Tips of fountain design Part 2/3
We resume our section of tips about fountain design by turning to the all-important matter of water storage, feed circuits and water pumps
5.- Analyze the water storage. When the artistic design calls for one or several basins or mirrors of water in an architectural fountain, we suggest you size them so that they also store the extra volume of water required to fill the piping and keep the jets and cascades working, thereby avoiding the need to build additional water tanks to ensure all parts function properly (nozzles, undewater lighting, pumping systems, …etc) and also to prevent overflows when the fountain is out of service. Read More
- Does the arrangement of water tanks in the fountain design guarantee the minimum levels required by the water pumps when the fountain is working at full capacity? . Required water depth at the inlet to the pump suction pipes should be stated in the technical manuals supplied by the manufacturer of the pump. This will therefore prevent the inlet piping from becoming partially ‘empty’ or whirls from being generated from which air could get into the pumps and lead to some malfunctioning or even cause the pumps to stop. As an additional measure, these areas should be protected by some type of semi rigid underwater grille to prevent unauthorized access.
- For safety reasons and especially to prevent accidents with small children, open fountain basins should be relatively shallow.
- A means of automatically re-filling the water tanks to compensate the volume of water lost through evaporation should be arranged (this is of special importance in architectural fountains with a water mirror) as well as the water lost from the ‘sprinkling’ effect of the nozzles (which varies depending on the type of nozzle) and water carried away by wind.
6.- Analyze the components of the water supply and drain circuits:
- The water supply circuit to the various components or units in the architectural fountain (circuit composition, routing, distances, diameters, water inlet, etc.).
- What do the diameters of the various pipes depend on?. Water pump inlet piping should have a diameter of at least 1.5 to 2 times the diameter of the pump inlet. It is essential that an eccentric reducer is installed at the joint between the suction pipe and the pump inlet. This will prevent air building up at that point that would reduce the service diameter. It is equally important to avoid any head losses (“energy") that might lead to excess under-pressure in the water flow going into the pumps so as to prevent cavitation. In order to look at this matter in greater detail, we will publish new posts on the blog that deal explicitly with the use of water pumps in architectural water features.
- The diameter of the piping between the outlet from the water pumps and the point of delivery at the various nozzle sets is determined on the basis of economic speed. Economic speed is generally accepted to be between 1 and 1.8 m/s. .
- The diameter of the sections of piping that house the nozzles depends on the ‘set design’ required for the water jets. For example, if the intention is that the water jets all reach the same height, the diameter needs to be calculated to ensure minimal head loss in each section of piping so that the pressure at the base of each successive nozzle does not differ significantly. On the other hand, the figure below illustrates an example in which the idea is to create a clearly noticeable ‘linear’ reduction in the height of the jets. In this case, the diameter has to be calculated so that it will produce a head loss per unit of length – slope of the energy line – that ‘equals’ the slope of the line formed between the heights of the water jets.
- Drainage of an architectural fountain (composition of the water circuit, routing, distances, manifold diameter, slopes, discharge point, etc.).
7.- Analyze the water pumps.
- Select the type and requirements made of the water pumps (maximum and minimum static load, head loss, operating positions, pumping rate).
- Location where water pumps are to be fitted (submergible pump, in a dry well, size and position of the dry well, etc.).
- Installation of the pump units.
In subsequent installments of this blog, we shall deal with all matters concerning water pumps in architectural fountains.
8.- Is there any risk of water splashing? Is the location of the architectural fountain and its size on the ground compatible with the maximum height of the water jets so that no water splashing occurs? A basic rule is that the splashing effect of a water jet extends horizontally over a radius approximately equal to the height of the jet in the absence of wind.
For outdoor installations, it should be remembered that the effect of the wind enhances splashing and therefore in such cases, you should use a wind gage connected to the hydraulic circuit of the highest jet nozzles in order to turn them off while the rest of the water feature continues operating. That way, accidents involving passing traffic can be avoided, especially in those cases when a water feature is installed on a traffic circle, center medians on highways, etc...
The next post on this blog will continue with details about recommendations to take into account when designing a water feature. Among other things, we shall look at certain considerations to bear in mind such as ripples and waves, the sound of the water, and the use of lighting in architectural fountains, etc.