Thursday, May 26, 2011

Effect of the Vacuum Hose on Airflow

The element of a central vacuum system that is most restrictive to airflow is the hose. Comparing the airflow at the end of different types of vacuum hoses proves this. I use a device called a Baird Airflow Meter, which measures airflow on a 1 to 10 scale. While not very useful for comparing your measurements to the manufacturer’s specs (which would be given in CFM), for example, it’s perfect for applications like this.

Starting with the Baird meter plugged directly into the wall inlet, you can see that this system pulls the indicator to 10 – lots of airflow. In fact, anything less than a “10” at the inlet usually indicates a rather underpowered system, or a problem with the power unit or the piping network.

Above is a picture of the Baird meter connected to a 30 foot, 1 1/4” ID crushproof hose. At the end of the hose, it still “feels” like quite good suction, but the Baird meter reveals that the hose has choked off 60% or more of the airflow at the inlet. In order to deliver more cleaning power to the end of the hose, you can either shorten it, or increase its interior diameter. In a residential central vacuum application, shortening the hose isn’t usually practical; the system is designed around a 30 foot hose length so anything shorter wouldn’t reach everywhere. That leaves us with using a hose with a larger interior diameter.

The picture above is the Baird meter connected to the end of a 30 foot, 1 3/8” ID crushproof hose. The reading of just under 9 tells us that this hose is delivering substantially more airflow to the cleaning tool, resulting in faster and more thorough cleaning.  While this additional cleaning power is beneficial no matter which type of attachment is being used, it shows itself most when using a turbine-driven power brush.  An air turbine brush like the Turbocat will spin much faster and groom the carpet much more thoroughly when connected to a 1 3/8" diameter hose with smooth interior surfaces.

Better still would be a 1 1/2” ID hose, but at this size hoses begin to get rather cumbersome for residential use. You might have noticed that the hoses in this example are “crushproof” type hoses, in contrast to “wire-reinforced” hoses. In testing a crushproof hose against a wire-reinforced hose, I have found the wire-reinforced hoses to be considerably worse for airflow, owing to their more corrugated interior surface.

So…what does all this mean for you? If your system could use more cleaning power, don’t pay for a service call or look into replacing your power unit just yet – look at the hose! A new hose will fit right into your existing inlets and attachments, and could provide up to 50% more cleaning power.

JCV stocks 1 3/8” lightweight durable crushproof hoses to fit nearly all kinds of systems, old or new. Call us at (630) 608-0175 or visit for more information.