Use a strong shop vac, I think it's better then a compressor due to volume. Close the grey valve and remove the waterfall pump if you have unions. Hook up vac to blow and blow out the waterfall. Shut off main pump if in, Hook up the vac on blow to the grey valve and turn on vac and valve.
Drain and clean the fountain. Blow out the pipes to remove water and prevent the pipes from freezing and bursting. Maintain a regular schedule of clearing debris that collects in the fountain. The pump should also be cleaned according to manufacturer's directions and stored.
Cast stone is porous and absorbs water, as it freezes the water molecules expand and can cause cracks in very cold temperatures. Turn off your pump and make sure that both the tiers and the bowl is emptied.
Check for Ice Dams
If you keep your pond running during the frozen months of winter, you'll enjoy the beautiful ice sculptures that form in the stream and waterfall. Although stunning, it's possible that the ice buildup can form dams that could divert your pond water out of the pond.
Follow this advice to protect your water feature against frost, so you'll keep your fountain at its best for years to come. Never allow ice to form in your water feature. Ice forming can damage the pump and a deep freeze can even cause the structure of the water feature to crack in some cases.
As fish slow down in fall, it is time to shut off any waterfalls, fountains or bubblers and remove the pond's pump to store it for winter. The warmest water will be at the bottom of the pond where fish are hibernating, and continuing to move the water in winter would cool the pond and endanger its fish and plants.
Drain the fountain.
Unplug the pump and drain all the water from the fountain. Some fountains have a plug on the bottom for easy draining. If yours doesn't, scoop the water out with a small bucket or use a piece of tubing to siphon it out. If you have a tiered fountain, disassemble it after draining the water.
Run your pool pump continuously when temperatures are near or below freezing. You don't need to run your heater, moving water likely will not freeze. Disconnect any aerators and lines to slides. Booster pumps for pool cleaners don't need to run continuously.
Pool pipes that are located above-ground can crack if the pump is not kept running when temperatures reach below 32°. If PVC pipes freeze, the ice will expand and can crack pipes, pumps, valves, filters, and heaters.
The point of running your pool pump in the winter is to keep your water moving, which prevents it from freezing should temperatures get too low. So ideally, run your pump (and keep it running) whenever temperatures start getting close to 32 degrees Fahrenheit, the freezing point of water.
WCCO asked several kids near the falls what it would take to make a waterfall freeze. They correctly answered “cold air” and specifically, temperatures at or below 32 degrees Fahrenheit. Even one night of temperatures 32 degrees or lower can make ice form on a lake, but that's not enough time for a waterfall.
Note: Any time your fountain is running, and the temperature is below freezing, ice will form on your fountain rocks (as seen in the picture above). Ice alone should not damage your rocks.
Experts agree that outdoor fountains should be winterized to protect them from damage. ... Running a fountain in winter is not recommended when the temperature is below freezing. For fountain freeze protection, Nick's Garden Center recommends that you first unplug the pump and remove it.
Place absorbent materials such as burlap bags or old blankets in the bowls of the fountain. This allows any moisture that gets into the bowls to be absorbed instead of soaking into the bowl material and possibly damaging it when the temperature drops below freezing.
Lower the Pool Water Level
When winterizing your above ground pool, lower the water level around 4" to 6" below the skimmer. You can do this with a submersible pump or by siphoning the water out with a short garden hose.