During my travels to the various natural Springs around Florida, I was always entranced by the various small sand boils that are to be found around the larger springs, often numerous in the rivers that flowed away, in the spring "runs" as they are called. I could just stand and stare into them for many minutes. They are so relaxing. In 1984, when I built my first Patio Paradise Fountain, I tried to include a sand boil. It looked nice, but it didn't work very well. When the pump was turned off, the sand went down and clogged the tube and pump, so I had to abandon the idea. As I have thought of fountains to include in my Display Garden in the Courtyard in Tampa, I kept coming back to the idea of a sand boil. I played around with the size of the tubing, the size of the pump, the angle of the submerged jets, the type of sand. After much trial and error, I have arrived at the solution. I am glad to share it with everyone.
First, choose a pump that is not especially powerful. I believe the pump I use for two sand boil jets is something on the order of 100 gph. One key thing is to locate the pump somewhere in the pool at a higher location than the level of the sand. The sand that works best is fine, white builders sand, as is used in plaster or stucco. Coarse sand or yellow sand just doesn't look as nice. The tubing should be large, I use half inch PVC. I plumb down to small brass barb fittings, on the order of an eighth of an inch. Here are two key tricks. First, place the jets, the barb fittings at about a 45 degree angle, down. Second, attach a small 'flapper' made of the cut out finger of a latex glove. Cut both ends of the finger of the glove, fold it on itself and attach to the brass barb fitting, say with a tie of some sort. Cover the plumbing with the sand. When turned on, the water should flow each and every time, as the flapper closes off and lets no sand clog the jet. Good luck with your own efforts. Call or email me with problems or if you get good results. 813-263-2989