USEFUL TOOLS ...
HELPING YOU CREATE FLAWLESS WATER FEATURES
AVOIDING COMMON MISTAKES
In this section LASquare discusses the most common omissions and mistakes that give water features a mixed reputation, despite the fact that they can provide very valuable elements in "place creation" designs.
Several key issues related to water feature design are often overlooked during the conceptual design phase, by designers who may not understand the intricate patterns of flowing water, limitations of mechanical components or the complex environment of microorganisms living in water. This results in issues such as: excessive waste of water, difficulties during installation or high cost of maintenance and operation.
It is common that developers and designers (i.e. Architects, Landscape Architects, Interior Designers, Artists, etc) develop ideas that include water feature components. They usually are focusing on the feature’s shapes (pond, stream, water channel, infinity edge, etc.) and on desired, visual effects of water animation (e.g. waterfalls, jets, mist, etc.) When the conceptually developed project gets approved for development, the detailed design of mechanical components is usually completed near the end of the design phase by experts in fluid engineering. At that stage, mechanical engineers, pool consultants or skilled contractors are requested to provide a design for the mechanical components (i.e. pumps, filters, piping and all fittings) allowing to achieve the vision of the designer. However, specialists hired for designing plumbing are rarely responsible for any unforeseen consequences related to the size, location or shape of the flowing water. In some circumstances a specialty consultant may comment on the vision of the designer as being not possible or extremely difficult to build. However, in most situations a compromise is reached, resulting in construction of a feature similar to the one proposed by the initial designer. If the final effect is a success, both parties are proud of the accomplishment, but if anything goes wrong, nobody wants to take blame for unforeseen side effects. As a result, the faulty water feature eventually becomes an awkward planter or an eyesore.
At LASquare, we believe the prime reason for flawed installations is the fact that neither party takes a full responsibility for the design, nor has a complete set of skills necessary for providing a creative design while fully understanding implications of fluid engineering.
Following is a brief discussion on selected issues that are most frequently overlooked during the initial design phase:
● Storage of "Water in transit"
● Length and shape of weirs
● Splash of water
● Migration of water related to building materials
● Pool depth
● Colour of pool walls and floor
Water in Transit: This is the volume of water that creates a desired effect of water in motion (i.e. flowing stream or a waterfall) in a recirculated water system. (You may calculate this volume using LASquare Water-in-transit calculator) In a typical waterfall design, the “water in transit” is relocated by a pump from the lowest pool to the upper pool(s). While this volume of moving water flows by gravity back to its source it creates the body of waterfall. When the pump is turned off, water level in the upper pools comes down to the weir(s) elevation and the “water in transit” quite rapidly collects at the lowest point of the system. Unfortunately, the required volume of the "water in transit" is often overlooked when the size of the upper and lower pools is being established. This sometimes results in the lower pool not having the required capacity necessary for supplying or properly collecting the volume of "water in transit". For example, if the upper pool is ten times bigger than the lowest pool and the desired waterfall flow requires raising the upper pool water level by ¼-inch (6mm); the fluctuation in water level in the lowest pool will be 10 x ¼"=2.5" (10 X 6mm =60 mm). This change in water level happens rapidly and has a number of implications related to aesthetic and functional issues. If the area of the collecting pool is significantly smaller than the combined area of the upper pools, than provision of a surge tank may be necessary to supply and collect the "water in transit". This common solution may significantly complicate the mechanical design of the system and considerably raise the cost of installation and operation of the feature. That necessary fluctuation of the water level in the lowest pond or the surge tank size and location have to be anticipated during the project design phase and may significantly affect architectural or structural components.
Weirs: Difficulties of construction and required flow of “water in transit” are the two main implications directly related to length of weirs. Using LASquare Waterfall Flow Calculator you can estimate that a ± 50 ft (± 15m) long weir requires flow of ± 500 GPM (± 31.5 l/s) being pumped from the collection to the waterfall source pond, which is a considerable amount of water (imagine water moving in a full 6”Ø line at ± 5.5 ft/s or 0.15mØ line at 1.7 m/s). If this feature is designed to operate every day, the monthly cost of energy required for its operation will be significant. However, decreasing that flow will reduce the body of the waterfall potentially turning it into a trickle. One of practical solutions may be reducing the width of the waterfall or dividing the long weir into sections by introducing some gaps between a series of short weirs.
Another very significant issue is the contractor’s ability to provide the required precision while constructing the weir from specified materials (i.e. concrete or stone). Keep in mind that the entire edge of a weir has to maintain constant level, with variations not exceeding ½ of the thickness of the waterfall. For example, running a 1/8-inch (3mm) thick sheet of water (good for a gentle waterfall flowing on a 3˚ battered wall) requires variations in the weir level to be less than 1/16-inch (1.5mm). Otherwise, the water may not be distributed evenly along the edge, leaving undesired, visible patterns of dry and concentrated water flow along the weir.
Weir edge: The cross-section shape of the weir edge also plays a significant role in the water flow characteristics. A sharp edge (i.e. 90˚ angle) will (depending on velocity) allow for water to detach from the weir’s edge and freely fall down in the air. A gently rounded edge (e.g. ± 3-inch or ±75mm radius) allows water to “hug” the weir’s surface and keep flowing on a battered waterfall’s wall, thus significantly reducing the splash.
Splash: This commonly overlooked characteristics of liquids, frequently results in significant waste of water and is probably the most common, undesired side effects of many water features. Water splashing from waterfalls, jets or overflowing ponds usually flows onto adjacent paving or into planters. Wet paving becomes either a nuisance or when slippery a safety hazard. If splashed water ends in planters, soil becoming over-saturated and plant material that cannot handle excessive moisture frequently dies or looks very unattractive. There are too many variables affecting the extent of splash, making it very difficult to accurately calculate. However, LASquare recommends that the minimum distance between the source of splash (i.e water jet or an edge of a free-falling waterfall shall at a minimum double the height of the feature. Therefore, a 1 meter high free-falling waterfall or a 1 m high jet should be located at minimum 2 meters away from the pool’s edge to eliminate splashing beyond the pool. Keep in mind that in windy areas that distance may need to be increased to compensate for wind action.
Horizontal migration of water: The electrostatic charge of water droplets allows them to migrate sideways along the smooth walls and horizontal edges, resulting in effects similar to splash. A vertical saw-cut or a corner forces water to run down along its edge. Therefore, any patterns on walls (reveals in concrete or on stone facing) near the weirs will affect migration of water. From my observations a sandblasted, vertical, concrete wall with no reveals will allow water to migrate sideways from both sides of the weir at 45˚- 60˚ angle.
Pool Depth: Shallow pools (e.g. 3-inch or 75mm) create difficulties in sourcing mechanical fittings, which are shallow enough to be installed below or at water level. Also, Sun warms up water in a shallow pond faster than in a deep one, thus increasing complications related to algae and other water microorganisms. In most jurisdictions, pond depth exceeding 18 inches (0.45m) is considered hazardous and requires safety fencing. Designing pools 12”-18” (0.30-0.45m) deep appears to be the most practical.
Pool colour: The colour of the pond’s walls and floor affects visual perception of the feature and may also significantly impact the cost of its maintenance. Dark pools are perceived deeper and also mask small amounts of dust and organic debris suspended in the water and on the floor, thus may require less frequent cleaning. Swimming pool-like colour of pond invites people to wade and play with water, which may expose the owner to liabilities related to water sanitation. On the other hand, dark pools accumulate more heat from the Sun and are more susceptible to chlorine or calcium deposit stains.
There are many other, seemingly insignificant factors in pool design that may considerably affect construction cost, visual perception or maintenance issues. It is impossible to list in one article all the issues and propose appropriate solutions. If a talented but inexperienced consultant has a brilliant vision for a water feature, this vision should be developed in collaboration with an experienced pool designer (LASquare) at its earliest stage, to allow for constructive coordination of work and to navigate the outcome towards still impressive and yet practical solutions.
There are many water features in our surrounding with minor or significant flaws. There are also a lot of really good ones. LASquare strongly believes that a good, analytical observation of the existing successful and unsuccessful installations is a simple and very practical learning tool allowing for developing much more successful water features.