Plumbing is one of the most important and integrated components of housing. Plumbing provides water for drinking, bathing, washing and cleaning- functions of human life very important from the point of view of hygiene, making it absolutely essential that the plumbing system be carefully planned. With the advent of new advanced materials for plumbing, the choice for selection has widened. With ever increasing awareness of the importance of plumbing, characteristics of the piping material used for modern plumbing system have become very important. Composite pipes are designed to satisfy all the requirements of modern plumbing system.

The characteristics of the piping system are to be reviewed from the end users' as well as the builders' and plumbing agencies' point of view. Some important characteristics are discussed here for the adaptability with PE-Al composite piping system.

Thermal strength:
The piping material should have adequate strength for wide range of operating temperatures when used for plumbing. Considering the climatic conditions of cold regions, the operating temperature for plumbing systems starts from -40 degrees Centigrade. Considering hot water piping application in plumbing, the design temperature is 65 degrees Centigrade. Adequate safety against failure at a malfunction temperature of 95 degrees Centigrade is essential.
PE-Al pipe is made of Aluminium and polyethylene composite that combines the best features of both materials to form a pipe that is light, strong and does not support corrosion. By combining the two materials along with adhesive layers, PE-Al pipe provides adequate thermal strength for a wide range of operating temperature of -40 to 80 degrees centigrade with design life span in excess of 50 years. Short-term excursions in the hot water temperature up to 95 degrees centigrade will not affect the overall performance.

Effective insulating properties :
It is essential for the piping material to have effective insulating properties. Materials with high thermal conductivity are required to be insulated to minimize the effect of discoloration in case of concealed piping. In case of external hot water piping the heat loss from the pipe is one of the major area of attention. PE-Al pipes have Thermal Conductivity of 0.43 Watt/[m Ok.]. Due to this low thermal conductivity, the rate of heat removal from the hot water pipes is very low. Thus, no insulation is required to be provided in case of concealed piping. For external piping, the insulation requirement is approx. 50% that of conventional metal pipes.

Thermal expansion and contraction:
High coefficient of thermal expansion and contraction results in stresses, which can lead to cracks in support structure as well as effect of abrasion. Hence it is always desirable to have piping material with low thermal expansion coefficient. PE-Al pipes have a low coefficient of linear expansion. This eliminates the need of installation "offsets" and the concern about abrading pipe due to constant movement as a result of temperature changes. Straight runs are always attainable with PE-Al pipes. Coefficient of Thermal Expansion for PE-Al Pipe is 25x10-6 / O K. Low expansion coefficient is due to tie layer, which eliminates the differential expansion of plastic and metal.

Non-corrosive, Clean, Safe and hygienic:
In case of plumbing systems, the piping material being non-corrosive as well as not to have any effect on water quality is of prime importance. PE-Al pipes have inner and outer layers consisting of polyethylene (PE), having, perhaps, the best chemical and corrosion resistance of any plastic used in the manufacture of plumbing pipes. The polyolefin family of plastics - PE included - is renowned for it's toughness, long service life and resistance to deterioration in the most extreme environments. PE inner and outer layer of PE-Al pipe is unaffected by corrosive soil or aggressive water.

Clean, non-corroding plastic interior of PE-Al pipe is resistant to deterioration in aggressive water conditions. There will never be any problems about odour , colour or taste arising because of the plumbing pipes. Because of built-in permeation barrier in the form of Aluminium layer, buried water pipes will not be permeated by ground source contaminants. PE-Al pipe is hygienic, non-toxic, rust free and eliminates growth of microorganisms. This avoids contamination to water. PE-Al pipe has passed all tests of pipe for potable water in accordance with British Standard BS 6920 by the British Water Quality Center .

Quiet with no noise:
Demand for today's plumbing system is for quieter, more efficient system. Noise often associated with water hammer is generally not acceptable. PE-Al pipe offers the strength of metal pipes without all the noise. Unique composite construction of PE-Al pipe reduces water hammer pressure and the plastic layers reduce the noise. With PE-Al plumbing systems there will not be any shaking or rattling.

Consistent performance through out life span:
The piping material should not support any scale buildup. It leads to reduction in flow over a period of time. The inner surface should be smooth to avoid the scale buildup as well as give higher flow rates with minimum friction resistance to flow.
Smooth inner PE wall of PE-Al pipe permanently resists scaling and mineral build-up, keeping water flow constant year after year. There will not be a reduction in flow area with PE-Al pipes, leading to constant water pressure throughout the house, through the years.

Less physical exertion:
The piping that requires higher level of physical exertion is prone to failures due to the mistakes, which creep in through human error.
Convenient, lightweight coils of PE-Al pipe facilitate to install a professional plumbing system quickly and efficiently. Installation crews are less fatigued and larger coils mean less wastage.

Quick to join with minimum joints and fewer fittings:
In any piping system, it is always desired to have minimum number of joints to minimise the failure incidences. With lesser number of joints, the installation of piping can be completed faster. Easy to handle piping systems facilitate early project completion and leads to reduction in total project cost.
The unique feature of PE-Al pipe is it's malleability. PE-Al permanently holds whatever shape it is formed into and does not need additional clips or brackets to retain the shape of bends or curves. PE-Al is easily formed into curves, sets by hand and only requires bending springs when forming tight bends down to radius equivalent to 5 times the diameter of pipe. With this unique property, the bend and elbows are totally eliminated from the piping. This leads to lesser number of joints and fittings.
In addition to this, When the system calls for a fitting, pipe is required to be simply cut, beveled, connected with the end of the fitting and the nut is tightened for secure, long-term connection. It's fast and simple. The type of fittings used with PE-Al composite pipe are explained here.

Composite Fitting Internal Sealing
	The sealing is on ID of pipe. When the nut is tightened, the split ring compresses the pipe. This leads to compression of 'O' rings leading to positive sealing. The split ring holds the joint in position.  Size range : 1216 to 3240 PE-Al Applications: Hot and cold water plumbing, compressed air.

Brass Fitting Internal Sealing
	Although the design of split ring and nut is different, the concept is same as that of internal sealing composite fitting. The sealing is on ID of pipe. When the nut is tightened, the split ring compresses the pipe. This leads to compression of 'O' rings leading to positive sealing. The split ring holds the joint in position. Size range : 1216 to 3240 PE-Al Applications: Hot and cold water plumbing, compressed air, natural gas, LPG
Composite Crimp Fitting Internal Sealing
	The sealing is with the 'O' rings, seated in grooves which are surrounded by machined barbs. When crimp ring is pressed onto pipe by using PE-Al crimping tools, the O ring gets compressed. At the same time, the crimp ring forces the tubing on the barbs leading to permanent joint which is held together by crimped ring .All these design aspects contribute to water tight permanent joints. Size range : 1216 to 2025 PE-Al Applications: Hot and cold water plumbing