Setting the standards in drainage

Specifiers and installers of plastic underground drainage systems already know what benefits the material can offer. Lightweight, easy to install, durable and cost-effective, plastic has taken the underground drainage market by storm over the last 20 years. But the market is constantly changing. Frank Jones, director of the British Plastics Federation Pipes Group, explains the latest European legislation covering underground drainage systems.

The use of PVC in domestic and commercial drainage systems began around 30

years ago and has grown to dominate the market. In the UK, PVC now accounts

for around 85 per cent of the rainwater market and 50 per cent of the

underground drainage market (with 75 per cent of the 110mm pipe market). It

seems that the practical and competitive UK building industry puts cost and

performance first and this is where PVC wins hands down.

PVC has come a long way in the past 30 years. Innovations in both design and

manufacture have improved strength, durability and product choice. Improved

formulations with additional stabilisers can handle exposure to sunlight

without embrittlement and extreme and fast-changing temperatures.

Last year a new Euro Norm BS EN 1401-1:1998 covering PVC underground

drainage pipes and fittings in sizes from 100mm to 1,000mm came into effect.

The new standard raises a number of important issues for specifiers of

underground drainage systems and the British Plastics Federation (BPF) Pipes

Group is working hard to ensure that specifiers, merchants and installers of

underground drainage systems are fully informed about what the new standard

means for them.

BS EN 1401-1:1998 replaces parts of the existing British Standard BS 4660

and all of BS 5481. Pipes and fittings manufactured to the new standard will

be completely interchangeable with old products in terms of dimension. In

order to continue receiving exactly the same high quality product as

previously, specifiers should continue to identify ŒStiffness Class 4′ on

all specifications. BS EN 1401 does cover the use of a thinner grade of pipe

with reduced stiffness (stiffness class 2) in pipes with diameters of 160mm

and above than was permitted under the previous British Standards.

The BPF Pipes Group strongly recommends that specifiers continue to specify

stiffness class 4 because using Stiffness Class 2 pipes could cause costly

delays and problems on site because they require much more preparation and

bedding to give the same performance, even though they do technically comply

with BS EN 1401-1.

For the first time ever, the new standard also stipulates the specific

application areas where certain pipes can and cannot be used. It stipulates

that Stiffness Class 4 (equivalent to BS 4660 for 100mm and 160mm and BS

5481 for 200m, 250mm, 315mm and 400mm) or Stiffness Class 8 pipes and

fittings must be used if an installation is to comply with BS Codes of

Practice and resist long-term deformation.

Stiffness Class 2 pipes will need to be subjected to complex structural

design load calculation and expensive and time-consuming installation

techniques to achieve the same result.

For the first time, the BS EN 1401 defines two separate application areas

and the type of pipes and fittings that can be used in each:

– U: application area code for areas more than one metre away from the

building to which the buried pipe system is connected; and

– D: application code area for the area underneath and within one metre from

the building where pipes and fittings are underground and connected to the

soil and waste discharge system.

All pipes and fittings manufactured to BS EN 1401 will be marked with these

codes. Since Stiffness Class 4 or 8 pipes are suitable in both cases, they

will be marked ŒUD¹. The new European standard states that Stiffness Class 2

(SN2) pipes are totally unsuitable in areas where hot water discharge occurs

(D applications) and strongly recommends the use of Stiffness Class 4 or 8

pipes in these applications.

Specifiers of PVC underground drainage systems can start using the new EN

with immediate effect, retaining reference to the existing standards until

the changeover is completed in October 1999. The new standard refers to all

PVC underground pipes and most fittings from 110mm to 1000mm. Access

fittings and gullies will continue to be covered by BS 4660.

The BPF Pipes Group is made up of the UK¹s leading PVC pipe and fitting

manufacturers and covers rainwater, soil and waste and underground drainage


The group was set up to promote plastic and educate the building and

construction industries about the benefits of using plastic pipes and is

issuing a series of technical bulletins outlining the changes that the new

standards will bring about and what specifiers should know about them.

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