Posted: 23/11/2013 at 22:27
KT53 Is right about the risk of washing out the joints.
If the joints have filled up with weeds, though, which is also quite common, sand is going to be lost anyway getting the weeds out by any means.
Silver sand can be replaced if lost from the joints but, admittedly, this is best done in dry weather because it needs to be swept over and into the joints.
If it is just moss, grime and slime on the surface that you need to get rid of I think this is where the 'T-Racer' comes in because it performs broad stroke scrubbing rather than a focused jet stream.(see Clarington above)