Michael Powers has graciously allowed us to reprint his articles on the tech site. We are working on bringing in more of Michael’s very informative articles. As for this article, pictures will be added soon
TECHIE’S CORNER Hello! Welcome to the Techie’s Corner. As I said last month, this column will cover as wide a variety of topics as possible in no particular order. If any of you readers wish to suggest a topic, I will be happy to give it a try. Bear in mind that I am notoriously weak in the areas of sound design and reinforcement. This month’s topic is RAIN. Rain on stage, real water, wet, sloppy, leaky, runny water! From a small drizzle outside a window to a real downpour. How do you get the water on the stage and more important, how do you get rid of it. When you make rain on stage there are 6 major areas of consideration. Supply, storage, delivery, recovery, control, and water quality. As you will see from reading, several of these areas overlap or become the same in different methods of creating rain on stage. First we will look at these 6 main areas and try to define and explain them, then I will follow up with a few examples of how you might create rain for a few specific situations. The scope of the column is meant to cover effects produced on live stages for a “theatre” audience, not effects for theme parks or large casinos with millions of dollars to spend. Supply: supply is just that, where do you get the water from? What is the most immediate source to the stage? Is it a sink back stage or down the hall? A storage tank like a 55 gallon barrel? If your supply is from city water in some form or another, you have the advantage of a constant pressure source. It is also cheap and easy. On the down side, if there is a leak, there is an unlimited supply of water to feed the flood. A storage tank has to be refilled, treated as necessary, and requires a pump or gravity to get the water to the rain system. On the other hand, any leak is limited by the size of the tank. Delivery: Delivery is how the water gets from the supply to the stage and how is it distributed or spread out, sprayed over the performing area or dripped behind a window. Delivery needs a force to move the water, a “pipeline” get it to where you want and a “rain head” to release the water.
Generally if an effect is to last for more than a few moments a pump or municipal pressure is necessary to provide the force. However, if you only have a single window, say two or three feet wide, a 55 gal. barrel with at least eight to ten feet of height above the window, will keep a slow, steady rain going for five to ten minutes, depending on the size and number of holes in your “rain pipe”. If the rain only needs to be outside a door as someone enters or exits, something as simple as a Hudson sprayer above the door will work. For a full stage effect a tank won’t and city water will rarely, provide the volume of water necessary. This leaves us with a recirculating system and a pump for most sustained rain effects. How big does the pump need to be? A very quick estimate can be made by figuring the total area of opening you will have in your pipes and multiplying by the height of your rain pipe or sprinkler heads above the stage. This will give you the approximate volume of water you need per second. If you figured in inches, multiply by 1728 to get the cubic feet of water. Now multiply the cubic feet of water you need by 7.481 to get the gallons. Now multiply by 3600 to get the gallons per hour (GPH) needed. The reason for finding the GPM is that most pumps are rated by gallons per hour at a specific “head”. “Head”, sometimes called “Static Head”, is the term for the number of feet the pump must lift the water to the discharge point.
For example, if your pump has to lift the water 20’ to pass over an obstruction, but the pipe/hose comes back down to 10’ at your actual rain pipe, your “head” will be only 10’. The reason for this is due to the siphoning action as the pipe hose comes back down over the obstruction. Although this effect is theoretically the same at any height, obviously there is a point where gravity and internal friction in the plumbing system put a maximum on the height you can pump the water over. The pump simply cannot get the water up to the top of the hill to start the siphoning effect. Now that you know the GPH that you need, you can go shopping for the pump(s) that will provide it. A point of importance here, the pump outlet, 1″, 1 1/2″,2″, 2 1/2″ etc. actually determines the final GPH. Your system must maintain that diameter of piping, on the average, to achieve that rating.
For example, if your pump outlet is 2″ diameter, that is 3.14 sq. inches in area. If you have a branch or “Y” in your system, each branch must have at least 1.414″ diameter, or about 1.5″, to maintain the maximum potential GPH flow. If you need more information for sophisticated systems such as water effects at theme parks, flowing rivers and waterfalls etc., that is beyond the scope of today’s column. Control: How do you make the water spray or fall where you want, and once it hits the stage, how do you make it go to your drain or catch tank? How do you keep the water from soaking the stage (or platform) floor and warping or ruining it? How you direct the spray depends on what kind of spray head or water pipe you use. The three general types of spray devices are: shower head types, including fire sprinkler system heads; rain pipes, basically pipe or hose with holes at regular intervals; modified rain pipes with some additional method of directing the water.
For examples of modified rain pipes, see illustrations 1 and 2. Fire system sprinkler heads are designed to spread the water very evenly over an area. They tend to be best for very large spaces, outdoor use and film or video applications. Spray/shower heads can be used pointed either up or down. Pointed up gives a softer, more realistic looking rain, but of course you have to have height above the piping to clear lights, teasers or other scenery. Pointed down will give you a fairly controllable, usually round or oval spray pattern. The round pattern is great in the middle of an area to be rained on but if you have to cut the rain to a sharp, straight line like a shutter cut with lights, it won’t work. Straight lines and tight control generally have to be achieved by rain pipes or modified rain pipes. Rain pipes, like shower heads can be pointed up or down. Again, pointed up gives a better look but sacrifices a bit of control. Pointed down gives better control, but has a tendency to look too regular…..like a pipe with holes drilled in it. Modified rain pipes offer the most precision control but because the control is so tight, it often doesn’t look “real”. Which is best? There is no best, only what works for you in a particular situation. It is simply a matter of what you and the director want the look to be and what constraints the set, stage, budget, time, crew etc. place on your realization of the effect. The second aspect of control is how to channel or direct the water once it hits the stage.
For something as simple as rain falling outside a window, a small trough to catch the water, tilted to a catch basin like a 5 gallon pail with a small recirculating pump in it is all you need. Rain falling outside the door or over a large portion of the stage is a different matter. The floor, whether a platform lid or the actual stage floor, must be covered with a waterproof cover, linoleum, dance flooring, sheet metal et al. Something like gloss painted masonite won’t do unless you have only one dress rehearsal and 2 or 3 performances. Even then you run a major risk of ruining the floor underneath. All seams and joints must be sealed with caulk or vinyl tape or something similar. Clear silicone caulk is a very good sealant, but you cannot paint it. Silicone caulk also comes in a few basic colors. Acrylic painter’s caulk sounds good but will not last more than a few performances. In addition it does not adhere as well as silicone to a variety of different materials. Basically you need a surface that is completely water tight everywhere except where you want it to drain. The floor must be raked toward your drains and the edges must be either raised like a curb.
The outside pipe was 4″ schedule 40 PVC. There was a slit 1/4″ wide along the entire length. The slit was at the bottom of the pipe and a 4″ strip of screen wire was inserted into the slot. The screen wire was “frayed” three or four wires along the lower edge and snipped or “pinked” to a ragged edge. The inside 3/4″ tube was drilled 1/8″ on 3″ centers, aimed straight up and connected to the supply line. The water sprayed up inside the outer tube and ran out the slit at the bottom. The slit controlled where the water fell and the screen wire broke up the “sheet” effect back into droplets. In the center of the stage I used the same basic method except I cut away ¾ of the outer pipe (illustration 2).
This created a shallow curved trough, over the pipe with the spray holes drilled in it. The spray went up and the curved trough spread the water in all directions. But no water went above the pipe system. This was important as there were lighting instruments as close as 6″ to the side and above the piping. The reason I didn’t simply one small pipe with holes drilled in the bottom is that it would look more like a lawn sprinkler with a steady stream of water, not droplets, coming from each individual hole, it looks very regular and fake. If you have at least 20′ above the stage you can do it that way as the steady stream starts breaking up into drops by then. If you noticed earlier, I used two pumps to deliver the water and two pumps to return it, why? Simple redundancy, if one pump failed, I would still have rain, maybe not as much but still rain. I also ran one delivery and one recovery pump on the same breaker. That way if a recovery pump failed a delivery pump would also shut down and maintain balance in the system. You may have noticed that the recovery pumps were half the size of the delivery pumps. Why didn’t the delivery pumps empty out the barrel faster than the recovery pumps could put the water back? The answer is GPM at a specific head. The delivery pumps had to lift the water about 15’ to clear HVAC ducts etc. in the ceiling before arriving at the rain pipes.
The recovery pumps only had to lift the water 36″ to return to the tank. The 1/4 horse pumps were rated at 2750 GPH at 3’ head and the delivery pumps were rated at 2800 GPH at 15’ head, almost equal. The way I controlled the water was to install a shallow rake on the stage under the area where the rain was to fall. I rose only 1″ in 20′ but it was enough to make the water run down stage. The stage was covered with Marley floor and all the seams were vinyl taped. Another method is to make a raised stage with a steel grate floor and a catch basin under it. In my case, the height restriction made any added elevation undesirable. As a result I had to attach the catch basin to the front edge of the stage. The catch basin was a 1′ wide trough across the front of the stage. It was 6″ deep at each end and 11″ deep at the center. The covering for the catch basin was a steel grate similar to that used on fire escapes and catwalks. The rain along the front of the stage fell directly into the catch basin and so there was very little spatter on the audience only 18″ away from a downpour. At the sides of the thrust stage there was a street curb 6″ high and 18″ wide. It channeled the water down stage to the catch basin. The rainfall on the sides was directed to fall just inside the curb so that it blocked the spatter on the patron to the sides This has been a rather basic over view of what needs to be considered when putting rain on stage. I hope I have covered your questions and given you enough information to start out on your own.
Michael Powers was 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.