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Last Updated

09-03-2011

Water Pumps Article

A water pump is the heart of your pond. It provides constant water circulation and flow for continuous filtration. We carry a great selection of MDM Sequence & Sequel external pumps, Pondmaster, and Laguna  submersible pumps. Please click on the link below to view our selection of AIR PUMPS.

 

Choosing your pump.....
Which pump do I need?
Before you can pick the best pump for your pond, you need to determine two things: (1) what flow rate you want (2) what total dynamic head (TDH) your system requires to deliver that flow rate. Since the head affects the pump's flow rate, you must know both parameters to properly select a pump.

Flow
The exact flow rate you will need depends on many factors including the size of your pond and waterfall as well as the amount of fish, plants and sunlight. Before you can find that pump, you MUST HAVE the head required by your pond system for that flow rate!!!

Head
Head is a measure of resistance to flow. If a pump has a maximum output of 20 head feet, it means it can pump water 20' straight up in the air. If a pump is rated at 50 gallons per minute at 10 feet it means it can pump water up 10 feet and still deliver 50 GPM. As you increase the head, (above the full flow head) you will decrease the flow rate. Therefore to maximize your flow, you must minimize your head. For pond applications the three main sources of head are:

1. Static Head - This is the vertical distance you raise the water. To determine your static head, measure from the surface of the pond (vertically), to the highest point in the discharge line where the water is discharged to the atmosphere. This is usually the top of your biological filter, stream, or waterfall.

2. Friction Head - As water flows through pipe and fittings there is resistance. The higher the flow rate, and/or the smaller the pipe, the higher the resistance. Determine your overall pipe length, including equivalent length for your fittings. Consult the friction loss chart. Find where the column for your pipe diameter intersects the row for your flow rate and read your friction loss per 100' pipe. Use large enough pipe to minimize this friction loss. It is usually best to keep your friction losses to around 5 feet/100' of pipe.

3. Pressure Head - Any additional pressure required by filters, UV lights, foam fractionators, spray nozzles, etc. must be calculated. Determine the pressure drop across each device. The conversion is 1 psi = 2.31 head feet. (ie. a 5 psi drop across a filter = 11.55 feet)

To determine you TDH (as represented on pump curves and tables), add your static head, friction head and pressure head. Now that you know your flow and head, you can select a pump that provides this performance, and does so efficiently.

Priming Made Simple...
When there other choice than to put the pump above the water level, the unit must be "primed." This means that water must be introduced into the pump and the lines in order for the system to create a way for the pump to get new water into it. There are many ways this can be done however, this method is very simple and will help make the priming process less of a headache.

You will need:

  • Pump
  • Pipe
  • Check Valve (Foot valve)
  • Strainer basket (option but eases priming troubles)
  • Hose
  • Water

The first thing that you are going to do is install the foot valve on the end of the line in the water. The foot valve allows the water to only flow in one direction. There are different types, spring, flapper and mechanical. Depending on the power of the pump some of these may not work. We recommend a flapper type because they are easy to install and work with most pumps. They can be purchased at your local garden center (Lowe's, Home Depot, etc.) and are fairly inexpensive. Once the check valve and lines are in place, the pump and basket need to be added in the correct place. After the pump is in place, install the rest of the pipe. At this point the pond will be empty and all of the plumbing will be in place. It is a good idea to make sure that all of the joints are glued tightly at this point so that there are no air leaks. This will save time and extra work down the road. Now take the hose and fill the pond so that the suction point of the pipe is covered by enough water to not allow a vortex to occur (usually 8" or more). Take the hose out and put t into the discharge line of the system. This could be the point where the waterfall is or maybe it is just a point that you have left open in the discharge line. Let the water fill the line (wait until water is coming back out of the point where the hose has been inserted. Once water is coming out, start the pump. The line will be primed at this point unless there is air trapped in the line. If the pump is running correctly, fill the rest of the pond up. If it is not repeat the steps above until it begins to flow properly.

Some important things to keep in mind:

1. Inverted U's (a place where the line will go up the wall of the pond, over the wall of the pond, and then back down the side (looks like an upside down U)) are bad ideas. Air is very difficult to expel out of these points (unless a bleed valve is installed) and ValuFlo pumps will not pump if there is air in the intake line.
2. Try, try again. If the pump is spinning, it is working. When there is nothing coming out but the pump is spinning, there is a problem with the system. Generally, it is on the intake side of the pump and will be in the form of an air leak or an obstruction. With the clear pump, it will be noticeable as an air pocket right at the center of the impeller. This means there is air in the line. If that pocket is not present and the pump is spinning, there is something blocking the discharge line.