Pump Location

• Depending on where your pump is located, it may or may not be safe to place a ball valve after your filter. What is important is that you place the ball valve on the output side of the pond pump. Restricting water leaving the pump will not necessarily have a detrimental effect on the pump, but restricting intake will. Placing a ball valve on the intake side of your pump can lead to the pump running dry and eventual pump burnout.
  
  

Pond Filter Style

• If you have an external pond filter, as with a biological filter or other filter box, you can safely place the ball valve after the filter as long as it is after the pump. A filter will continue to function despite reduced flow, with no deleterious effects. If you have a substantially overpowered pump, however, you may want to opt for a T-pipe to divert some water back to the pond.
  
  

T-Pipe

• A T-pipe is a small piece of PVC that can be used to divert some of the water away from the pond filter and directly back into the pond. This is a good method to use if you have a pond pump that is pumping at too great of a rate for your waterfall or fountain. On the output side of the pond pump, a T-pipe is installed, with one line running to the filter and the other dumping directly back into the pond.
  
  

Submersible Pumps With Built-in Filters

• If you are using a submersible pump with a built-in filter box, you can safely restrict the output of the pump using a ball valve to reduce flow to waterfalls or other water features. As an alternative to a ball valve, you may want to use heater hose for the line running from the filter box to the water feature, and simply use a hose clamp on the hose to reduce the output. Tightening the clamp will reduce the flow, and loosening the clamp will increase the amount of water available to the water feature.