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The Movies You Don’t Want to See: No Water In or No Water Out
At camp, two facilities crises are truly "show stoppers." Hands down, the first is "no water." The old saying "You only want a drink when the well runs dry" couldn't be more true anyplace than at camp. Surely, you can lead campers to water, but you can't make them drink. That is, until there's no water to be had when everyone becomes a parched camel. We'll talk about pressure systems another time, but now we're going to look at the downstream half of the two showstoppers. That's when wastewater doesn't go away. This time around, we're going to look at the piping systems that serve camp's wastewater network so that you can make better choices as you install, repair, or upgrade them.
The Land Before Time
Until the widespread use of plastic pipes, the vast majority of buried sewage collection systems were made from short lengths of one of two types of material: Orangeburg or vitrified clay (VC). Many people use the terms interchangeably, probably because VC is usually a very orange or terra-cotta color, but the name Orangeburg actually refers to the original manufacturer Orangeburg Pipe, of Orangeburg, New York. Later duplicated by a bunch of manufacturers, the material is generically known as "bituminized fiber piping." Bitumin is a hydrocarbon that you've probably seen most often as "the black stuff " in asphalt. And though the stuff on the street is somewhat different from the stuff that holds the pipe together, it's derived from the same base product — coal or oil. Many different fibers were used over the years, beginning with ground wood fibers, and later occasionally asbestos. If you saw it, you'd probably think that it reminded you of a heavy-gage toilet paper tube. It was light, easy to handle and install, and resistant to water intrusion and chemical attack. Over the years, though, its shortcomings became very plain. Back to the toilet paper tube reference, you can imagine that it might deform and squash if it was buried too deeply. Since it was transmitting unpressurized liquid, there was no perceived need for any sort of watertight joints between pipe sections. Aside from allowing liquid out, it became a source of nutrient-rich water for all kinds of vegetation. Think of camp as the perfect storm for Orangeburg sewer troubles: shallow pipes, carrying plenty of water, with lots of trees on top and around the pipelines.
It's not likely, then, that you'll find too much Orangeburg pipe at your local supply house. Instead, you may find orange-colored VC. The "vitrified" part of VC has to do with a baking process that seals the pipe, making it invulnerable to corrosive liquids and gases that are common in sewer systems. You may also hear it called "terra-cotta" because its color and fragility are much like flower pots (when they weren't plastic!). Ever wonder why septic drain field piping is called "drain tiles"? Not all that long ago, clay pipe was laid in septic fields so that the joints between the sections were open, to allow the septic liquid to drain into the stone and soil beneath. The pipe material was similar to tiles, hence the name, "drain tile." Like its Orangeburg counterpart, it, too, is installed in short lengths (usually four feet), and until relatively recently, no gaskets sealed one piece of pipe to the next. The narrow end ("spigot") was simply slid into the wide end ("bell"). Smooth, unobstructed flow relied entirely upon alignment of the hardened end surfaces of pipe matching perfectly. Unfortunately over time, the ground shifts from seasonal freeze-thaw or ground loads like vehicles, and the joints become misaligned. Where the groundwater is relatively high, even for part of the year, water often seeps into the system ("infiltration"), flooding septic systems and treatment plants. In dry season, water-seeking plant roots easily find their way into the pipe joints for a nearly unending supply of liquefied, nutrient-rich waste. Root intrusion is a huge problem for older systems served by clay pipe (see photo on facing page). And while modern sewer snakes can cut through root masses to clear blockages, the roots usually return before long. Moreover, clay is a brittle and relatively delicate material, which is very susceptible to damage from a power auger being rammed through to clear a stubborn clog. Having cleared the block, you may shortly after have a collapsed line, so carefully check the material that's withdrawn (as well as the downstream discharge) for pieces, bits, or orange color in the water. Those are tell-tale signs that the pipe is damaged and that there will be more repair work necessary soon. We'll get back to how to mend these systems a little later.
Back to the Future
Since about 1980, we've been blessed that sewer systems have really modernized. (Who'd have thought it?) Most notably is the nearly universal use of polyvinyl chloride (PVC) pipe. PVC is a tough, strong, abrasion and corrosion resistant material that's stable and doesn't deteriorate in contact with the soil or contents. It's lightweight and watertight. But many folks aren't aware that there are many different types of PVC pipe, each with its own special use. In this case, there's one specifically made for gravity sewer applications. Unlike pressure pipe for water distribution, gravity sewers operate under atmospheric pressure, with the liquid flowing in the bottom part of a circular channel. It doesn't generally need to resist an internal pressure that's working to push material out of the pipe, but instead, it needs to resist ground water getting into the pipe. SDR35 (ASTM 3034) is the specification that you want to use for gravity sewer applications. Two things make this special over the glued ("solvent welded") system, which may be more familiar to you. First, it comes in lengths up to twenty feet long, meaning that you can lay pipe five times as fast as you can with VC, and twice as fast as with a glued pipe. Fewer joints mean fewer places to allow roots into the system, and fewer places for the run of pipe to become misaligned. Second, and probably the most important, is that no pipe cleaner or glue is required to connect sections of this pipe. Sections of pipe simply "stab" together, with the spigot sliding into the bell, which has a flexible gasket already installed. Usually, the gasket contains a root inhibitor to head off any waterloving roots. Sewer line can be installed as fast as a trench can be dug, bedding placed to grade, and sections pressed together.
Let's Stick Together!
Incidentally, you may be interested to know that PVC water pipe (pressure applications) also has a similar presstogether joining system. The specification for that system is C900, but PVC waterline is also sold in pressure-rated categories. We'll save that discussion for another day, though. You are not likely to find either of these lines of pipe at your local hardware store or home center. Generally speaking, you'll have to get them through wholesale pipe suppliers. Also, each has pretty specific installation instructions that you'll want to read thoroughly before you begin. Adhering to details such as knowing how much of which kind of lubricant to use, and how far to press the pieces together could make the difference between a quick installation and a bunch of broken, leaky pipes.
Older camps may have an older system made of either VC or Orangeburg pipe, (or both) and may not be in a position to replace a whole run of pipe. So how do you work with what you have without breaking the bank? First, plan on installing a full length of new, modern pipe where you can. The longer pipe reaches make construction easy, and every joint that you remove from your system means fewer places for water to enter the system. Second, you need to think about how you're going to connect the different kinds and diameters of pipe to each other. Modern plastic manufacturers make many combinations of plastic-to-plastic couplings, but what do you do for older materials like VC or Orangeburg?
While most facilities personnel are familiar with the Fernco coupling (a rubber sleeve with hose clamps on both ends), many aren't aware that they make products to join specific materials and pipe sizes. Their product line lists literally hundreds of connectors, so the local hardware store or home center probably won't have room to stock all of the different sizes. It will be largely up to you to plan ahead, stocking what you need for when you need it. Here are some things to think about as you make those plans:
- Wherever you need to splice a piece of new pipe into a run of existing pipe, you'll need two couplings, one for each end.
- The exact coupling you use will be determined by the outside diameter of each of the pipes you're connecting, and many different types of pipe have different wall thicknesses, and so have different outside diameters. For example, 8-inch VC pipe has an outside diameter of 10.02 inches, and 8-inch SDR35 pipe has an outside diameter of 8.4 inches. Clearly, you'll need a coupling with different sizes on each end. Fernco 1002-88WC has these dimensions with an opening at one end of 10 inches (a tight fit; you'll need vegetable lubricant) and the other at 8.66 inches.
- Standard Fernco couplings bring the pipes together so that the centers of the connected pipes align. But in gravity sewers, it's connecting the bottom of the pipes that's important. Avoid obstructing the flow. You may also find yourself in a situation where you need to join two different nominal sizes of pipe, say, transitioning from a 4-inch clay to a 6-inch SDR35 pipe. Fernco also makes an "eccentric coupling," which accomplishes this exactly, accounting for the thicknesses of the different types and diameters of pipe (see photos).
You can see why it's not likely that your local plumbing supply house will have exactly what you need, since there's a breathtaking range of possibilities that they'd have to stock. The warehouse has all of the pipes you could need ready for shipment. While delivery time is usually just a couple of days, that doesn't help at all when you have a trench open and pipe exposed. By taking an inventory of what kind of pipe is in the ground, and anticipating PVC replacements, you'll have what you need right on the shelf when you need it. That would make the hardest part of a sewer repair finding the couplings when you want them. But that's another column for another day.
Back to School
There's a lot more to know about installing, repairing, and maintaining sewer systems, but not enough space here to go through it all. Here are a few tips that are worth keeping handy as you go about your dirty work. Gravity sewer pipe should run in a straight line and at a constant grade. Where you need to change grade or direction, make sure that you install a clean out to the surface right there. This helps you two ways. First, it creates a permanent string of dots at the ground surface that traces the route of your sewer. With no more guessing where that darn sewer line is, those visual reminders help prevent driving over them, or worse yet, putting a backhoe bucket through them. Second, the clean outs provide a series of access points to jet, rod, or snake a sluggish sewer line. Another thought is that you should never install a smaller sewer line downstream of a larger pipe, even with eccentric couplings. You're inviting a recurring clogged line maintenance nightmare, and your busy days don't need more surprises, especially the self-induced kind. Finally, you may be aware that there are "minimum grades" associated with each size of sewer pipe. The idea is that if your grade is at least as much as the minimum, it'll flow fast enough to clean itself out. What you may not know is that minimum grade is based on a flow rate with the pipe half full. If what's flushing upstream isn't enough to make it flow that much, the pipe won't be self-scouring, and you'll likely have stuff settling out, setting the stage for odor problems and clogs.
Having only scratched the surface, you're probably surprised to have seen how much there really is to know about sewer design. The things that your site engineer takes for granted may be big news to you. So take the time to learn some more of the ins and outs of how your system should work and plan to make it better every time you dig it up.
Rick Stryker is a professional engineer with a particular passion for helping camps with infrastructure, planning, and regulatory issues. He can always be reached at firstname.lastname@example.org or (570) 828-4004.
Published in the 2011 May/June issue of Camping Magazine.