Pools, Waterfalls, ...
However, let’s get the pool built. First, pools take a lot more water than most people realize. A small pool 10" deep and 4’ diameter contains 78 gallons of water. 78 gallons of water weighs 650 pounds, or, at 10" deep, 51 pounds per square foot. That is a lot of water and a lot of weight to handle. In addition the weight of scenery such as rocks or trees and the framework to hold and contain the water must be considered. Last but not least there is the live load of the actors which can add up very quickly, depending on the action or lack of it. A pair of performers weighing 120 pounds each can easily add up to one ton of impact loading if they are cavorting or dancing. If the pool bottom is directly on the main stage floor, there is rarely a problem. Most stage floors are rated at 150 pounds per square foot or higher. To exceed that loading the water, by itself, would have to be 30" deep or greater. If the pool is built into a raised level or platform, then the scenic unit has to be built to handle the weight of the water, other scenery, and the live load of all the actors that are in or around the pool at one time.
The easiest way to create a pool is to use "pond liners" that are available at garden shops, some Home Quarters, Home Depot, et al. Smaller liners, 3’ to 4’ diameter, are usually made of a very ridged plastic and molded into shape. They are commonly 10" to 14" deep and irregularly shaped. While these liners look fairly strong and self supporting, they are designed to be set in the ground with soil supporting the weight of the water on all sides. If one of these molded liners is used, you must support the bottom and the lip or edge all around. Larger liners come in the form a vinyl sheet and if you have access to a used or discarded above ground pool liner, they can work also. If you have a second hand pool liner, make sure there are no leaks in the section you intend to use. Soft liners must be supported on all sides and surfaces, just like an above ground pool. Otherwise the weight of the water will pull the liner away or possibly rip it where it is fastened along the edge.
The easiest way to support a soft liner is simply to make a 3/4" ply box (the stage floor can be the bottom). If the pool is supposed to be natural rather than man-made, build the box with as irregular a shape as possible, install the liner, and then shape the interior of the pool with real stones, astro turf etc. until the shape matches the design concept. When building a pool, it is easy to forget it once it is installed and filled. This is a big mistake because you have created a perfect place for bacteria and other things to grow. Theatre stages are also not noted for their pristine cleanliness. Dust, dirt and a myriad of other surprising things will find their way into the water. The water should be treated with a mild, non clorene pool or spa treatment to prevent any possibility of bacteria, mold or fungus growth. The reason for the non clorene treatment is twofold.
First, the clorene smell can be objectionable and is easily detected by the audience. Second, any costume that comes in contact with the water will be slowly bleached out. The water should be changed at least once a week, depending on how much contamination it gets from dust, dirt, the snow from last year’s Nutcracker......! Streams and waterfalls are two aspects of a similar problem. Both have to use a recirculating water system. Both create noise that has to be dealt with in some way. Both have to have a catch basin to collect the water for recirculating. A water fall and a stream can end in a pool, but a stream can also run off stage to a 55 gal. barrel or some similar holding and recirculating tank. Streams can be built as high tech as a fiberglass trough that bolts together in sections, or as simple as a couple of sections of corrugated culvert liner with visquene or a pool liner.
Visquene should be a last resort as it can develop leaks very easily. One rather easy method of constructing a small stream is to cut or build a series of ribs with a concave shape. Connect the ribs by laying 1/4" ply or luan sections from rib to rib. After cross bracing and securing, line the wooden trough you have built with visquene or a soft pool liner. The support structure for a stream rarely has to be built as strong as a pool, as there is usually far less water in any given section of the stream. The greatest danger to a pool or stream is if performers have to walk or wade in them. Walking or wadding present a grave danger of puncturing or abrading a hole in whatever you have used to line the waterway. First make sure that there are no foreign objects, dirt, grit, etc. between the floor and the underside of the liner. Next place a thin, firm but soft surface such as 1/4" ethafoam sheet or indoor-outdoor carpet, soft side up, between the liner and the support surface. Finally place a second layer of similar material, soft side down, where the walking or wading is to take place. This second layer must be weighted down, clamped or otherwise fastened to prevent a slip hazard. One way to help fasten down the layer in the stream is to use silicone caulk. It doesn’t really adhere to the ethafoam, vinyl or visquene but if left overnight before running water through the stream it will help to prevent slipping as performers walk on it. The amount of water running through a stream can be staggering.
A small stream 24" wide and 6" deep at the center can run several thousand gallons an hour, depending on how steep the slope is. A pump that large creates quite a bit of noise and is pumping water out at a tremendous pressure. How do you handle the noise and the stream of water that would shoot clear across your stage like a fire hose? The first trick is to reduce the amount of water needed to the absolute minimum. Build your stream as shallow as possible. Break up the flow with rocks, logs etc. Make the bottom of the stream bed a dark color with mottled, soft edged break ups, like camouflage. If performers have to wade through an area, make that a small pool, deeper if not wider. Reduce the total drop from the top of the stream to the bottom to the least amount possible. Finally, at the out put of your pump, use the principle of greatly reducing the output pressure by greatly increasing the size of the output pipe.
A simple way of doing this is to use a series of reducing couplings to increase the size of the pump output from the 1 1/4" to 3" that is the most common, to about 6"to 10". If this series of pipes is in a straight line it will have little or no effect unless it is 20’ or 30’ long. Put a 90 degree elbow or two in the system, the last one just after the final increase in size. Point the final stage straight up and turn on your pump. If the water simply bubbles up over the top, you are ready to install the piping to the stream. If you still get a slight fountain (you have one heck of a pump!) more than you want, you can add another section of pipe at a still larger diameter or you can use the "barrel method". The barrel method is simply to take your final stage pipe and aim it straight down into a 30 to 55 gallon barrel, from about 6" to 10" below the rim. When the barrel fills up you have effectively increased the final stage of your piping to the square inch area of the barrel minus the area of your pipe section.
The water will pour over the edge of the barrel in a flow instead of a jet. The easiest way to terminate your stream is to have it continue off stage, out of sight lines and pour directly into your holding/supply tank. This eliminates the need to pierce your stream bed to install plumbing and piping for the drain. If you have any choice, do not design the stream so that the stream bed needs to be pierced anywhere for any reason. There is likely to be enough trouble with unintended leaks without adding any of your own. If you must end the stream on stage, the most common method, of course is in a small pool. If possible design the pool with one 6" section of the rim lower than the rest. Then, like a gutter drain in a swimming pool, run your piping to the holding tank under the brush, grass, rocks, platforms, etc. Again, avoid having to put a hole in the stream bed liner if possible. If you must place a drain or hole in your stream bead the best method is to use two bolt on, 8", PVC pipe flanges.
Purchase some 1/16" neoprene gasket rubber and cut two discs, slightly larger than the pipe flange bases. Next cut an inside diameter hole slightly smaller than the I.D. of the pipe flanges. Finally cut out holes for the bolts. Using one of the flanges for a pattern, cut the stream bed material for the bolt and center holes. Place the flanges face to face on opposite sides of the stream bed with the gaskets in between the flanges and the stream bed lining. Cover both sides of the gaskets with silicone caulk (it will get a bit messy) making sure to surround the bolt holes and the center hole completely with no breaks. Bolt the flanges together carefully and tighten down in a star pattern. Allow this to set at least over night, 24 hours is better, before subjecting it to water. Now add your plumbing from the outside flange to the holding tank. Now for waterfalls. Water falls are really easy, they are just a stream that has a sudden drop. Everything we have discussed up to now apples to waterfalls also.
A waterfall is usually a combination of streams, pools and a waterfall. The main addition is that there will be a constant sound of water as it fall into the pool. Whether this means micing the actors, living with the sound as part of the ambient sound design, placing the water as far upstage as possible or what is up to you. One way to lessen the sound is to have the water hit a steeply slopped surface that then runs down into the pool at the bottom rather than have the water fall directly in to the pool. Making the pool shallow or having something soft in the pool for the water to fall on does not work. In addition to the noise, there is the spatter problem. All surfaces anywhere near the waterfall must be sealed within in inch of their lives or be made of a material that will quickly and easily air dry on their own without soaking the surface underneath. Anything less is to risk mildew, mold, fungus, bacteria and all the bad things that can come with them. To make a waterfall seem more impressive doesn’t take a great deal of water. Simply make the area where the water falls over the edge as flat and long as possible so that you have a very wide but thin curtain of water.
To increase the "size" of the water fall you can also hang a curtain of thin clear or silver strips behind the water(Rosco Glame) and light the water from the side or slightly from the back. If you have access to lights designed for outdoor pool use, light from directly below the waterfall shooting up the cascade can be very effective. What kind of pump should one use and how big should it be? The easiest to acquire are the submersible sump pumps available from any home improvement store, Grangers, McMaster Carr, etc. These are usually fractional horse power pumps ranging from 1/4 to 1/2 horse and from 1400 to 4200 gallons per hour and from $40 to $400. Which one you choose depends on your budget and the design perimeters of you situation. Generally it is a good idea to use the largest pump your budget allows without overkill. It is easy to restrict the flow with a ball or gate valve, it is impossible to get a pump to push more water than its rating. It is often more economical to use two smaller pumps rather than one larger one. In addition this gives you a bit of a safety margin. If one pump fails, you still have water, not as much, but some.
When using any kind of "natural" water effects, there is a great temptation to have the grass and other things run down to and in the water. Be very careful what and how you do this as there is the chance of a wicking effect pulling the water up and away. This can lead to a soaking of areas around the stream or pool and, in effect, a slow leak. The last bit of advice is to build your effect with access to as much of the stream or pool bed as possible, so that leaks may be spotted and repaired as easily as possible, without having to tear up half your set to find and fix them. As the needs and design of water effects are so varied, this discussion has intentionally been very general, with little attention to specific details. If you are actually doing a water effect and have specific questions, please feel free to contact me and I will be happy to offer what help and advice as I can. So, until next month, stay safe, don’t sweat the small stuff.....and remember....it’s all small stuff. ---
Michael Powers is the Technical Director at The Meadow Brook Theatre, a LORT B theatre in Rochester, Michigan, a Detroit suburb. Prior to The Meadow Brook Theatre, Michael has worked at such theatres as Geva in Rochester, N.Y., The Lyric Theatre in Oklahoma City, The Cherry County Playhouse in Traverse City Michigan, The Walnut St. Theatre in Philadelphia, The Pittsburgh Public Theatre in Pittsburgh and Wild Wood Park For the Performing Arts in Little Rock.