i also own the same water pressure gun thingy. It will work in cleaning a sand filter if you are going to do the manual old style of cleaning the filter. Open filter, break crust, swith pump on - filter on backwash and push the nozzle of the pressure gun in amonngst the gravel while the water pumps is also helping.
Now that said the pressure gun thing delivers high pressure but only to a very small area. If you where to connect the other fitting - the one that takes car shampoo in it - you will see the small amount of water that is actually used.
In short the water presure gun thingy produces pressure but for to small area to really be affective in cleaning the sand filter. I can unfortuantly not think of another way that you could employ it to clean a sand filter.
I use the neville kit to clean my sand filter but still has to stir the gravel with a paddle to clean the filter.
Hi Colin, sorry man, live has caught up with me and now i have to work for a living....man it sucks.