Flexible water hoses: everything you need to know

Installation of flexible water hoses
Flexible hoses are components that have numerous applications and can involve very different fluids and materials. Although the correct mounting instructions are always provided, many failures and malfunctions derive precisely from an incorrect installation.

Flexible hoses have two main categories of applications: hoses for gas hoses and hoses for water. Based on this classification we can distinguish different types, made of different materials.

-  In rubber: they are made in such a way as to be compatible with the fluid they carry and so as to guarantee durability, without encountering corrosion. The main defect is given by the need to be checked and replaced periodically.
- In plastic: they are made of PVC and have the characteristic of being very resistant to the aggressiveness of some gases. As with rubber hoses, they must be replaced periodically.
- In stainless steel with plastic sheath: the sheath is not structural and must not contribute to the resistance of the hoses during the tests of compliance with the standards. The purpose of the sheath is to protect against abrasion and the material must be chosen so that it does not degrade or corrode the outer surface.


- In stainless steel without plastic sheath: the steel used is a steel of the AISI 316L family with low carbon content, which makes it more weldable during the construction phases.
The realization starts from the corrugated tube to which two fittings are welded at the end, one fixed and one rotating. This allows a quick assembly without particular twists.
 

For a correct assembly of flexible hoses in applications that require their use, it is necessary to follow some rules and to comply with specific regulations. As a first approximation, there are rules dictated by experience and common sense:

1. The length must always be greater than the space concerned, so as not to let the hoses work under tension and thus reduce the risks associated with damage and breakage. For this reason it is advisable to check that the tube does not twist on itself, causing anomalous and risky bends for its correct operation.

2. In the tightening phase it is necessary to use suitable tools to apply a correct force, avoiding forcing the fittings: otherwise, the risk of forming cracks increases. If O-rings are used, there is no need to apply a particular force: in fact, they do not work by compression but seal due to deformation under water pressure.

3. It is necessary to avoid in any way that the hoses, both during assembly and during operation, come into contact with other elements that could damage it instantly or over time through wear due to friction or external corrosion.
4. The bending radius indicated on the technical data sheets must always be respected. Otherwise there is a risk of causing one or more occlusions in the hoses which can lead to obstruction of the flow of the fluid that flows inside.

These indications are essential for correct installation and efficient operation of the hoses. These rules, even if completely general, can allow savings both in terms of timing (installation, maintenance, disposal, replacement), and in terms of costs (pipe costs, labor costs, intervention costs, failure costs). Furthermore, a failure can create more or less important discomforts to the health and safety of people who are in the vicinity of the installations. For this reason, attention and control are a fundamental part that must not and cannot be neglected.
 

For marketing all over the world, these flexible hoses must comply with the UNI CIG 7129 standard: it sets the criteria for the design, installation, commissioning and maintenance of domestic systems for the use of flue gas distributed by means of channels. Although this standard explicitly refers to flue gas systems, it is also adapted for flexible water hoses. In particular, it is recommended that flexible hoses are not installed with lower quality characteristics than the UNI 8863 standard. There are some rules to follow that are expressed in the regulations:
- The hose can never be extended more than twice its compressed length, otherwise the walls will be weakened. For safety reasons, we recommend never working at the limit length but only with shorter lengths.
- The assembly must be carried out avoiding in any way rubbing of the hoses: to do this, supports are used which reduce movement and the risk of damage due to wear.
- When assembling the flexible hoses do not bend the pipe near the fittings but at a distance of approximately 50 mm.
- The minimum bending radius must not fall below three times the diameter of the pipe itself. In this way it is possible to deal with the problem of aging.
These rules are reported within regulations and, therefore, have a formal value. However, there are further recommendations and additional "tricks" to allow correct and safe assembly:
- Make a visual check on the sealing surfaces, the gaskets and the threads of the fittings in order to verify that there are no defects and that all the components are clean.
- Wrap a few turns of electrical insulating tape in the middle of the tube: this unscientific method serves to reduce any vibrations of the flexible water hoses, especially those that connect the boilers.

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