Reggie;
The above mentioned machines that I listed will do just fine. The worst one will be the Sanitaire, but like I said, it can be repaired quickly and inexpensively. The clean air uprights are not going do as well as the "fan-first" uprights w/sand. The original poster is concerned w/sand.
I believe that the Nilfisk is not needed in this situation. It is too expensive for a Co-op. Replacement parts/supplies are expensive also.
I just have to add, I am Reggie, not this other guy.
But my recommendation would with a clean air as well tho, not just for sand, but also for the fact that in most commercial multi-user environments that people tend to not be careful of what they suck up. A clean air system is less likely to be damaged by picking up coins, smallish toys etc., where a direct air fan can be easily broken. I would also say that clean air systems can do just as well on sand as a direct air machine. At work, I demo all kinds of vacuums to customers, most of them being clean air. When I demo a machine, I always make a mess of kapok and sand for them to vacuum up. Almost all vacuums will pick up the sand very well.
Now as for what specific vacuum I would recommend, I recommend a Windsor Sensor or Sebo G1. I have personally sold the Sebo version to several commercial places and seen them used in day care situations, they hold up very well and need no repairs other than the occasional unclog and replacement of the brushroll (as the bristles will wear out). These are all user serviceable with the Sebo and need no tools to do it. Another important thing to remember is the belt. When you are picking up large amounts of sand like dirt you really need good, constant agitation to help it get picked up, with a Sebo that uses a geared belt, so the brush is always turning at the same speed. The belt is also permanent and never needs changed. I personally think that if they give this machine a chance, they will see that it will clean very well and need less service. The added cost (a couple hundred more than a Sanitaire, close in price to the Royal) of this vacuum will easily make up for its self in fewer repairs and longer life. This is just my personal and professional opinion
