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HOW TO


DWV SYSTEMS
THE LETTERS DWV in plumbing codes and builders' jargon stand for Drain, Waste, and Vent. The DWV is the part of a plumbing system that removes waste from a home and vents, at the roof, odors and dangerous biological gases created by waste. This venting is also necessary to maintain an equalization of air and/or water pressure throughout the DWV system so traps and toilets won't have water pulled out of them. This siphoning action would leave the house exposed to sewage gases.
DWV pipes and fittings were once assembled predominantly from metals such as cast iron, copper, and lead. Today, plastic pipe and fittings account for the majority of residential DWV systems. Because of its low cost and quick assembly, do-ityourseifers can easily work with plastic pipe.
This How-To Booklet deals specifically with the basics of working with plastic DWV materials. These materials are PVC (polyvinyl chloride) and ABS (acrylonitrile-butadiene-styrene) pipe and fittings.
CAUTION: DWV plastic pipe and fittings are accepted by national plumbing codes for certain applications. However, before making any additions/alterations to a house's DWV system, the use of plastics should be approved by the local building inspector's office. Plumbing codes, sometimes called sanitary codes, are necessary to protect the health and safety of the public and must be followed strictly.

Fig.1: Pans of a DWV system are numbered/reterencee at left and below, In most installations- you probably will be using 3-In. piping, although the material is manufactured up to 6-in diameters.

Item No. Description
1 Adapter to plastic soil pipe
2 45" Elbow
3 45' Wye (PxPxP)
4 Fitting and cleanout plug
5 Sanitary tee
6 90° Elbow
7 Closet fitting
8 Sanitary tees (2)
9 P trap with union (PxSJ)
10 Male trap adapter
11 Ptrap,'90` Elbow
12 Coupling
13 Neoprene roof flashing
14 (ABS or PVC) Pipe
15 PVC pipe (2)
16 (ASS or PVC) Solvent cement
17 (ASS or PVC) Primer
ASSEMBLY PROCEDURES
DWV piping is simple to assemble. Here are the procedures to follow:
• Develop a plan (Fig. 1). Make a sketch and go over it with a plumber or local building inspector to find out
• Which type and schedule of plastic material is sanctioned for your area. (Schedule refers to pipe characteristics.)
• How to arrive at the number of proper fittings and their respective diameters.
All materials expand and contract with heat. Some plastics do more so than others. When drilling holes through floors, ceiling, and framing members for DWV plastic pipes, allow 1/2 inch clearance. If plastic pipe binds up, it will crack and leak. Pipe installed horizontally should be supported every 4 feet, and vertical piping should be supported at a minimum of each floor height.

• Measure twice, cut once--an old carpenter's rule that is sound advice. When you are absolutely sure that you have made the right measurements, cut the pipe to size. You can purchase a handsaw designed expressly for cutting DWV plastic pipe at home centers and hardware stores. If you use a hacksaw, use a fine-toothed blade with the teeth pointing toward the front of the saw frame. Be sure friction doesn't overheat the pipe when sawing as this tends to melt the plastic and bind the saw. Use a miter box to ensure square cuts (Fig. 2).
• Deburr the cut edges (both inside and outside) of the plastic pipe after sawing, using a deburring tool made expressly for this purpose. A utility knife works if you don't gouge the pipe. Medium grit sandpaper can also be used (Fig. 3).
• Test fit the assembly of the pipe to the fitting without solvent cement. Do not use lubricants of any kind. You will not be able to fully penetrate the fitting with a dry pipe and then remove the pipe easily. But you will be able to orientate the fitting onto the pipe in the position that it needs to be when cemented. At this time, with a wax china marker, run a short line onto the fittings and the pipe. This mark will be used for aligning the pipe in the fitting when they are assembled with the cement. When you're satisfied that your system fits together, disassemble the pieces.

• PVC and ABS pipe and fittings assemble in the same way except that PVC requires the application of primer and solvent cement, while ABS needs only the solvent cement.
Apply a liberal coat of primer to the full depth of the PVC fitting socket and to a corresponding length on the end of the PVC pipe (Fig. 4).

• Following quickly, apply a liberal coating of PVC solvent cement (with the brush from its can) to the fitting socket and pipe end.
• Now join the pipe and fittings. Once the pipe is in the fitting, twist the pipe back and forth about 1/8-turn, then stop on the china marker lines. This nsures an even distribution of cement in the joint.
ith PVC materials, you must hold the pipe and fitting in this exact location for about thirty seconds before letting go. For ABS, there is only one agent (Cement) applied to pipe and fitting. There is also no need to hold the pipe and fitting in place for any length of time after joining (Fig. 5).
Once the pipe/fittings are together, you can't pull them apart. That's why it is so important for your measurements to be accurate and the reason for the dry-fitting. If you have made a mistake, the only way to correct it is to cut out a piece of the run and rtecouple it with more pipe and couplings.
If you find yourself in this situation, mark and but the pipe between mistakes. Then, using two approved "band-sea[" type couplings which act as ppenable unions, cement another pipe and fitting combination together and splice back in to the original pipe run. The band seals have stainless steel, worm-drive hose clamps which tighten them to the pipe.

PROJECT SPECIFICS
Since every DWV project has different requirements, it's impossible to give specific DWV design and detail information. For this reason, it is recommended you consult with a plumber or building inspector for proper pipe size before beginning. However, on the following pages you will find several typical projects involving DWV systems.
it is also advisable that you spend some time in a plumbing supply store, or home center plumbing department, inspecting the various DWV products Ion display.

Fig. 6: Typical DWV rough-in for new bathroom addition.
Here is a typical bathroom layout using plastic DWV pipe and fittings. Note that the soil stack's vent is connected to vents from the tub and lavatory basin. Venting allows atmospheric pressure into the entire DWV system and prevents a vacuum effect that causes slow drainage or trap seal siphoning. The pipes of the DWV and the water supply system pass through bored holes in floor joists and wall framing members. If you are changing existing plumbing, you may need to open existing walls to add new vents and drains. Drains from the bathtub and lavatory can be connected to the main drain below a toilet--downstream of the sanitary tee connecting the toilet's trap arm and the soil line. If you connect to existing plumbing (copper, steel, cast iron), buy sanctioned bandseal type couplings to join these materials to plastic.

Fig, 7: Connecting to existing DWV drain system.
Installing a now lavatory using the existing DWV orain system is a common project. Part of the ovall through which the new vent to the roof and the drain to the ewsting waste line has to opened so the proper connections ano pipe runs can be made. As mentioned in the beginning of the booklet, sketch out the proposed new system. The sketch will help you ascenorn wnether you use a WYE or a TEF at the axlshng waste floe depending upon the mentioned use of vent and drainage fittings for your lmal code.

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