Have you ever experienced water ingress into a building caused by a gutter overflow? The damage can be really substantial in addition to the negative effect on labour productivity or work in the building in question... Not to mention the image.
Whatever system of rainwater drainage used, and should be a manhole-established custom to go up to the roof twice or more times a year and clean the outlets. Their maintenance, according to Eduardo Torroja Institute for Construction Science, should be as frequent in a siphonic system as in another working by gravity.
Often we find the expression self-cleansing to refer to siphonic or depression systems. This is true and is a great advantage over slower systems. But this refers to the system of pipes and not to the outlets installed in the roof, which as we recommended, should be inspected and cleaned to prevent clogging caused by dirt that accumulates in the gutters.
The proper maintenance of outlets also results in a longer N (for flat roofs), in both cases by greatly reducing the possibility of pounding and humidity that cause progressive corrosion of desk materials.
Another important aspect of a maintenance service, perhaps less known, but that is extremely useful is the verification of manholes and buried outside networks. This inspection is not needed as often, but once a year or at most every two years, it would be appropriate and would avoid conditioning and compromising siphonic downstream discharge, either by clogging or even by the undersizing of the buried network we find on many occasions.
Finally, we sometimes find the called "fatigue" of fixations in installations after certain years. It is convenient to visually check all courses of air pipes for damage in rods, rails, etc., which may lead the installation to fail. The most critical points are usually those with maximum depression (the upper elbow joint before the downpipe) and the downpipe itself.
Thus, a proper maintenance system should include, in addition to cleaning outlets on roof, an annual inspection of the buried network and fixations of air network and downpipes at least every five years. In parallel, a rapid response service for the repair of small leaks, is increasingly appreciated for property and facility managers. The comparison between the small cost of preventive maintenance against a possible loss of water entering a building is beyond question: prevention is always better than cure.
I hope these tips are useful and we are at your disposal to study each particular case.