Take the pressure off water and energy

David Rhodes, Technical Manager of Albion Valves, explains the urgent need to design for water and energy efficiency – and highlights pressure reducing valves (PRVs) as part of a cost-effective technology to save these critical resources.

Over the past twenty years, building services engineers and contractors have focused on reducing energy consumption in the design and operation of HVAC systems. Legislation such as Part L of the Building Regulations and Minimum Energy Efficiency Standards (MEES) are just two of the drivers setting targets on carbon emissions and energy use in all buildings.

Now, there is a second factor in the spotlight for savings and efficiency: water. In Northern Europe’s hotter summers, droughts are a growing cause for concern. The UK uses around 14 billion litres of water per day, but the government estimates that this will rise to 18 billion litres by 2050. We must reduce that figure to prevent severe shortages in the next decade.

The government published its Plan for Water in April 2023, outlining how it will tackle rising demand and the hazard of future droughts. It wants to reduce water use per head of population by 20% by 2030. This means cutting water usage in homes and other buildings. One proposal in the Plan for Water is to expand the EPC (Energy Performance Certificate) issued to domestic and commercial buildings to include a grade for water efficiency.

With the government seeking to cut water consumption along with ever-tighter energy targets, it’s clear that engineers and installers must be ready with measures to help achieve both. In addition, transporting water around a building can be an energy-hungry process, so technologies that can make that process more efficient while reducing water waste should be high on people’s agenda.

Albion’s wide range of valves has been designed and manufactured to support the effective and efficient operation of hydronic systems in commercial buildings and dwellings. Our experience working with engineers and contractors who deliver these systems means that we have developed products that are cost-effective and straightforward to specify and install. We have recently expanded our range of pressure reducing valves (PRVs) to include ½” to 12” (DN15 to DN300), and pressure ranges PN16, PN25, and PN40.

PRVs are an integral part of a balanced system to achieve energy efficiencies within buildings and ensure the effective distribution of pressurised water. When used with hydronic valves, it is possible to attain the maximum cost-effective usage in distributing water within a system.

A 2022 UK government study into proposals for water efficiency labelling highlighted showers, toilets and kitchen and bathroom taps as significant water users in households and other buildings. PRVs can be applied to reduce water pressure, helping regulate water volumes and reducing water waste when outlets are in full flow. It may seem like a small step, but controlling water pressure this way can save significant amounts.

Take a tap outlet which is open for five minutes at 5 bar. It will pass around 15l to 20l per minute. However, if a PRV is applied to reduce the pressure to 3 bar, the volume of water from the tap drops to 12l to 15l over the same period, a saving of 25%. This works well in domestic settings, but if we extrapolate that to washroom sinks around a typical office building, it is easy to see why PRVs are invaluable for helping to reduce water waste.

PRVs also play an important role within tall buildings, where the design intent for water distribution around the building can vary; these systems will often include booster sets.

The building distribution system is typically divided into risers and branches. With risers, the geodetic height has to be overcome, and the water distributed to the different floors. The branches will then distribute the water to each of the terminal points.

These branches often form part of a main branch, thus creating zones. To equalise the pressures throughout these zones, pressure reducing valves are essential.

Although they are simple in principle, PRVs must be specified correctly, based on flow and pressure, to make the most of their benefits. Therefore, avoiding selecting a PRV based solely on the line size is essential. Instead, the specifier should size a PRV to obtain a flow velocity across the seat between 1m/s and 2m/s for domestic applications.

Specifiers should always check the manufacturer’s technical documentation, such as cavitation charts and / or flow volume charts (provided with Albion’s PRV range).

Cavitation charts are important to determine the pressure reducing capabilities of the valve. A general rule is to reduce the pressure by no more than 3:1 in a single stage. In addition, using the flow volume charts will aid the size selection of the valve.

Correct sizing is vital to optimise performance and avoid damage to the valve. For example, a PRV which is too large will continually operate nearer to its ‘shut’ position, leading to erosion of the seat and eventual failure. On the other hand, if the valve is too small, then the volume of water rushing across the seat will cause unwanted noise, such as hammering.

There are two main types of PRV: direct acting and pilot operated. Both are designed using a pressure-loaded diaphragm, and selection depends on project requirements. For example, direct acting PRVs are best used for small loads. We see them widely applied on individual or small numbers of terminal units, such as apartments where taps, showers and baths are distributed throughout the property.

They generally have a compact size with a low price point and are simple to install. However, because of their size, they have a relatively low flow capacity and a higher proportional offset, or variation, from the set pressure.

Pilot operated PRVs are used for larger loads where close pressure control is required. They are often found in commercial or multi-residential properties, industrial buildings, and distribution systems.

This type of PRV can provide accurate control because the pilot valve is significantly smaller than the main valve, so it responds very quickly to minor variations in upstream load. With the addition of a trim to control the response time of the valve, the main valve has a lower proportional offset and therefore delivers a more constant downstream pressure.

Albion provides a range of PRV sizes and materials suitable for small domestic projects up to large commercial systems to ensure that contractors have everything they need for a successful installation.

Water shortages in the UK are a pressing issue affecting us all. Research from Kingfisher (owner of Screwfix) carried out in April 2023 shows that seven regions in England face ‘severe water stress’ by 2030. The government’s Plan for Water suggests that it won’t be too long before planners demand that new developments are ‘Water Neutral’ and Carbon Neutral.

The increasing focus on managing our water use in buildings points to the use of PRVs in combination with other control valves to aid both pressure and flow control to manage hydronic systems as key to delivering ‘water efficient’ homes and commercial buildings.

In addition, over the next five years, legislation and government policy will drive the adoption of alternatives to gas boilers, such as heat pumps or district heating, in domestic and commercial buildings. So, this is an excellent time to consider valve technology within those systems as highly effective solutions for achieving energy and water efficiency.

For over forty years, Albion Valves has helped engineers and contractors deliver optimised water-based systems. Our continually developing range of products and our in-house expertise enable Albion to supply a complete, quality valve solution alongside excellent cradle-to-grave technical support and service for the industry.

To view Albion’s Pressure Reducing Valve range see here or for more information