Why The Water Industry Act 1991 is impacting use of communal rainwater harvesting systems
08/04/2025
Introduction
The Water Industry Act 1991 was put in place to consolidate existing water supply and sewage service laws and laid the groundworks for the water industry we know today. However, in order to combat the numerous water scarcity issues the country is facing in its present day the act will require updating to make it fit for the growing technology of rainwater harvesting and greywater recycling.
This week, our blog will take a look at the act in relation to dual pipe water reuse systems. We’ll be taking a deep dive into the following areas…
- Current limitations with the act.
- Current water scarcity issues facing the UK.
- Our solution to improve water efficiency in new homes.
- The steps we will need to take for this to be successful.
The problem – limitations with the current act
The current version of the act is limiting our ability to reduce the water scarcity issue through reuse technologies.
Currently, the legislation prevents water companies from providing a dual water supply to our buildings, meaning that reclaimed water such as rainwater and greywater is not legally allowed to be supplied by water supply companies for non-potable uses. This is evidenced in section 68 of the act, “Water Supplied by water companies should be wholesome at time of supply”.
Let’s break this down. The term “wholesome water” refers to water of drinking quality only. Additionally, domestic use is defined in section 218 of the act as “drinking, washing, cooking, central heating and sanitary purposes”
This ultimately means that water companies cannot supply rainwater and greywater for non-potable uses. This matters for domestic water reuse. Without changes, this legislation makes it difficult to install communal-scale water reuse systems across new housing developments in the UK. Allowing a communal dual supply system would take pressure off mains water supplies, reduce surface water runoff, and help during build resilience to droughts.
The problem – water scarcity in the UK
Why is water scarcity such a big problem?
Demand for potable water is rising at an alarming rate and water companies simply cannot sustain these growth rates.
The Environment Agency has predicted a 5 billion water deficit by 2050 based on forecasted usage growth and supply. Much of England has already been classified as seriously water stressed meaning that demand in those regions is dangerously close to exceeding supply. As well as this, water neutrality has already been put in place in West Sussex, meaning that new developments cannot use any more water than the land did previously.
Water efficiency in new homes
With all these water scarcity issues, the Building Regulations 2010 (specifically Part G) has been brought into place meaning that new homes must be specified to no more than 125 litres per person per day (LPPPD) and it is recommended that in water stressed areas new homes be specified to 110 LPPPD, however this lower rate is not enforced.
In spite of the enforced specification of 125 LPPPD a report by The Home Builders Federation has found that new home usage is actually reaching 150 LPPPD. Rainwater Harvesting can reduce usage in homes by 25 LPPPD meaning it can bridge the gap between the governments set 125LPPPD and actual usage of 150 LPPPD.
The solution – communal systems
We believe that the best approach to saving water on large residential developments is through Communal Rainwater Harvesting. We believe that the best organisations to own and adopt these systems are water companies, which cannot happen at the moment due to section 68 of the Water Industry Act!
Enabling Water Smart Communities “Water Reuse in New Housing” report found that the communal system approach to rainwater harvesting was up to 50% more cost effective to install than the individual plot approach.
Communal Rainwater Harvesting also provides other benefits when compared to individual plot systems including:
- Safety – By relocating the rainwater harvesting controls to external “water substations” around the development, the risk is greatly reduced. Individual plot systems use controls located within homes which can lead to homeowners tampering with systems. It’s more tamper proof!
- Lower Maintenance costs – By having one large communal system, there is a significant reduction in maintenance costs when compared to the cost of servicing systems individually per home. You also do not have to access each home with a communal system, meaning less logistics and administrative work.
- Long term savings – By having a communal system which is properly owned, you can guarantee the system is working, rather than on individual plot systems where the homeowner is responsible for the operations. Communal systems also use commercia-grade components, ensuring high levels of reliability.
Key enabling steps
We believe that every new home and non-household property in the UK should be designed with water reuse systems as standard, every property built without is a future problem for water supplies.
The Ricardo report found that retrofitting rainwater harvesting was 50% more expensive than installation at the new build stage. This is why getting these systems included at the design stage is so important in order to not only reduce costs but to make sure the development has the most efficient water reuse system possible!
In order to see this happen we will need to see changes to section 68 of the Water Industry Act 1991 to allow non-wholesome water to be supplied to homes by water companies for non-potable uses such as flushing toilets, irrigation and car washing. There are other regulations that will need changes, for example Part G of the Building Regulations but we will cover this in future blogs.
Next steps
Luckily, the new government has committed to reviewing this legislation with the aim allowing water companies to introduce dual supplies.
Therefore, we are encouraging housing developers and water companies to hold early discussions with us around how communal solutions could work for your organisation. Get in touch with us to set up a discovery call to find out more. Alternatively, have a look at our communal solution here!
