In the last few years, Part G Building Regulations have changed for all new builds, extensions and conversions. Now, if you’re a property owner or building developer, you’re legally required to prove that your property is water efficient. This means using no more than 125 litres of potable (drinkable) water per person per day. Some areas, such as London and other parts of the South East, set more stringent water consumption rates, going as low as 105 litres a day.

In all cases, to make these calculations experts need to consider information about baths, showers, toilets, sinks, washing machines and dishwashers. 

What is a Water Efficiency Test?

Water efficiency testing is all about evaluating how well a build conserves water. The evaluation must be passed before the property can legally be sold, as per Part G of the national Building Regulations To make the calculation, our experts consider factors such as:
  • The flow rate of the taps and showers, including any restrictors that may have been installed
  • The flush capacity of all the toilet cisterns
  • The water capacity of any baths
  • The specific amount of water consumed by any installed washing machine 
  • The specific amount of water consumed by any installed dishwasher
  • The efficiency of any installed water softeners
  • The effect of any installed harvesting systems for rainwater or greywater 
These evaluations should be done twice: once at the design stage and again on completion. For the former, it’s important to have them done early, in order to prevent the fitting of inefficient features which would make the build fail its water efficiency test.

Why is Water Efficiency Testing needed

With a rise in energy wastage in recent years, the government (national and local) are putting more pressure on property owners and building developers to be as energy-efficient as possible. This is multifaceted, but water output is an important factor in this. 

Non-compliance with water efficiency measures will negatively affect SAP calculations, so the government can ensure that any inefficient new build, extension or conversion won’t be viable for sale. As we know – properties can’t legally be sold unless they pass their SAP calculations.

When do Water Efficiency Calculations need to be made?

Part G Water Calculations should be made twice: once at the design stage and again on completion.

It’s important to have them done early on in order to prevent the fitting of inefficient features which would make the build fail its SAP calculations. For example, certain taps are more efficient than others, and you might think twice about installing the less efficient types if your build is already close to the limit. We can help you with suggestions about how to make your build more efficient, but that’s much easier to do earlier on, as we emphasized with SAP calculations.

Water Efficiency Calculations with Purple Energy

Choose Purple Energy for your water efficiency testing and rest assured of a seamless process. Our teams take pride in providing a turnkey service, working efficiently to get the calculations done with minimal input required from the client side. 

Our experts operate nationwide and are well experienced in conducting Part G Water Calculations. We simplify the process as much as possible to ensure we get the right information to keep timelines and costs down.

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If there is anything you feel unclear about or you simply want to speak to one of our team members, don’t hesitate to give our office a call.

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    Frequently Asked Questions

    To make things easier for you guys, we have a couple of common questions that we receive from clients.

    Using no more than 125 litres or 105 litres of potable (drinkable) water per person per day, depending on the level of the build.

    If your build is water compliant, it means it meets the requirements of Part G of the national Building Regulations or any localised requirements that mnight be in place.

    Water efficiency is measured in litres per person, and it’s all about how well a building conserves water. Generally speaking, a water efficient  property will have efficient water fittings, flushers, and a bath which isn’t excessively big. 

    This depends on timings. If the calculated water usage is too high at the design stage, we can advise on different water fittings like showers and taps with reduced flow rates, or draw up a set of design parameters to help you source compliant water fittings later down the line.

    If a building fails its water calculations after it has already been built and all water outlets are already in place, we can still help you to achieve compliance, but this will be through careful selection and installation of flow restrictors to showers and taps.

    water efficiency calculations