of civil engineering, at quite an environmental (and carbon) cost. There doesn't seem to be a proper debate that includes rainwater harvesting.

Taking a more local approach would seem a better option, providing there is enough water available. Rainwater harvesting as many of you know has emerged during the last 12-15 years in the UK, brought over largely from Germany. Importing storage tanks from Germany has always been one of the main criticisms aimed at rainwater harvesting.

Freerain's parent The Gusto Group has tackled this very issue by investing in a rotational moulding factory and purpose rainwater harvesting designed tank moulds. The range of underground tanks include the following features:

1) 1800 litres up to 10,000 litres
2) Single piece, no need for messy on site assembly
3) Made from virgin high strength polyethylene.
4) Installed without the need for concrete back fill or bases
5) Supplied with telescopic access shaft and pedestrian cover.

www.gustotanks.co.uk

Freerain is obviously a customer of the Gusto Group storage tanks and have a number of different control systems built around them available. Garden rainwater harvesting systems are proving very popular at the moment, as customers look to store significant quantities of water for garden use and "beat the hose pipe ban" Find the garden rainwater harvesting systems here.
Garden rainwater harvesting can be a very good way to get involved with collecting rainwater, as trying to re-plumb a house to serve toilets and washing machines to an existing can prove difficult.

Remember you can use a rainwater harvesting system in the garden with a hose pipe, providing the water company imposing the restrictions haven't supplied the water.