There are two common types pf pond pumps.  They are the submerged and external pond pumps.

Submerged Pond Pumps

                Submerged pond pumps are the most common type of pond pump.  Just as the name suggests, the pump is located in the water and fully submerged.  The water is typically discharged directly to a fountain, water fall or filter.  It is important to keep the pond pump fully submerged to prevent overheating and the aspiration of air.  These pumps discharge heat directly into the water so you want to have a properly sized pump to prevent adversely affecting the overall temp in the pond.  Also, if the water level is too low you will begin sucking air into the pump and reducing its overall efficiency while adding extra wear to the impellor.  As with any equipment utilized around or in water make sure it is plugged into a properly functioning GFCI outlet.

Types of External Pumps

External pond pumps are generally measured in horse power and are the larger of the pond pumps.  The install is usually more in depth since it requires more elaborate plumbing and power requirements.  The sizing based upon the pump curve and the max Hp you can install is based upon what electrical source you have available.  External pond pumps are typically 110v or 220v and you may have to consider installing a dedicated power line and breaker to the pump.  For this you would need to size your pump then consult and electrical professional before you proceed forward.  There is no need to buy a pump that your cant install.

Two types of external pond pumps to understand are as follows.

  • External above ground pool/pond pumps
  • External in ground pool/pond pumps

The difference is very important.  One pump will be net positive on the suction side where as the other requires pressure on the suction side to work.  So what does this mean?  For the “Above Ground” variation the actual pond level is ABOVE the inlet of the pump.  This puts head pressure on the inlet of the pump and allows it to prime and function properly.  The “In Ground” pump does not need extra head pressure on the inlet side to prime and pump.  There is a limit to how high the pump can pull up or how far down the water level can be to properly prime and this will be listed in the specs of the pump.

Pond Pump Curves

Most pond pumps will include a pump curve.  This will allow you to properly size your pond pump.

The two parts of the graph include the TDH or “Head” and the flow rate.

TDH – “Total Dynamic Head” or just “Head” is basically how much liquid flow the pump will deliver at a given straight up height.  For example, in the graph below the pump will move just over 1500 gallon per hour at 0 head(ft) or at the discharge point of the pump.  Remember the “head” value is for a straight run.  So in the curve below, if the straight up run was 16 ft, the fluid would make it to the top of the pipe and just sit there, no flow would discharge.

To calculate the flow across a system (from pump to discharge) you have to take into account friction loss to elbows, in-line filters, etc..  The “head” in ft can be converted to PSI by multiplying “head” in ft by 2.31.  This is useful when your calculating pressure drop across your entire system.  Delta P or the change in pressure is a common measurement across a system from pump to discharge.

 

Sample Pump Curve
Sample Pump Curve