Some light weight hose has a thin polyurethane lining, which is attached to the hose fabric with a hot melt adhesive.  There are two major problems with this type of construction:

A.  The thin lining which is around .010 of an inch thick conforms to the texture or corrugation of the weave, creating a rough effect.  This roughness or unevenness of the lining adds greatly to the friction loss of the water stream.

B.  The hot melt adhesive in time breaks down due to age and contraction and expansion of the fire hose as it is charged which causes the hose to stretch and expand in circumference.  When the hose is uncharged or relaxed it goes back to it’s normal length and shape.  After many cycles the adhesive breaks down and the tube releases or separates from the fabric, this is called delamination.  The tube may partially block the waterway of the hose or clog the nozzle and disrupt the flow of water.

Some hose have uneven or rough lining surfaces.  These again cause higher friction loss and lower flows.  Friction loss occurs from the outside of the stream toward the center.  As water is being forced through the hose it rubs on the rough surface of the lining, creating turbulence or friction loss.  The more pressure applied creates even greater friction loss until it destroys the stream altogether. We have proven that you can apply more pressure and actually get less water to the fire.  When this happens, the friction loss or turbulence has become so great it has reached the center of the stream.  NFPA estimates friction loss of  l-3/4” hose flowing at l80 GPM should be 43.7 1bs. per 100 ft.  Many times we have seen hose with friction loss much greater than this, due to reasons explained above.