Maintenance of drainage systems to prevent flooding and water pollution

By David Bleicher
BSRIA Publications Manager

Every building has a drainage system. In fact, most have two – a foul drainage system that takes waste from toilets, showers etc. and a storm/surface water drainage system that takes rainwater from roofs and paved areas. Older buildings may have a combined system, and in some locations the infrastructure buried under the street is a combined sewer – a legacy from the pioneering days of city sewerage systems.

As with maintenance of any building services systems, the first step is to know what you’ve got. Every site should have a drainage plan, showing which drains are located where, what direction they flow in and what they connect to. If there isn’t one, it’s not hard to create one – even though the pipes are buried, there’s plenty of evidence above ground in the form of manholes.

When there is a drainage plan, it’s worth checking how correct and up-to-date it is. Sometimes, the exercise of doing this brings up evidence of mis-connections, such as a new loo discharging into a storm manhole. It’s also worth marking drain covers with the service (F for foul or S for storm) and a direction arrow.

Drainage manhole over showing 'S' arrow to indicate storm drainage and direction of flow.

In foul drainage systems, the biggest headaches are caused by things going down the drain which shouldn’t – like wet wipes, sanitary products and hand towels. So the best form of preventative maintenance is to keep building occupants informed, with polite notices and clearly-marked bins in strategic places. Then there is the fats, oils and greases (FOG) that go down the plughole in catering establishments. If these find their way into the drains and sewers, they’re pretty much guaranteed to solidify and cause blockages – sometimes known as ‘fatbergs’. That’s why there should always be an interceptor in place, also known as a grease trap. This needs maintenance – the generic frequency for cleaning out a grease trap, stated in SFG20 (a common approach to planned preventative maintenance), is monthly. But this will be highly dependent on how the facility is used.

If blockages go unchecked, they may also go unnoticed. That is until sewage starts backing up into the building, or overflowing into storm sewers, which eventually discharge into lakes and rivers. These are delicate ecosystems, and the introduction of detergents and faecal matter can be very harmful to aquatic life and of course humans.

Rain, can pick up contaminants from both the air and the land, so once it has reached a storm/surface water drainage system, it has picked up dirt, oil and chemicals from air pollution, roofs and paved areas. Traditional systems have no means of dealing with this, and also must be sized for occasional extreme storm events, so the pipes are very large and mostly used at a fraction of their capacity. Sustainable drainage systems, or SuDS, attenuate the flow of rainwater to watercourses and emulate the way natural ecosystems treat this water. But they need maintenance. For example, any tree routes that could block a soakaway should be trimmed annually, and green roofs may require weeding on a weekly basis during the growing season.

For more information on the maintenance of drainage systems, please explore the BSRIA Information Service

Safety in Building Services Design

This is a guest post by Richard Tudor of WSP

This is a guest post by Richard Tudor of WSP

Space, and the cost of providing space, for plant and building services  distribution is at a premium and designers often come under pressure to reduce the spatial requirements for building services installations. In order to discharge their obligations, designers must take care to provide safe means of access for installation, maintenance and equipment replacement.  In addition designers need to be aware of the regulations and legislation requirements that a design may impose on the installer and end user as a design solution can often impose additional legal

responsibilities, particularly in undertaking associated operation and maintenance activities. However, the active and continuing attention to safe access issues, throughout the design stages, is not always achieved as the designers’ attention can often concentrate on what is perceived to be more immediate concerns.

BSRIA’s publication Safety in Building Services Design BG55/2014 has just been published which provides guidance on designing for safety in both new and refurbishment projects.

The publication is aimed at designers and includes information on:

  • relevant legislation including CDM
  • hazards and risks including managing risk in the design process
  • understanding space requirements and access provision
  • designing for maintenance
  • plant room design
  • communication of risk information including representation of risk information on drawings

BG55/2014 Safety in Building Services Design

BG55/2014 Safety in Building Services Design

However, the diversity in type, configuration and possible location of plant, means it is not possible for this publication to give definitive guidance for all installations.

The publication provides a practical guide to assist the design process, aid design reviews together with providing a better understanding in designing for safety.  For example, included in the publication is a checklist on the considerations in designing for health and safety which can be used as part of the technical design quality review process.  In the pdf version of the publication this is included in an editable Excel format. Influencing factors, considerations and space requirement data useful in the design decision process with respect to providing safe access are highlighted in the publication.

The poor provision of safe access for maintenance could result in an increased likelihood of cutting corners or omission of maintenance and repair activities. This in turn, could result in building services failures that could adversely affect safety, legal compliance, productivity and quality of the environment.

BSRIA launches a new course on the 12th November 2014 providing guidance in designing for health and safety in the space planning of building services with respect to operation, maintenance and plant replacement. The course is intended for professionals involved in the design of building services but is equally relevant to contractors and other professionals within the industry. Young engineers in particular would benefit from the course.

On completion of the course delegates will be able to:

  • understand the specific considerations with respect to designing for safety for building services
  • identify discipline specific considerations in designing for safety
  • challenge designs in relation to health and safety in the design, construction and operations of building services so as to improve performance
  • understand relevant H&S legislation, codes of practice and guidance
  • understand the relationship between building services design and maintenance operations
  • understand the management of hazard and risk together with control strategies
  • locate information relating to health and safety to assist in design process
  • understand the consequences of failing to manage health and safety effectively
  • understand the importance of communication and provision of information in the design process

Richard Tudor is a Senior Technical Director at WSP and has been an integral part of the WSP Group Technical Centre for over 14 years. His responsibilities include technical quality, specification development, technical knowledge management, delivering training, designing for safety, providing technical support, and improving project delivery.

The selection criteria of refrigerants

Salim Deramchi, Senior Building Services Engineer at BSRIA

Salim Deramchi, Senior Building Services Engineer at BSRIA

This is part two of a three part series from Salim. You can read part 1 here

There is no general rule governing the selection of refrigerants, however there are of course the five classic criteria and those are:

  • thermophysical properties
  • technological
  • economic aspects
  • safety
  • environmental factors

However, in addition to these criteria, others have to be considered such as local regulations and standards as well as maintainability and ‘cultural’ criteria associated with skills to support the units, application, and user training requirements.

The best approach when presenting evolution and trends is certainly the per-application approach. The desirable characteristics of “ideal” refrigerants are considered to be:

  1. Normal boiling point below 0°C
  2. Non-flammable
  3. Non-toxic
  4. Easily detectable in case of leakage
  5. Stable under operating conditions
  6. Easy to recycle after use
  7. Relatively large area for heat evaporation
  8. Relatively inexpensive to produce
  9. Low environmental impacts in case of accidental venting
  10. Low gas flow rate per unit of cooling at compressor

The choice of alternative refrigerants should involve a review of recycling or disposal of refrigerants. You must decide which criteria for the ideal refrigerant is of most importance to your organisation. It must be considered that the operation phase is the key factor when determining the environmental impact of the various refrigerants as there is less impact to the environment in the production and disposal stages. As an example, supermarket retailers are steadily moving away from long-established HFC refrigeration systems.

Decision making for new refrigeration plant using refrigerant alternatives such as ammonia, CO2 or hydrocarbons, which have comparatively little or no impact on global warming and zero impact on ozone layer, should consider not only the impact on the environment but the additional required skills to maintain (Ko Matsunaga).

You can  find out more information in BSRIA’s library

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