You may find that 1,000 gph is not enough if you plan to have a waterfall that is more than 10 inches wide. Generally for a waterfall you will want 100 - 150 gph per inch of width of the weir (the portion that the water spills over). This amount will vary depending on how smooth or rough the weir is. If you want less than a full flow then less flow is acceptable. You will also need to consider your filter and ultraviolet sterilizer (UV) to make sure that you are moving the right amount of water for these devices.
If your filter or UV has a maximum flow that is less than your required flow rate for good circulation of your pond water, then Plumbing Suppliesyou will need to divert some of the water around these devices and back into the pond. This is accomplished by adding a tee fitting in the pipe coming from the pump and before your filter and/or UV. A ball valve is added between the tee and the filter. Another ball valve is installed on the other leg of the tee. Add more pipe to this leg of the tee and extend the pipe to the waterfall or to the pond. Adjust the ball valves to get the appropriate amount of water flowing to your filter.
Calculating Head Pressure
The next thing that you want to consider is the amount of head that your system will have so that the correct pump size can be determined. The three main sources of head are:STATIC HEAD- this is the vertical distance you raise the water above the pond surface;
FRICTION HEAD- this is the resistance from pipe and fittings as the water flows through;
PRESSURE HEAD- the additional pressure required by some filters, venturis, and other devices.
Most pond applications can ignore PRESSURE HEAD. First determine the vertical distance in feet above the water surface, this is the STATIC HEAD. Next, use our Friction Loss Chart to determine your FRICTION HEAD. Add this to your PRESSURE HEAD and you can use this figure to size the pump.
We highly recommend using flexible PVC pipe that eliminates elbows and provides higher flow rates by reducing friction loss. Even though cost may be higher than rigid PVC pipe, it is much easier to install.
There is no problem in using pipe larger than required but smaller will cut your flow rate.
Submersible pump vs. External
Before you choose your pump however, there are other things to consider. Should you use a submersible or an external pump?Submersible pumps are usually less expensive and easier to install. However, some may cost more to operate and usually don't last as long as external pumps. There Sequence 1000are a lot of variables in determining the longevity of a submersible pump. How dirty the water, how often the pump is cleaned, and if it is operated continuous or intermittently will all influence the lifespan of a pump.
External pumps are generally very energy efficient and long lasting, but involve a little more plumbing and you will generally want to find a way to disguise the pump from view.
It is often good to compare the warranty of the pumps you are considering as this can give an idea of which pump will last longer. We have found that on average a pump will last 2-4 times the stated warranty period. A pump that costs twice as much as another but lasts 3 times as long will be a better value.
Calculating Operation Expenses
You can determine the operating cost of any pump by using this formula: amps x volts divided by 1000 x KWH cost x 24 hours-a-day x 30.4 days-per-month = cost per month.If the pump is rated in watts instead of amps use this formula: watts divided by 1000 x kWh x 24 hours-a-day x 30.4 days-per-month.
KWH is the kilowatt-hour cost, which you can get from an electric bill or by calling your local electric company.
Source:
http://watergarden.com/catalog/_pumps/how_to_choose.php
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