Rainwater Harvesting Systems

Direct or indirect systems?

Direct rainwater systems are the simplest as they take the filtered water directly from the tank. For toilet flushing, for instance, this would be pumped direct to the toilet cistern. It is limited in application as it is not so easy to add multiple outlets to a direct system.

However, direct systems are ideal for garden irrigation, as they will supply water directly into the irrigation pipework.

Indirect systems use the pump to transfer the filtered rainwater to a second, header tank which is usually situated in the roof space, so that it uses gravity to supply the toilets and/or washing machine. This would reduce the pump time as it is only used when the header tank reaches a certain point. It is also easier to supply multiple outlets from a header tank, due to the gravity feed which draws off just when needed.


LDivertron Mooking at the DAB range of pumps that Tanks-UK supply. As previously described in last week’s blog, the DAB E-SYBOX system is ideal for rainwater harvest systems and is very adaptable. It is a complete electronic control panel system, not just a pump.

Another alternative is a submersible pump within the rainwater harvest tank, as these are designed to work underwater and are extremely durable. The Divertron X (illustrated) is one of the best for rainwater harvest systems.


Filtration is critical to a rainwater harvesting system. The initial filtration is fitted between the guttering and the tank and the pumps are fitted with their own filters.  Other filtration may be needed depending on the use to which the rainwater is put.

The rainwater diverter filter acts on the water as it comes through the downpipe and filters out the larger particles such as moss, leaves and algae which are discharged out of the side, whilst the cleaned rainwater flows through to the tank.

Tanks-UK supply rainwater filters from Enduramaxx, Nikeson and other manufacturers.

UV Treatment systems

UV (ultra-violet) sterilisation could be an essential part of a rainwater harvesting system, if you are going to use it for anything such as washing.

UV sterilisation could be an essential part of a rainwater harvesting system, if you are going to use it for anything such as washing. Normally rainwater is not considered potable water in the UK, but under certain circumstances where mains water is not available, it can be if it is UV treated. UV sterilisation does not filter particles from the water but simply kills bacteria and removes microbiological contaminants such as fungi, protozoans, viruses, and cysts. UV rainwater sterilisation is a safe and effective method to disinfect water.

What is a Calmed Inlet?

The idea of a calmed inlet is that, instead of water pouring into the top of the tank and stirring up any sediment, it flows through a specially created u-bend lower down the tank. This means that the water flow is upward into the tank itself, reducing turbulence and keeping the water cleaner.


Rainwater harvesting is actively encouraged in the UK and it may be possible to part-fund systems by way of a grant. It is of benefit to the wider environment in reducing flooding, pollution and use of mains water supplies, therefore these would often come under environmental improvement schemes.

If you are in the Agricultural sector, there are a variety of Government Grants available under the Countryside Stewardship scheme. Check out RP19 which covers the rainwater diverters and filters, and RP18 which relates to above ground tanks.

It is also worth checking with local authorities and regional water authorities as to what grant schemes are running – these do vary from year to year.


Just give us a call on 01953 665940 or email info@tanks-uk.com with your requirements and we’ll send you a quote.