Naylor

Clay- the ideal material for sewer pipes

Edward Naylor, Chief Executive, Naylor Drainage Ltd, supplier of clay pipes, plastic ducting, land and twin wall drainage to EH Smith. The thing about drainage materials is that they are generally out of sight and, for many, out of mind. This is certainly true of house-buyers, most of whom will studiously inspect every facet of a show-home but not once enquire what the underground drains are made from. Yet a property’s drainage is far from unimportant. However, the differing requirements of property owner and installer may not be aligned. The property owner is interested in the long-term perspective: a durable infrastructure which is up to the challenge of maintenance procedures such as rodding and jetting. The installer by contract is interested in the short term- product lightness and ease of handling. Although for years the construction industry enthusiastically embraced PVCu, there are shortcomings such as the material’s lack of inherent strength. In particular, bedding is critical to PVCu pipes as the backfill forms an integral part of the structural integrity of the pipeline. A PVCu pipeline will flatten under relatively light loads unless it is fully and carefully surrounded by a bed of single-sized pea gravel or similar material. This has two important implications: firstly, significant quantities of imported aggregate are needed for a PVCu drainage system, and secondly, plastic pipe systems are vulnerable to poor site practice. In contrast, clay pipes have inherent high structural strength and rigidity, and can often be laid directly on a trimmed trench bottom, with zero or minimal bedding. This significantly reduces the use of scarce and expensive aggregates and minimises site excavation. Even bedded correctly, plastic life expectancy is limited. Plastic progressively weakens in service: thermoplastics such as PVCu and HDPE lose half their initial strength over the first 2 years and 80% over the first 50 years. They are also vulnerable to pipe-cleaning operations, particularly rodding and high-pressure jetting. In contrast, clay pipes have excellent abrasion resistance and retain their strength: a 100 year-old clay pipe will have the same strength as on day one. Indeed, clay is truly tried and tested: clay pipes have been proven over hundreds and even thousands of years of service, and for design purposes, they can be assumed to have an infinite life. Given these major performance advantages, one would be forgiven for expecting a huge premium to attach to the use of clay. But once factors such as bedding are taken into account, the on-cost is often minimal if not non-existent. Perhaps the next generation will have cause to regret the penny-pinching of many who are currently responsible for drainage material selection? For further information contact Edward Naylor on 07778 472454; edward.naylor@naylor.co.uk