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

Why use Business Focused Maintenance?

Why do we do maintenance? Is it to keep our assets in optimum working condition? Do we do it to make the equipment last longer? Perhaps the main goal is to prevent failures? If it is for any of these reasons you may find that you are working to an outdated ethos…

BSRIA has recognised and employ a more pragmatic approach for today’s business needs. BFM recognises that the building services’ equipment is installed to provide a service, thereby allowing a business function to be maintained. It analyses the business needs and consequences of failure first and foremost. This ensures that business function is maintained with the minimum of intrusive maintenance to minimise maintenance induced failure, otherwise it is traditionally assumed that the built environment’s asset failure follows the bathtub curve below.

BFM

There are standard specifications for maintenance within the building services industry that have been updated over the years such as SFG20. This is used by many organisations to enable them to tender for outsourced maintenance on a like-for-like basis. The main drawback from this approach is that the maintenance delivered would be generic across the site. This can increase costs and/or reduce the availability of human resources. Couple this with the often-quoted statistic that “70% of failures are due to ineffective maintenance” and it begs the questions to be asked over purely time-based PPM frequencies.

BFM recognises that the need for maintenance generally arises from business needs such as

  1. Complying with legislation
  2. Minimising health and safety risks
  3. Minimising business risks
  4. Managing business continuity
  5. Responding to business and customer requirements
  6. Adding value as part of the business process
  7. Reducing overall business costs
  8. Maximising whole life cost
  9. Increasing asset / system availability
  10. Increasing operational up time

Users of BFM – first published as a BSRIA Guide in 2004 – have demonstrated increased system availability and greatly reduced costs. There is a structured, six-step process to follow where the client and BSRIA work collaboratively to

  1. Assess business needs and consequences of asset failure
    • The goals of the business and the needs of the end users are assessed to ascertain which assets are crucial, and therefore the impact on the business of assets failing. The structure of BFM allows for this task to be done as objectively as possible and logged on a numeric scale of 1-10. 1 is a low consequence and 10 is a high impact on business continuity.
  1. Document functional block diagrams and assess functional resilience
    • review the systems and assess their ability to continue to meet the needs of the business when a failure occurs.
  1. Assess asset condition
    • A full condition survey as per BG 35/2012 taking into account all relevant influences on an assets condition, to provide a remaining life expectancy.
  1. Calculate likelihood of failure
    • converts the alpha-numeric score from tasks 3 and 2 to a 1-10 score via conversion table 6 in the BFM guide BG 53/2016.

BFM1

5. Calculate BFM score

    • combine the score from task 1 (BC) with the number calculated in task 4 (L) to give a BFM risk score on a scale of 1-100.

BFM2

6. Review of PPM tasks and frequency

    • Apply scores to the agreed level of risk set by the organisation. From this a revised maintenance schedule can be drawn up. BG 53/2016 suggests the following;
      • 1-9 Discretionary maintenance for non-critical assets
      • 10-40 Legal compliance and sector specific requirements
      • 41-100 Maintenance to provide the greatest level of confidence in asset reliability, performance and availability.

bfm5

Whilst every job is different, an indicative timeline can show you that BFM can very quickly make it’s impact on businesses.

The business-focused maintenance methodology challenges the planned preventative maintenance frequency of building services plant. The assessment methodology takes into account plant history (age, condition, failure history, plant loading, and maintenance history), the number of standby plant items (redundancy), and the level of resources available.

Many of the intrusive maintenance tasks can be replaced by Condition Monitoring (CM) which in turn leads to Condition Based Maintenance (CBM). The actual practice of CM is far quicker in terms of man hours than time-based PPMs and often involves zero down time to the asset and therefore no impact to the business. In addition to the usual array of gauges on an asset or its BMS sensor display that can be used to monitor plant performance, common CM methods include thermal imaging, vibration monitoring, acoustic emission monitoring and lubricant analysis.

Regular use of these methods at appropriate intervals can be far more cost effective than regular time-based generic intervals, whereas for non-critical plant, the most cost-effective maintenance methodology may be to run-to-failure. By applying the BFM methodology, you can be confident that you have selected the most appropriate maintenance technique for the services in your building.


This article was written by Nick Blake – Principal FM Consultant at BSRIA.

For more information about our research on maintenance and facilities management, please contact: consultancy@bsria.co.uk

To download our publication on Business Focused Maintenance (BG53/2016):
please click here>>

BSRIA's publications on maintenance and facilities management

 

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.

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