Central Vac Pipe Options
There are essentially three options for pipe when installing a central vacuum:
Plumbing Pipe (such as schedule 40 PVC)
Vacuum Tubing designed specifically for central vacuums
Plumbing Pipe: This installation would include standard plumbing pipe (i.e. Schedule 40 PVC) that is used in the construction of homes for carrying waste water or even supply water. Generally it has an inside dimension (ID) of slightly greater than 2” (50 mm) and is available in 10 foot or 20 foot sections.
* The advantage is that this pipe is readily available in most countries and can be found at local hardware and plumbing stores. It has a thicker wall and is generally inexpensive as it is mass-produced for various applications.
* The disadvantage is that the interior of this pipe is not very critical to the manufacturing process. Generally it is assumed that it is carrying water which weight will easily push any obstructions through the pipe. The wall thickness varies greatly and the joint between the pipe and the fittings normally leaves rough transition points where stiff objects can easily lodge. Because the pipe is also fairly thick, it is normally cut with a chop-saw or hack saw and the edge of the cut normally results in a crooked and/or rough finish. This too creates a strong potential of debris getting stuck. Some retailers have offered a transition fitting for this pipe to mate with central vacuum pipe but one must always be extremely careful when transitioning from a larger pipe back down to a smaller pipe at it will increase the potential for obstructions. No known USA manufacturers of central vacuums recommend this pipe for central vacuum applications and it is not an acceptable standard for installation based upon IAPMO or ASTM F2158 standards.
Flexible Hose: This option was attempted in the early 1960’s with central vacuums and was soon abandoned as a disaster. This method employs a 2” (50mm) flexible hose in lieu of the fittings and elbows in the system. Currently this flexible hose is only used within the first few feet of VacPan locations to allow for more accurate installation capabilities. The hose currently is available in two styles; one as a vinyl material with a wire reinforcement and the other as a more rigid PVC material. Both exhibit the issues listed below.
* The advantage is that the installer can reduce his inventory of fittings and the complexity of the installation process. He would simply cut short pieces of the flexible tube any time the installation requires a bend. Some installers have even proposed running the entire system in flexible hose except where one pipe intersects another to add it into the flow. The cost savings is mainly achieved by reducing the skill required for the installer to properly install the system; having a solid knowledge of proper installation techniques.
* The disadvantage is that this flexible piping adds a tremendous amount of friction loss to the system. The air bounces as it passed the ridges of the pipe that are intended to flex when the hose is bent. Also in short radius turns, the propensity for a clog greatly increases as sharp pieces of debris could easily lodge in the corrugations of the flexible pipe. This pipe is often much thicker walled to allow for the absorption of the radius of the bends and thus this ledge is accentuated and the smaller diameter of the pipe further increases friction loss. This “ledge” is where debris and long objects can permanently lodge. Because of the unique structure of this pipe, it cannot be cut with a pipe cutter but rather only a saw, again creating additional opportunity for problems. All of this friction loss results in a major decrease in the useable AirWatts of the system. No known USA manufacturers of central vacuums recommend this pipe for central vacuum applications and it is not an acceptable standard for installation based upon IAPMO or ASTM F2158 standards.
Vacuum Tubing: This pipe is made specifically for the central vacuum industry and almost all manufacturers adhere to a strict guideline established by American Standard of Testing and Materials (ASTM) Ruling F2158. This standard was developed by pipe manufacturers, central vacuum manufacturers, installers, and consumers as a means to build consistency into the manner that central vacuums are installed. Most municipalities in the USA have adopted this as a part of the Uniform Building Code (UBC) and building inspectors in these regions have a right to reject any central vacuum installation that does not meet this standard or have this value stamped on the pipe and fittings. This pipe maintains a very concise wall thickness and rigidity to allow for maximum airflow through the system.
* The advantage is that it is specifically designed to minimize the potential for clogs in the system. Its thinner wall allows for cost savings but more importantly it exactly matches the thickness of the hub of the fittings; almost creating a bob-sled run inside the pipe wherein there are no potential gaps or crevices. The thin pipe can easily be cut with a special plastic tubing cutter to obtain a precise flat surface each and every time and professional installers also use a pipe reamer to insure that the pipe-to-fitting transitions will not present any possibility of restriction. The thinner wall also bonds more easily to the fittings without the aid of any PVC primers. All currently know back up plates in the industry are designed to fit this size pipe whereas schedule 40 pipes require a special adapter. Every central vacuum manufacturer is recommending solely the use of this type of piping over any other of the options.
* The disadvantage is that this pipe is not readily available at the local hardware store or plumbing supply house. Because of its limited production, the freight expense to obtain this pipe has become a major cost as part of the system. Countries where central vacuums are not manufactured require even greater costs to import the pipe as the pipe product is not even produced in their country. Some retailers have begun to suggest that the do-it-yourselfer should use one of the other options mainly because it is difficult for even the retailer to handle and work with storing the pipe. In the entire scope of the cost, an average installation may only incur a few dollars of additional cost for the correct pipe.
Conclusion: Vacuum Tubing is what you should use for your central vac pipe. This recommendation is supported by almost all central vac manufacturers.