One of the best cost effective materials on the market today and of primary use in the control of water flow in some of the worlds most natural appearing water features is expandable black foam. It is relatively inexpensive and is extremely easy to use, especially when used in conjunction with the dispensing guns, which allow you to apply a controlled bead of foam as small as one eighth of an inch in diameter.
The best foam available for continuous under water use in water feature applications will consist of a high carbon content closed cell formula that will not harden, shrink or age. These attributes are very important to watch for as all expandable black foams available on the market are not created equally. It is also important to wear some sort of protective clothing and/or gloves during application, as this foam will adhere to most any surface including clothing and skin and can be very difficult to remove.
The only slight and minimal (yet acceptable) downside to the use of this foam is that it can gradually and slowly decompose “if” exposed to direct sunlight for extended periods of time. This; however; should not be an issue in water feature installations if the foam is applied using proper application techniques. When the foam is completely hidden from view; after application; this exposure cannot and will not be an issue. It is; after all; the goal of any successful water feature installation contractor to hide or disguise all manmade components and materials in order to optimize the natural appearance of their water feature designs.
How can this phenomenal material be responsible for such awesome results? Just imagine how disappointing it would be if you designed and installed a beautifully rustic section of whitewater stream, a pristine babbling brook or a lavish cascade waterfall with a pump that was sure to give dramatic results. As the pump is started up for the first time you discover that a large percentage of the anticipated water flow is not even visible as it travels under and behind the rocks and boulders you used in the construction of the stream or waterfall. This problem can be avoided by sealing and filling the unwanted voids, cracks and crevasses with expandable foam, thereby keeping the available water concentrated within the confines of the visible areas of the feature and effectively controlling the water’s course and your customer’s satisfaction.
When using this product, it is important to remember that rocks and boulders are not waterproof. Water will eventually pass through the stone material. The speed and volume with which the water passes through the rocks and boulders is primarily dependent upon the composition, density and size of the stone. By using specific application techniques you will keep this scientific fact from becoming a problem.
If you over-seal the areas surrounding a boulders perimeter, you could actually be creating a potential leak. Always remember to seal the voids around a boulder on the outside vertical edge, upstream side or backside and inside horizontal edge of each rock or boulder used in the structural foundation of your design. These three fundamental application points may not be as obvious as described here as rocks and boulders are a natural material that can take many complex and various shapes. Avoid sealing the downstream side at all cost, as water will get under the rock at some point in time. If the rock or boulder is over-sealed, this trapped water; under hydrostatic pressure; could be force out to a point where you do not want the water to go, essentially creating a “leak” that could jump the liner and potentially result in significant water loss. Adhesion of the black foam product can become more favorable when foaming larger projects by using a spray bottle of water and slightly coating the rock and boulder surfaces with moisture.
Filling the unwanted voids with the proper amount of foam is of the utmost importance as well. Normally this is approximately 40% of the total area to be filled. This amount can vary slightly depending upon temperature and humidity, which can adversely affect the curing process of the foam. I prefer to “slightly” over-fill the voids and then trim off any excess amounts later rather than under filling them and having to go back to reseal the voids again. My time is much more valuable than the slight possibility of potentially wasting a small amount of foam. If you do not adequately fill the voids with foam, you can still lose a considerable amount of water flow as water will always take the path of least resistance and if there is a way out, water will find it.
If used properly, expandable black foam can become a contractor’s best friend; if not, it can become your worst enemy. It is not intended to be nor should it be used as a structural component. It does not have the strength to hold rocks and boulders in place. But used as it is designed to be used, functional foam can result in some fantastic features when working with landscape elements primarily utilizing the movement of water as their focal point.
Increase your level of proficiency and the satisfaction level of your clientele with truly awesome results in moving water applications by adequately controlling the flow of water in your streams and waterfalls with expandable black foam.
Source: Pond & Garden Lifestyle May/June & July/August 2008