Tips for choosing 3/8" flexible water line

Almost all household appliances that use water are connected to the water supply using flexible hoses. This is usually 3/8 inch flexible hose. The connection diagram can be considered successful - the heavy body does not deform the fitting-nut connection, both on the equipment and on the pipe, loads and vibrations are damped by a flexible braided hose. But for high-quality operation of the entire system, it is important to choose the right flexible hose.

Main types of flexible liner

There are two types of connectors used to connect home plumbing. They differ both in appearance and design. Flexible liner can be made in the form of:

• a short, relatively rigid corrugated metal pipe;
• thin flexible hose with metal braid.

Both liner options differ in manufacturing technology, service life and method of ensuring the tightness of the flexible pipe.

Option with braided rubber hose

The design of the hose is a rubber hose with pressed metal nipples at the ends. Using a threaded connection, the nipple is pressed with great force against the inlet fitting of the plumbing fixture or water pipe. The tightness of the connection is ensured by gaskets, winding FUM tape or o-rings.

Braided flexible hose is available in three types:

• standard with Fittings for steel pipes: types, classification, marking and installation examples fittings on the ends of the “nut-nut” type. The nut head is available in sizes 1, 3/4, 3/8, 1/2 inches;
• eyeliner extension. It differs from the previous version in that at one end there is a rotating head-fitting with an external thread (usually 3/8 inch);
• connecting hose with a 3/8" or 3/4" movable nut (BP) on one end and a 1/2" male (HP) fixed fitting on the opposite end.

The last type of hose is a standard flexible hose for a 3/8 faucet with a straight nipple for a male threaded fitting. Used to connect sinks and bathroom faucets for hot and cold water.

Most modern mixers and faucets designed for flexible connection are designed so that inlets with 1/2-inch internal threads are located in hard-to-reach places. When installing a faucet, tightening the fittings is usually not a problem. But flexible hoses will need to be changed periodically after 1-2 years of operation. In such a situation, it becomes difficult to unscrew a stuck 1/2 fitting, even if it is a high-quality brass product.

To avoid problems with replacing the hose, use a flexible line adapter from 1/2 to ⅜. This can be a brass barrel or a tube with a nut of the appropriate size at the inlet.

In addition, one of the nipples of the 3/8-inch flexible line can be shaped like a square, and the nut, instead of a traditional hexagon wrench, has a knurled knurl.

An example is a connection hose manufactured by the German company Grohe.This allows you to tighten the nut head onto the thread by hand, without a key. This type of liner is used primarily for temporary connection of kitchen appliances. For example, a coffee machine or tabletop dishwasher.

Bellows type liner

This version of the flexible hose is a hose in the form of a steel corrugation with nuts or 3/8 fittings at the ends. Its length can reach 200 cm.

The walls are made of knurled thin strips of stainless steel. During the manufacturing process of a corrugated liner, the edges of the strip are welded, due to which the flexible metal hose becomes able to bend in the desired direction. At the same time, the product can withstand pressure up to 10 atm and temperature up to 250 ℃.

Since there is no polymer sheath inside the flexible corrugated hose, the bellows is considered to be the most durable and reliable type of liner. Actually this is not true.

Corrugations withstand static water pressure well, so a flexible line with nuts - 3/8-inch fittings can be used as a water supply section. If the pressure inside the bellows changes, then microcracks appear at the welding points of the stainless steel strip, which very poorly withstands cyclic load. Therefore, it cannot be said that a corrugated steel pipe is superior in operation to a high-quality flexible liner by 3/8 inch.

What are the technical characteristics of flexible water connection 3/8, ½ inch and other nut sizes

The design of the device for connecting water turns out to be quite complex that, having information about several basic characteristics of the liner, one could clearly judge how high-quality the product is.

The easiest way to choose a high-quality hose is to focus on the typical characteristics of a flexible hose 3/8 - ½ inch, produced by the Italian company Stout.

The quality of the product can be judged by the fact that the tightness test at the junction of 3/8 and 1/2 is carried out under pressure up to 50 atm.

Is there a difference in what kind of braid is used for a flexible liner 3/8 or another size?

The protective sheath of interwoven steel or polymer fibers performs three functions:

• protection of the sealed hose from mechanical and thermal damage during installation and operation;
• compensation of internal water pressure, otherwise the flexible polymer shell would swell and a rupture would occur at the place where the sleeve is pressed onto the nipple;
• gives additional rigidity to the hose, which is useful when installing flexible hoses in hard-to-reach places.

The braid can be made of stainless steel, coated steel or nylon. Blue or red stripes are applied over the wicker shell - this is the marking of the product for cold or hot water.

The most expensive and high-quality are flexible hoses with stainless steel braiding. This 3/8-inch hose can be installed on plumbing fixtures even next to heating equipment.

Galvanized steel braiding is often considered to be of lower quality. This is partly true. Individual fibers may lose zinc due to mutual friction, and the metal will rust.

The quality of the metal braid does not depend on the presence of a protective coating, but only on the grade of steel. The more sulfur, phosphorus and carbon in the metal, the worse the characteristics of steel fibers.Individual strands burst under load, the sharp ends of the fibers tearing apart the rubber sealing layer.

Stainless steel is considered a good choice, but not the best due to its high price. Braids made of mild low-carbon steel with a galvanized protective layer are considered a good solution.

Nylon braids are more durable in use, but they have one drawback. Polymer fibers often absorb water like a sponge, which leads to premature degradation of the polymer hose.

How to choose 3/8 inch flexible hose

If you pick up and carefully examine a flexible hose, for example, the most common 3/8-inch flexible hose in everyday life, the first impression is that it is just a rubber hose with a metal braid with a pair of nuts.

The simplicity of the product is so misleading that people often try to make flexible eyeliner on their own. Even if you manage to choose a high-quality hose for it, it will last for several months. Therefore, you should not be surprised that the first inexpensive flexible hose you bought that came to hand begins to siphon water after just six months of use. This is most likely a fake made from ordinary rubber.

Step one, pay attention to the inner shell

The flexible hose from 3/8 well-known manufacturing companies has a sealed shell made of EPDM ethylene propylene rubber. Inside it is a layer of cross-linked PEX polyethylene.The material of the sheath and gaskets placed under the nipple is always indicated in the certificate certificate glued to the hose in the area of ​​the crimp sleeve.

Some master plumbers claim that counterfeit flexible hoses, especially the most popular sizes 3/8 and 3/4, can be easily identified by smell. The fake one emits a distinct rubber smell. Often, even the smallest particles, torn off from the outer surface, spill out through the braid.

Step two, inspect the condition of the sleeves and nipples

The most reliable criterion in choosing is the build quality of the most critical parts. Therefore you need to pay attention to:

• braid condition. There should be no torn fibers or protruding strands of nylon;
• the condition of the crimp sleeves that secure the nipple to the rubber shell. The sleeves must be the same length and made of the same metal. There should be no scratches, and there should be no deformed fibers in the area where it interfaces with the braid;
• nuts or fittings should not be scratched by using a wrench. The threads on the fitting are usually plated with nickel, so if a flexible liner was used, marks will still remain.

It is advisable that the nut or fitting be made of CW617N brass or its equivalent. This is a guarantee that when tightening the connection, the material will not deform and will not give an imperceptible crack.

How to connect 3/8 inch flexible hose

First of all, the hose must be of the appropriate length. The liner after installation should not be stretched or bent with a radius of less than 50 mm. It is necessary to check the free rotation of the union nut or fitting on the mating thread. Test screwing must be done without an O-ring and only by hand.

If there are no problems, then the next step is to lay the winding FUM tape on the thread of the receiving fitting. We tighten the nut along the thread until it stops.

In cases where the liner is placed on the mixer, installation begins by screwing the fitting into the threaded receiving hole on the body crane.

After one of the ends of the connecting hose is wrapped 3/8, we lay the gasket in the same way, wind the tape, and tighten the movable nut or fitting. In this case, the hose must be held with pliers through a soft cloth. When tightening the nut, make sure that the braid is not deformed or twisted.

The last stage is a pressure leak test for half an hour. If water sweats out, turn the union nut a quarter turn with a wrench. If there is siphonage from under the fitting on the mixer, then you first need to loosen the union head on the opposite side of the hose. Only then tighten the fitting and screw the nut back into place.

The service life of the 3/8" flexible hose depends on the quality of the water. Even with professional installation of the connecting hose, the manufacturer provides a warranty of no more than two years. A good quality faucet lasts on average up to 5 years, so along with a new faucet it would be wise to buy one new connection.

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