Most self-builders expect initial design discussions to revolve around architectural styling, interior layout, or even energy efficiency. Few people expect a detailed conversation about toilet flush volume, shower capacity, or shower flow rate. But these are questions that need to be addressed in order to comply Building Regulations and approved document g.
Without understanding its requirements you risk choosing bathroom and kitchen fittings that fail to meet the standards. And if the penny doesn’t drop until it’s fitted, changing specifications can be both expensive and frustrating.
In fact, the approval document G is quite easy to satisfy, if it is considered at the beginning of the project. Understanding what it covers, when it applies and how compliance is assessed will help avoid unnecessary surprises when it comes to final approval.
What exactly is approved document G?
At first glance, Approval Document G (often referred to as Part G), looks like little more than a plumbing standard. In fact, it has a much wider influence on the design of the new home and how it will function. As an approved document it sets out pre-approved methods of compliance for sanitation, water efficiency, hot water safety and washing facilities, affecting everything from the specification of sanitaryware and hot water cylinders to the calculations required before building control projects are signed off.
Part G is generally one of the least discussed parts of the Building Regs and, as a result, perhaps the least understood. This is not because it is particularly complicated, but because most homeowners are unaware of its importance and how it influences early stage design decisions.
Approved Document G is a formal title Sanitation, hot water safety and water efficiency. Not exactly a delicate title, and more importantly doesn’t show its influence on the modern home.
The document is divided into six main areas including water supply, water efficiency, sanitary facilities such as WCs, washing facilities and the bathroomas well as food preparation areas, The kitchen sinkand safe production and storage of hot water. The overall aim is to ensure that the home is hygienic, safe to use and makes good use of one of our most valuable natural resources.
Although do-it-yourselfers think of Part G as something for plumbers, most important decisions are actually made much earlier. ArchitectBuilding Designers and Building Services Engineers. By the time a plumber starts, many key compliance decisions should already be made.
Importance of water efficiency calculations
The part of Approval Document G that generates the greatest number of questions is the water efficiency requirement for new dwellings.
Every new house should be designed to limit the estimated water consumption to no more than 125 liters per person in general. In parts of the country where water scarcity is a concern, local authorities have adopted strict planning policies to reduce the requirement to around 110 litres.
The calculation is not based on measuring how much water you actually use, so you don’t have to worry about the faucet suddenly turning off. Instead, it predicts potential consumption using a standardized method based on each water-using device installed in the property. This includes toiletFaucets, showers, baths and even appliances like washing machines and dishwashers. If Rainwater harvesting or greywater recycling systems are incorporated, this can improve the overall result.
In practice, water efficiency calculation is a similar design tool SAP calculationsWith the aim of having a positive impact on the efficiency of our homes.
Approved document G and hot water safety
Approved document G contains several important requirements for the safety of hot water. Stored hot water is usually maintained at a temperature of around 60°C to minimize the risk of Legionella. However, water stored at this temperature can cause injury by scalding, so new homes require a thermostatic or mixing valve for showers.
This mixes hot and cold water before it reaches the faucet, allowing the cylinder to stay warm while delivering water at a safer temperature.
Part G also rules unvented Hot water storage Systems Since these cylinders operate under main pressure, they require safety devices to control the pressure and safely drain the water if a malfunction occurs. Standards are specific, so installation and commissioning is best carried out by a suitably qualified and competent installer.
How to comply with approved document G
Small choices can have surprisingly big results
A common misconception is that Choosing bathroom fittings Mostly an aesthetic decision. A rainy rain Sounds luxurious with a very high flow rate, but if it is installed in a new build property, it can consume a significant proportion of the water consumption target. Decisions such as choosing a WC with a larger flush volume instead of a dual-flush model will also have implications that can collectively increase the calculation beyond allowable limits.
The last thing you want is to fit a beautifully designed bathroom which ultimately fails the final mark when the building control officer checks the fittings against the original water efficiency calculation. The result will undoubtedly be more work, and possibly fit a different bathroom that is no longer so pretty.
Fortunately these problems are not that difficult to solve, provided compliance is understood at the design stage, and upgrades are not made without thoroughly checking their usage levels.
Don’t think about Part G in isolation
Like most other approval documents, Part G overlaps with other parts of the regulations. its relationship with Approved Document L Perhaps most obviously, because reducing hot water consumption also reduces the energy required to heat it, helping to improve overall energy efficiency.
Bathroom ventilation comes under Approved document fwhen Drainage Covered by design Approved Document H. Addressed by accessibility needs in bathrooms Approved Document MAnd electrical installations come in around the shower and bathroom Approved document p. It can all be rather confusing.
Fortunately, competent designers will consider all of these documents together, rather than treating each one independently. In practice, moving a bathroom can affect drainage gradients, ventilation routes, electrical zoning, accessibility and water efficiency calculations, so it’s always best to check design implications before making changes.
Does Part G apply to every project?
The simple answer is no. For a new build home, or a new residence created from it transformationThe requirements of Part G apply in full.
Extensions are slightly different. If you are adding additional accommodation to an existing home, you will not normally need to demonstrate compliance with the 125-litre water efficiency target. However, any new sanitary accommodation, kitchen or hot water system will still need to comply with the relevant sections of Part G.
Bathroom renovation is different again. If you are replacing an existing bathroom within an existing house, you will not need to complete a whole house water efficiency assessment as the Building Regulations recognize that it is not always practical to bring an old property up to current standards.
However, all new work still complies with relevant parts of Part G, such as safety standards. For example, replacing an old vented cylinder with an unvented system requires modern safety requirements.
How compliance is checked
Unlike some aspects of the Building Regulations, Part G is not assessed during a single inspection. Compliance begins in the design phase when product specifications are chosen. Water efficiency calculations are usually prepared, and once construction is underway, Building Control will inspect the plumbing installation.
At the end of the project they will ask for supporting documentation that the installed products achieve the water consumption determined by the water efficiency calculation. If an unvented cylinder is installed, they will also ask for a commissioning certificate. As you might expect, changing products without updating the supporting calculations can therefore become a compliance issue upon completion.
Responsibility for Part G is shared
There is no such specialist Part G consultant and responsibility is usually shared between the design team, and ultimately the trade on site.
The lead designer will usually coordinate compliance and depending on who is in the hot seat the water efficiency calculation is often done by a SAP assessor, energy consultant or building services designer.
Ultimately, responsibility rests with whoever works on the site. For do-it-yourself projects, and especially those that are self-managed, it’s a good idea to make sure everyone is working to the same specifications and that product choices follow the assumptions made in the water usage calculations.
Will the approved document G change anytime soon?
While the main requirements of Approved Document G have not changed much in recent years, water efficiency is becoming increasingly important.
Population growth, climate change and increasing pressure on water resources mean that we should expect more stringent consumption targets in the future. More emphasis will therefore be placed on the efficiency of sanitaryware, leakage reduction and the use of alternative water sources such as rainwater harvesting and greywater recycling.
Approved document G is not a regulation that excites most self-builders because there are no advanced technologies to imagine. However, there are many traps that can catch people if they are not fully considered early in the design process.
From a self-builder’s point of view, my advice is simple. Know that there are needs but trust that a competent design and construction team will take care of them.
And before splashing out on the size of a beautiful spa bath, small swimming pool, check the water efficiency calculations, otherwise you’ll find building control asking uncomfortable questions just when you want to move in.
