Without a water main, a water distribution system is incomplete.
Comprising a complex infrastructure of pipelines, pumps, storage tanks, valves and hydrants, a water distribution system needs robust pipes that can withstand internal and external pressure and corrosion.
This article discusses the best types of pipes needed for a water main.
WHAT IS A WATER MAIN?
A water main is the primary underground pipe in a water distribution system of a particular locality. It supplies water to other connected secondary pipes on the way to the consumers. These pipes are large diameter pipes laid within the public right of way and placed 1 to 2 meters below the ground surface to protect against traffic load and prevent freezing.
How does it work?
Also known as primary feeders, water mains take clean water from treatment plants through secondary pipes to homes; industrial and commercial activities and properties; and for firefighting requirements.
The community receives adequate water through the special arrangement of the water main, secondary feeders, other pipelines and fixtures designed to keep the water distribution system running efficiently.
TYPES OF PIPES
The primary concern for water mains pipes is the high cost of inspection and repairs. Thus, pipes for water mains are designed to be strong and reliable, ensuring longevity. These pipes not only withstand environmental conditions, internal and external loads but also operational conditions such as sudden and gradual water pressure fluctuations. Cast-iron pipes were originally used for water mains until the 1970s. Although durable, these pipes are brittle and have a short lifetime. They are subject to cracks and bending from exerted environmental and heavy-traffic pressure, and are susceptible to damage in freezing temperatures caused by expanding ice in the water mains.
Innovation in pipe manufacturing and pipe materials thus led to products and systems that replace the fragility of cast-iron pipes. Currently, the most common materials used for water main pipes and fittings are metal and plastic.
METAL PIPES
Ductile Iron Pipe Ductile iron pipes are stronger, more durable, and less brittle. Made entirely out of scrap iron and steel, these pipes have more flexibility and are resistant to shocks and vibrations. They even handle freezing temperatures better than cast-iron pipes.
Since ductile iron pipes are susceptible to corrosion, the inside of the pipe is lined with cement mortar to strengthen it.
Steel Pipe Steel pipes are stronger and lighter than cast-iron pipes and are ideal where large diameters pipes are required.
These pipes offer excellent resistance to internal pressure and pressure surges but are susceptible to atmospheric temperature changes which can cause the pipes to buckle.
An internal asphalt coating protects against corrosion, which affects steel pipes as well, and prevents against acidic water when the pipes are used for water mains.
The sheer strength of steel and resistance to breakage makes these pipes a viable option for water mains.
PLASTIC PIPES
High-Density Polyethylene (HDPE) Pipe HDPE pipes, manufactured from polyethylene resin, are a popular choice for water mains because of its durability and non-corrosive qualities. These pipes are highly flexible and resistant to fatigue—they can handle usual pressure and pressure from recurring surges which is common in any water distribution system.
HDPE pipes cope with high impact not only from traffic but also from soil movement, making these pipes suitable for earthquake-prone regions.
These pipes are invaluable for water mains due to the strong joints fused together with heat and pressure. The joint is stronger that the actual pipe and prevents zero water loss, an important aspect for any efficient water distribution system.
However, HDPE pipes have to be installed in trenches. The strength of the HDPE pipe against applied load is considered as part of the soil-pipe system where any failure of the pipe depends partially on the backfill and soil surrounding the pipe.
Polyvinyl Chloride (PVC) Pipe PVC pipes are widely used in new water main connections. However, PVC is one of the oldest synthetic material in use for many other applications.
PVC is thermoplastic and can be softened and molded. This means that PVC pipes are ideal for trenchless construction and installation. These pipes are extremely durable, and although the strength of the bedding is important, the strength characteristics of the PVC pipe are independent of the soil-pipe system—unlike HDPE pipes.
Besides being lightweight, PVC pipes are resistant to corrosion and non-reactive to most chemicals. But what makes PVC pipes a viable choice for a water main is the cost. Even with the cost of backfill and labour, the cost of PVC pipes is less expensive than pipes made from other materials. Fiberglass Reinforced Thermosetting Plastic (FRP)
Fiberglass pipes have grown from its original use in oil and gas to applications such as water mains. Like HDPE and PVC pipes, fiberglass pipes are resistant to corrosion. However, unlike the two other plastics pipes, FRP pipes are manufactured by a winding process instead of the extrusion method. In FRP pipes epoxy resins with continuous glass filaments are reinforced resulting in a stronger, lighter pipe with enhanced temperature handling capabilities.
COMMON ISSUES
Some common problems in water mains like leaks and bursts often result from either installation or movement in the backfill. Replacement or repair of the pipes is costly, making it vital to understand what is causing the leaks.
Leaks in tap hole
This indicates that the valve (tap) that connects a private home to the city water main is leaking, most likely due to the fittings used in the connections. In some cases, the actual tap is broken and needs to be replaced.
Leaks in footpaths
Footpaths are usually where the water main runs from the street to the house. A leak in the water main can travel in either direction along the footpath before surfacing through cracks in the cement.
These kinds of leaks are costly to repair and are most likely replaced with a new pipe.
Leaks from extreme temperatures
****Areas that experience extreme changes in temperature often experience broken water mains. The expansion and contraction of the water mains causes pipes to weaken and crack.
OUR TOP PRODUCTS
At Hynds, we manufacture a range of pipes for water main. Our top products are:
- Polyethylene Pipe (PE)
- PVC Pipe
- Seismic Resilient Ductile Iron Pipe
- GRP and FRP Pipe
- Steel Pipe
- Ductile Iron Pipe
