Elevating a Gas Hot Water Heater
You don't necessarily need to elevate it to protect it from the dirt.  They make a water heater drain pain http://www.homedepot.com/p/24-in-Plastic-Water-Heater-Drain-Pan-15021/204834496 for this purpose.  (I have no affiliation with home depot, they just have a conveniently searchable site).  They're 1) cheap 2) solve your problem and 3) have a hose fitting to attach a line to your sump pit or floor drain.