It sounds like the central systems I had to deal with were installed by the home builder--not a vacuum dealer that sells central units.I also had the job of emptying the units my mom had-the BD unit was easy to do-you just lifted the large bag out of it and put in another.The Nutone was another story-you had to carefully remove the large metal dirt bin-it was heavy-don't blame mom for not wanting to deal with it.And you had to dump it carefully in the trash-or their compost pile--several gallons of dirt-you would get a faceful of it.Also a filter inside the unit had to be cleaned-took it outside and shook it out.then put the machine back together.Today I would not want a central system.I like the portable ones much better --still feel they are more eficient.I don't like the trend of the "bagless" central units-its worse than emptying a Shop Vac.I liked the BD unit that used a bag--it was so much easier and cleaner to empty-kept telling Mom--"you could do this-see-just take out the full bag and put in another"The bag was not heavy like the bin on the Nutone.It was surprizing how heavy the bin got-seems like it held several gallons of dirt.On the Nutone system-they were several airlines that went into the attic-I was one of those that got clogged.It was strange how that system was installed.And the joint came apart for cleaning-would imagine that would cause an air loss.
