1. Water at high velocity can cause this condition.
High water velocity may be caused by an
undersized piping system, causing erosion that can cause this to take place.
The real solution is to lower the water velocity. Like a throttling valve (Globe pattern) by lowering the velocity of the water in the system you save undue wear on the internal tubing walls. You can also opt for a pressure reducing valve BUT they can be a real pain in the neck to service and globe valve keeps it simple to adjust.
The relationship is as follows:
Reduce pipe size, increase velocity; increase pipe size, reduce
velocity. Recommended velocity for hot water in a copper tube system is 4 –
5 feet per second (fps). If systems are designed to respect these velocities
the piping will last a very long time trouble free. Cold water piping could be slightly higher 2. Numerous, abrupt changes in direction in the piping system. Where
structural conditions cause numerous directional changes, long radius (1.5
Diameter) fittings should be used to minimize the interruption of laminar
3. Lack of reaming the tube ends. Burrs left on the ID of the tube can
cause interruption of laminar flow resulting in localized high water
velocity and cavitation.
4. Protrusions into the flow stream caused by excessive lumps of
solder/brazing material, improperly fabricated tees (branch protruding into
the run pipe), etc. These protrusions can also cause the
interruption of laminar flow resulting in localized high water velocity and
5. Excessive water temperature. Heating water above 140 degrees Fahrenheit
can accelerate the process of erosion/corrosion. As the temperature
increases, the velocity should be lowered. At 180 degrees Fahrenheit, the
velocity should be down around 2 – 3 feet per second (fps). ( 180 I use on commercial, industrial and institutional and heating jobs)
Bear in mind that these conditions are not peculiar to copper tube, but can
affect other materials as well. However, when erosion/corrosion does occur
in copper tube it is readily identifiable by the horseshoe shaped pitting
throughout the inside of the tubes. Identification OD these pits or grooved
corrosion-product-free areas on the inside of the tube can help you
determine that water velocity is too high and that the reduction of velocity
can correct the condition.
Sorry if I got carried away with too much technical jargon, but it is the only way to express the proper way to correct this problem and I think if you have a better picture of what’s going on it helps you with options.
You could also consider having your water tested for the pH value as copper cannot take hard water or acidic and water treatment program may have to be set up.