Rain water harvesting system building regulations

There are no regulations that govern rainwater harvesting. But, Building Regs do affect positioning of tank and the internal plumbing of the storage tank.

rain water harvesting system

There are currently no regulations that govern rain water harvesting systems. However, there are Building Regulations that do affect the positioning of the tank and also the internal plumbing of the storage tank. This will provide you with a guide to better understanding the Building Regulations that a good installer should already be aware of.

Rain water harvesting system regulations:

Building Regulation Part H:

This section of Building Regulations refers to Drainage and Waste Disposal and would be applicable when installing a rainwater harvesting system.


H1 Foul Water Drainage:

Low Flush WC’s - In the case of low flush WC’s guidance is now being provided in order for the design pipework of such systems to be efficient and sanitary.

Drain Pipe Size - If drains or sewers are providing for more than 10 dwellings they must be a minimum of diameter of 150mm.


H2 Waste Water Treatment Systems and Cesspools:

Maintenance Information - This requires that a notice should be visible in an appropriate place which should set out the maintenance procedures in order to inform both consumer and installer.


H3 Rainwater Drainage:

Sustainable Rainwater Drainage - Guidance is now provided on the use of infiltration drainage systems.

Rainfall Intensity - Additional guidance is now provided detailing information on the intensity of the rainfall and how it would affect rain water harvesting systems.


H5 Separate Systems of Drainage:

This is a new guideline that lays out the circumstances where there may be a requirement for separate systems of drainage.

It is essential that these Building Regulations be adhered to when installing rain water harvesting systems.


Building Regulations Part G:

This section covers the requirements for Sanitation, Hot Water Safety and Water Efficiency.

G1 – There is now a requirement for wholesome clean drinking water. This is of course why it is not advised to use the rainwater that is collected from your roof as drinking water.

G1 also requires that an amount of water that is of a suitable quality and sanitary be fitted with a flushing device.


Image Sourced: Chiot’s Run

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