I was looking up parts sizes and found out the remote cassette vacuum generator and holding tank (Dometic VT2510) I was wanting to use was discontinued.
Most standard vacuum generators are larger than that small compact vacuum generator and holding tank were. Then on top of the vacuum generator you still need a black water holding tank. What was really nice about the VT2500 is the 3.5 gallon holding tank/vacuum tank was removable, and you could carry it to any toilet and pour it in. You didn't need to move the RV or trailer. A good vacuum flush system uses from .4 liter to 1 liter per flush so they use very little water. They also are very good at cleaning out the bowl when flushed. The drawbacks are you can't use heavy quilted toilet paper like Charmin, regular TP works fine, you need a pressurized water system, more parts and tech to break down, and cost. The loss of the VT2510 makes it real hard to fit one on a tiny travel trailer. The volume goes up from 1.6 cubic feet of basement space to around 4 cubic feet with a small holding tank.
This PDF from Dometic goes over what a vacuum flush system is, it's components, etc..
http://www.dometic.com/FileOrganizer/1-international/Operation%20&%20Installation%20Manuals/Toilets/VacuFlush.pdfBogo wrote:After using vacuum flush toilets on both boats and RVs, I'm seriously looking at spending the dough on a remote cassette type one. I'll put it's remote vacuum tank in a heated locker in the basement. To use them you do need a pressurized water system, and 12VDC at a couple amps for a few minutes per flush.