Vacuum Suction Power

This experiment started when I was trying to find a use for an altimeter that I have. As a detour into self-analysis: Why do I have all of these weird things? I end up collecting and buying the oddest devices. Anyway, with the altimeter I wanted to measure the suction power of one of our vacuum cleaners (the other is an upright model that had no nozzle attachment). I used:

One altimeter, measuring from 0 to 16,000 feet, with an adjustable outer ring to calibrate to the initial altitude
One vacuum cleaner with the hose attachment
A large Ziploc bag
One barometer

I first calibrated the altimeter to read 0, so I could easily determine the change in air pressure. Then I placed it in the plastic bag, and then stuck in the nozzle, placing it against the altimeter. Zipping the bag closed as much as possible, I turned on the vacuum and then gripped the hose with my hand to further seal air, until maximum vacuum was reached. The recording on the altimeter was 4,200 feet. Since the initial value was 0 feet, the vacuum cleaner is capable of a 4,200 feet pressure difference. An excellent equation for pressure problems is p(h) = p(0) * (1-(h/145442))^5.255876. The atmospheric pressure at reading 0 feet on the altimeter (i.e. the air pressure in my house) was 30.03 inches of Hg. Thus, solving for p, the result is a pressure of 25.74 in. Hg. The difference in pressure is 4.29 inches Hg. The vacuum lowered the air pressure by 14.3%, which isn't that bad considering it is for household use.

Here are pictures of some of the equipment: