Traditionally, HDPE and in particular PVC systems have accounted for a high proportion of above ground drainage systems, the remaining share predominantly being split among metal products, but recent claims regarding combustibility of plastics has lead to a heightened interest in more robust, products to combat the issue.

Whilst the risk of fire raises alarm bells for any designer, so do perceptions of the increased costs involved in purchasing, installation and maintenance of a non combustible system. This has prompted increased interest in the value of procurement on the basis of whole-life rather than lowest tendered cost.

However, M&E consultants wanting to compare material performance don’t have it easy, faced with a tide of information containing varying, some say inconsistent claims from manufacturers. Whether considering durability, cost, health and safety, recyclability, speed of fit or a combination of factors, product functionality and value can be hard to assess objectively. Inevitable prejudices built up over time have tended to pigeonhole materials with particular environments and project types, and lobbying in favour of specific materials has not always put a balanced view. In this light, independently produced reports carry much more weight when assessing products as they are inclined to offer an unbiased ‘warts and all’ review, rather than just a list of benefits.

As an example, BSRIA has produced a report, which set out to identify innovative means of M&E drainage installation. Its data sheet 5.11.2 confirmed that overall fitting time for a section of a vertical soil drainage system in stainless steel was a fraction under 40 percent quicker than one in lightweight cast iron, installation time for pipe sections and branch fittings for the stainless steel product taking less than 14 percent of that for the traditional system.

The Building Performance Group also undertook a whole-life cost assessment of the four primary internal waste drainage systems in a model project of an acute hospital. The systems assessed were stainless steel, lightweight cast iron, solvent-weld PVC, and a high-density polyethylene (HDPE) fusion welded system. It considered which had the lowest capital costs, lowest cumulative costs over 30 and 50 year assessments, and lowest net present values (at discount rates of 3.5 percent and six percent). Stainless steel offered the best value by all measurements.

Contemporary construction techniques such as off-site prefabrication and cutting have tended to work in favour of PVC. With such construction, use of heavy materials and awkward fittings is impractical. The stainless steel product assessed, Blücher EuroPipe, is push-fit and straightforward to install, in many cases only requiring one fitter. This makes it ideal where installation times are limited or solvent welding not ideal, such as retail or residential refurbishments (high rise in particular). In the London Borough of Newham, Arup Building Services Consultants recently carried out a complete refurbishment of 56 flats over 14 floors and specified stainless steel for the drainage refit. Most of the work was carried out without need to relocate the residents. Conditions were cramped, so solvent welding and bulky cast iron were ruled out. Time constraints, imposed to minimise disruption to tenants and to accommodate tight overall refit schedules, gave stainless steel considerable edge over all other materials considered.

Mike Carter of Arup commented: “Only 12 flats were left empty for families to move into while kitchens and bathrooms were re-fitted, but all drainage was renewed with residents in occupation. Stainless steel was chosen for its weight, speed of installation and ability to prefabricate key branches and junctions. No snap cutting machines were needed on site, something which, given the accessibility and size of the apartments, was out of the question. The bulky nature of mechanical coupling was avoided too, as was any solvent or fusion welding of plastics, the other alternatives initially considered. Availability of standard pre-cut pipe in a range of lengths from as short a section as 150 mm up to six metres also reduced the need for site cutting. Fourteen floors of a high rise is no small matter for any contractor, and the need for risk assessment of moving heavy materials with or without lifts was rendered unnecessary”.

When compared to any metal system, plastics have traditionally had the advantage when it came to the weight and cost of fittings. Products such as Europipe are sufficiently light to make handling just as easy as plastics, while being completely fire resistant and durable. Its fittings are produced from the pipe itself, so bespoke designs such as unique bends can be produced cost effectively in a very short time. Whilst initial purchase may be more costly, speed of installation combined with minimal maintenance and excellent whole life cost tips the balance in favour of fire-resistant stainless steel.

From an installer’s viewpoint, problems have been encountered when air testing cast iron. These include finding pinholes in fittings, failure of couplings, and cracked pipes, all potentially time consuming and expensive to rectify, and difficult to detect. Europipe’s fittings are individually tested, virtually eliminating air test failures, while cracking is not an issue.

Regardless of the preferred method of procurement, the relative cost of stainless steel continues to move in its favour, while continued improvements in manufacturing techniques enable quality standards to meet the most exacting specification. Fewer brackets and hangers are needed to support it, while a smooth internal bore is highly resistant to blockage. The product is also 100 percent recyclable. Even specific criticisms of cutting and teeing into an existing pipe run for example, have been answered with results which show that, using a retro fit coupler, the operation can be achieved in a matter of minutes.

Independent evidence points firmly towards stainless steel as an ideal fire resistant alternative to plastics, while stressing its lighter weight and quicker installation time when compared with cast iron. The product’s suitability for gravity and symphonic soil, waste, rainwater, vacuum and process waste water, as well as hot and corrosive liquids also adds to its versatility. Time will tell how quickly consultants, designers and installers will move towards using and specifying this contemporary drainage solution as a cost-effective, fire resistant alternative to plastics.

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