Build my own cabin - DIY projects

Installing Central Vac


Once you go central-vac you'll never go BACK!  Installing a central vac system is something almost any home owner can do themselves for minimal cost.  A central-vac system includes a large vacuum collection point, normally placed in or near your garage.  Outlets or suction points throughout your home feed  this central vacuum point.  Having the vac in your garage is handy for the cars and people will often design in kick-plates under their kitchen cabinets which are really convenient.  This website will walk you through some of the basics to designing and installing your own central vac system, provide answers to central vac frequently asked questions, and describe some of the options you have for attachments.

Planning for Central Vac

Planning is key to a successful central vac installation project.  You need to think about the best locations for vacuum inlets and also weigh the difficulty of installing in these areas.  With a little work you can reach most places.

Power Unit Location

The power unit can be located in the garage, basement, utility room or any other area that is dry and remote enough that living areas will not be affected by the sound of the electric motor. The unit must be mounted within three feet of an electrical outlet. Electrical specifications of the power unit should be checked to avoid overloading the circuit. The unit should be mounted so that it is out of the way but still accessible for emptying. If the system is to be exhausted to the outdoors the power unit should be located on an exterior wall. Venting to areas such as patios and entranceways should be avoided. ** Vacuums must breath…do not enclose. If the unit is to be located in a closet or utility room it must be vented. Louvered doors fulfill this purpose. A muffler can, of course be used to minimize noise.


Cental Vac Inlet Valve Locations

Correctly positioned inlet valves will ensure trouble-free vacuuming over the many years of service that will be received from a central vacuum system. The hose must be able to reach every corner of the house and go around furniture to get there. Drapes, closets and ceiling corners all must be reached. Central locations such as hallways, beside doors and adjacent to the bottom of staircases are ideal. Areas such as behind furniture or behind doors should be avoided. A thirty-foot string or the hose itself can be used to help plan the layout. If working with 1/4” scale blueprints a seven-inch string can be used to represent the hose. If an electrical beater brush is to be used at present or in the future the inlet valve should be located within five feet of an electrical outlet. Air-turbine driven beater brush heads do not require electricity and thus allow more flexibility when choosing inlet valve locations.


Planning Central Vac Piping System


One key step to installing a central vac system is to plan your piping.  The amount of airflow that reaches the hose is dependent on the efficiency of the layout of the tubing system. Lines are to be kept as straight as possible. Tight 90 degree fillings are to be used only at inlet valve locations and sweep 90’s used in all other applications. The picture below shows some rocks and debris trapped in the 90 degree short elbow at the inlet.  This is where you want it stopped so you can clean it out.


1. Main Trunk Line

The trunk line connects the furthest inlet valve to the power unit. Branch lines flowing into the trunk line will connect all other inlet valves. If the basement is unfinished the trunk line is best run beneath the joists in the basement ceiling. The upper floors can be accessed through closets, cold air return ducts or in partition walls. Alternatively the trunk line could run straight up to the attic and service the floors beneath by branch lines dropping through closet ceilings or partition walls. The location of the trunk line will greatly depend on the construction of the house and the location of the power unit.

2. Branch Lines

Branch lines join the remaining inlet valves to the trunk line. As with the trunk line these lines should be kept as straight as possible. Fortyfive degree fittings should be used to avoid sharp corners (90 degree fittings) when possible. Airflow direction should always be considered when installing branch lines.

Avoid Gravity Drops!

A branch line located directly below an overhead trunk line will accumulate dirt due to the effects of gravity. The result will be a pile of dirt at the base of the inlet valve every time it is opened. To avoid this situation the following techniques should be used.


Central Vac - Cutting and Gluing PVC Pipe and Fittings

Measuring: When sizing a length of tube, measurements should be taken from the base of the pipestop on the inside of the fitting. As each section of tubing is cut, it should be dry fitted before the next measurement is taken.

Cutting: The tubing should be cut as straight and square as possible. A miter box should be used if available. All rough edges must be removed with a utility knife or coarse sand paper.


 Dry Fitting: Once all the pieces are cut they should be dry fitted to check for correct fit. The markings on the fittings can be utilized to assure proper alignment.

Gluing: PVC solvent cement actually welds the fitting to the tubing. A chemical reaction permanently joins the molecules from each surface to produce an airtight seal. Before cementing, both the tubing and the fitting must be free of PVC burrs, dirt and grime. The components should be wiped with a clean cloth if necessary. Cement should be applied to the tubing only as cement applied to the fitting will be pushed ahead and create a rough bead on the inside of the fitting. This bead will reduce airflow and could cause a clog. The tubing should be inserted all the way into the fitting and twisted a quarter turn to evenly distribute the cement. All excess cement should be removed with a rag. The glue should be allowed several hours to set before the vacuum system is used.

Central Vac - Low Voltage Wiring

Another step required to install a central vac system is to route low-voltage, and sometime high-voltage, wires to each hose outlet.  One of the greatest benefits of central vacuum systems is that the power unit is turned on and off automatically. Every power unit has an on/off switch that is activated by completing a circuit at the inlet valves. Simply inserting the hose in the inlet valve turns on the power unit on many models. To facilitate this, low voltage wire must follow the tubing system. At the junction of a branch line and the trunk line the wires can be spliced together as demonstrated in the figure. There must be an uninterrupted route from each inlet valve to the power unit. The wire should be attached to the tubing with the wire ties at least every four feet.


High Voltage Wiring - Central Vac

You can use basic low voltage valve backing plates or electric valves (which have an attached J-Box for your electrician to run 110 volts to for the power brush which typically draws a couple amps.  Some central vac installations are designed to have high voltage fed in through a separate cord and outlet as shown below.  In this case, you need to think about locating you vac inlet close enough to the wall outlet for your cord to reach.

After the house has been wired and plumbed, but before the dry wall is installed is the best time to pipe in a central vacuum tubing system. Locate the inlet valve locations and nail the mounting plate to the nearest stud. Make sure the middle of the mounting plate is at the same height as the middle of adjacent electrical outlets.

central-vac-inlet            central-vac-high-voltage           central-vac-face-plate

It is best to offset the tubing using a combination of a tight 90 degree fitting and a 45 degree elbow. This will avoid problems of mounting screws puncturing the tubing as well as allowing the hole to be drilled further away from the stud where nails could ruin the hole saw. Drill a 2 1/2” hole in the center of the top or sole plate depending on the location of the trunk line. Attach low voltage wire to the tubing and push the tubing through from the floor below and cement it to the forty-five degree fitting. Leave ten inches of low voltage wire at the mounting plate for valve installation when the house is completed. Once the house is completed the inlet valves must be installed. Bare a half inch of the low voltage wire leads and wrap them in a clockwise direction around the lugs on the back of the valve. Tighten the lugs with a screwdriver. Using a twisting motion insert the valve into the hole with the hinge at the top of the valve. Do not apply glue; the gasket in the mounting plate will provide a positive seal. If the valve will not reach the mounting plate ask your dealer for an inlet valve extension. Using the screws supplied, attach the inlet valve to the mounting plate. Use the extra short screw if the longer version is going to penetrate the tubing behind. Note: Do not over tighten. If a whistling develops during operation slightly loosen the screws.

That wraps up what is required to install a central vac.  The links below will answer some additional details you may be looking for in your central vac installation.


Central Vac Installation - Existing Homes

Central Vac Pipe Options (SCH40 vs Industry Standard)

Back to the top - Central Vac Installation

Central Vac Installation - Frequently Asked Questions

Central Vac Installation Standards

Large Home Installation Tips

Central Vacuum Filtration Types