Information on Commercial Rainwater Harvesting
Types of Systems
Commercial rainwater harvesting can be achieved through different types of systems depending on the size, location, and intended use of the development. Our estimating team are on hand to offer you the best solution to maximise water savings; as a guide, here are the different types of commercial rainwater harvesting systems available on the market.
Non-Pressurised
A non-pressurised or gravity-fed rainwater harvesting system is made up of a double storage tank arrangement. The first tank is the main storage tank for harvested rainwater. A secondary, smaller break tank is internally located within the building to provide a sufficient supply of rainwater to cover the demand from outlets and houses the automatic mains water top up.
Non-pressurised rainwater harvesting systems can provide the largest volumes of reclaimed rainwater making the system type ideal for large commercial developments. Sports stadia, leisure venues, hospitals, and manufacturing facilities are all ideal building types for non-pressurised rainwater harvesting.
The secondary break is usually located at low level within a plant room to mitigate the risk of legionella developing within the tank.
Combi
Combi Rainwater Harvesting is simply the combination of pressurised and non-pressurised technologies. A single control panel houses electrical controls, an internal break tank, and a twin booster set. Combi Rainwater Harvesting is ideal for where above ground space is limited as all components are housed in one, compact unit rather than a large plant area being required for a secondary break tank.
Combi Rainwater Harvesting is ideal for most types of commercial buildings, including schools, distribution centres, public buildings, and transportation depots.
This type of system is the most common type of installation in the UK due to the ease of installation offered by a single mechanical and electrical control panel.
Pressurised
Pressurised or boosted rainwater harvesting systems are only made up of a single main storage tank for all reclaimed rainwater. A sufficient supply of rainwater for points of use is achieved through a pressure vessel located internally within the building. The pressure vessel will be sized based on usage requirements to ensure there is always enough water to cover demand. Rainwater is then boosted to points of use via a booster set.
Failsafe implications should be considered for pressurised rainwater harvesting. The system is reliant on the continuous operation of the pressure vessel; therefore, planned preventative maintenance is especially important for these types of systems. Should the pressure vessel experience a failure, there will be a lack of supply to usage points.
Pressurised or boosted systems should only be utilised where there is no above ground plant space available.
StormStation
StormStation is an all-in-one system which houses storage tank, filters, controls and a booster set. StormStation Rainwater Harvesting offers the simplest installation available on the market due to having a plug and play operation.
StormStation Rainwater Harvesting is suited to retrofitting to an existing building, installation on newly constructed developments, and as a temporary solution during the construction phase for site welfare cabins.
Considerations for Commercial Rainwater Harvesting
System sizing – commercial rainwater harvesting systems are sized using local rainfall data, collecting roof area, and total demand from outlets served by the system. The main storage tank of a commercial rainwater harvesting system is sized based on 18 days’ worth of storage capacity to ensure the rainwater is not held for extended periods of time. This is in accordance with BS 16941:2018 of the British Standard building regulations.
Maintenance requirements – commercial rainwater harvesting systems require bi-annual servicing and a full tank clean every 2-3 years as part of planned preventative maintenance by the end user. Systems located in areas of intensive avion activity may require more frequent tank cleans to remove contaminants; however, this should be assessed on a site-by-site basis.
Automatic backwash filters are a method of reducing maintenance requirements for the end user. Automatic backwashing does not require physical replacement of a filter to be carried out.
Rainwater Harvesting Systems should not be bypassed under any circumstances and a physical air gap between the rainwater and mains water pipework must be maintained at all times. This is in accordance with WRAS cross-contamination regulations.
Main storage tanks – commercial rainwater harvesting can work with above or below ground storage tanks. These can be single piece GRP (glass reinforced plastic) tanks or sectional tanks which can be constructed where site access is limited. Above ground tanks require a flat concrete base to prevent the tank from cracking.
Where the site has a high water level, an above ground tank maybe required or specialist reinforced concrete will be needed to secure the underground tank. Our team will be on hand to advise further.
Installation – installation of commercial rainwater harvesting systems should only be carried out by trained specialists. First, civils contractors or the main contractor will need to install the underground tank early on in the construction phase. Next, the mechanical contractor should run pipework and electrical connections from the pipework from the storage tank to the plant room. Stormsaver can then make the connections within 5m in the plant room and get the system up and running for an additional cost.
Things to watch out for…
- Pipework connecting the submersible pumps in the main storage tank should be installed with straight lengths of MDPE pipework rather than coiled. This will prevent the submersible pump from falling over.
- Always use black and green MDPE identification pipework to notify any future contractors that the water within the pipework is not for potable consumption.
For retrofit projects, Stormsaver can offer complete installation solutions. Just speak to our team about your proposal
