Flow rates and flush volumes: BREEAM compliant commercial washrooms

Reading time: 5 minutes

Most Architects strive to achieve an Outstanding BREEAM performance level to demonstrate the environmental impact of the construction processes, materials used, and operations in all elements of their building. On their journey to BREEAM certification, the most common question we get is, “we are looking to achieve a BREEAM Outstanding/Excellent rating, can you help me achieve the required flow rates and flush volumes?”

From design to compliance with UK water regulations, we know the intricate details in all aspects of a commercial washroom and understand the importance of supplying washroom products that align with green building rating standards.

We can guide our clients in the right direction to achieve the BREEAM rating they desire by helping them select sustainable washroom products and to understand the importance of BREEAM flow rates and flush volumes of all the water components.

In this article, we will take you through the numerous BREEAM standard flow rates and flush volumes in all the water components applicable to a commercial washroom in your new build or renovation.

What are the main BREEAM water components in a commercial washroom?

  1. Taps
  2. Toilets
  3. Urinals
  4. Showers (particularly in EoT areas)
  5. Greywater/rainwater

Let’s explore the water efficient consumption levels by each component type: 5 credits being BREEAM Outstanding performance.

BREEAM Tap flow rate

Taps that reduce flow rate include a flow restrictor either at the end of the spout or in the water feed. It regulates the water flow to a maximum flow rate and prevents water from shooting out by force. Without a flow restrictor, the pressure overflow can force the water to gush out the tap in mass quantities. This results in water wastage and energy wastage if the water is heated for handwashing.

As per the table below, BREEAM has set aside 5 credits (Outstanding rating) up to a 3 litre flow rate per minute for hand wash basin taps. Anything above 3 litres drops down the credits you can achieve.

UnitsBase1 credit2 credits3 credits4 credits5 credits
Litres per minute12 ℓ9 ℓ7.5 ℓ4.5 ℓ3.75 ℓ3 ℓ
BREEAM flow rates taps

Finding a tap that produces a flow rate of 3 litres/min is a stress-free exercise. Dolphin’s DS112 slimline wall mounted tap reaches a 3-litre flow rate per minute, making it an Outstanding BREEAM performance component. Do you want an even lower tap flow rate? There are taps in our range that can produce as little as 2 litres or 1 litre should you intend to aim for an Outstanding rating.

Watch this video showcasing different aerator features, including water-saving flow rates, that you can choose from as options.

BREEAM Toilet flush volume

Most commercial washroom toilets come standard with a dual flush volume, for example, 6/3 or 4.5/3 (litres). BREEAM has set aside 5 credits up to a 3 litre effective flush volume.

UnitsBase1 credit2 credits3 credits4 credits5 credits
Flush volume in litres6 ℓ5 ℓ4.5 ℓ4 ℓ3.75 ℓ3 ℓ
BREEAM flush volume formula

But how do you calculate the effective flush volume? Use this simple formula as an example of how to calculate the effective flush volume:

BREEAM Urinal flushing

What’s interesting about the urinal flush volume is the ability to score 0 litres. To achieve 0 litres, this means implementing waterless urinals with no flushing mechanism and no water to flush.

Before raising your eyebrows at the thought, waterless urinals are quite common and the secret to maintaining a hygienic washroom with this component is the urinal replacement cartridge. The cartridge acts as a funnel to allow liquid to flow in and plays a role in sealing up unpleasant smells with its gel formula.

If for example, a urinal uses up to 1 litre of water for a flush, then a score of 4 credits can be awarded.

UnitsBase1 credit2 credits3 credits4 credits5 credits
Urinal (1 urinal only)Litres/bowl/hour10 ℓ8 ℓ4 ℓ2 ℓ1 ℓ0 ℓ
Urinal (2 or more)Litres/bowl/hour7.5 ℓ6 ℓ3 ℓ1.5 ℓ0.75 ℓ0 ℓ
BREEAM Shower flow rate - Dolphin DB3905 Shower Set

BREEAM Shower flow rate

If a commercial washroom has an end-of-trip facility or an area for showering, then a water flow rating would apply to the showers.

Look at a practical example in the graph showing a flow rate of 6 litres per minute: a user turns a shower on at the maximum pressure capacity, but the flow restrictor restricts the flow at 3 bar 5.7 litres per minute. The flow restrictor in the overhead shower (or handheld shower head) restricts the water flow, thus saving water.

UnitsBase1 credit2 credits3 credits4 credits5 credits
Litres per minute14 ℓ10 ℓ8 ℓ6 ℓ4 ℓ3.5 ℓ
DB3001 BREEM shower flow rate

To achieve 5 credits, the assessor would look at the flow rate at 3 bar up to 3.5 litres per minute.

BREEAM Greywater/rainwater

Greywater/rainwater is calculated as a percentage of a urinal or WC flushing. Up to 75% of recycled water or non-potable water achieves 5 credits. This type of water is not suitable for drinking, but depending on its quality, it can be used for many other purposes.

UnitsBase1 credit2 credits3 credits4 credits5 credits
Percentage of WC/urinal flushing demand met by using recycled non-potable water0%0%0%25%50%75%

How do BREEAM assessors calculate the final score?

BREEAM assessors have a spreadsheet form (referred to as a WAT 01 calculator) to enter all the information on your water components including, but not limited to:

  • Type of water component (taps, toilets, showers etc.)
  • Number of the water components
  • Flow rates
  • Flush volumes

WAT 01 is an assessment method used to calculate the water efficiency and consumption in a building, measured in litres per person per day.

The BREEAM water consumption scorecard contains 1 – 5 credits, and scoring 5 gives you an Outstanding BREEAM rating. The calculator also compensates for even lower flow rates than the BREEAM standard should other water components in the calculation have a higher flow rate.

Going above and beyond

Remember, the BREEAM flow rates and flush volumes are the standard litres to achieve, but it is more beneficial if you can achieve less. If the flow rates or flush volumes are lacking in some areas but are exceeding the standard in others, the potential to achieve a higher score is still possible. At the end of the day, it’s about how much water gets used and how much gets saved.

Start your green building rating journey by viewing Dolphin’s sustainable commercial washroom products that meet the BREEAM flow rates and flush volumes you want to achieve.

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