Selecting a Pump for Pond and Waterfalls
When you build a pond the most exciting part is plugging in your pond pumps for the first time. After all the hard work and sweat all eyes will be fixed on the water and waiting for it to begin flowing into the pond. If you have a bio filter the water will fill that up, then hit the first spillway.. and drop down either into your pond, or into other drops in the stream. This is where you will realize whether or not you sized the pump correctly. It will either have a beautiful look and sound to it, or it will look like a leaky faucet because you got the wrong size and it is not capable of pushing enough water required.
How to Choose the Best Pond Pump for the Job
There are 3 main types of pumps for ponds your can choose from;
- Direct Drive Pond Pump - These pumps are made to be fully submersed and are designed with a sealed internal electical motor. They are generally more powerful and can push more water compared to the other pumps. The disadvantage is that they use up more electricity and you will have a higher monthly electrical bill.
- Mag Drive Pond Pump - Energy efficient and submersible are the main advatages here. They are designed with a magnet attached to a shaft in the motor. There is another magnet that is connected to the pumps impeller in a seperate chamber and it spins as the other magnet spins. Another benefit is since it is magnetic driven there is no oil in the chamber that could leak into the water feature. The disadvantage is that you are going to pay more up front for these pumps.
- External Pond Pump - Large flow can be created with external pond pumps. But, they have to be installed outside of the pond water and above the water line with most. But, the one advantage to that is easy access if you need to do pump maintence.
Here is a video from Atlantic Water Gardens. You can view a couple of different types in it.
Figure Out Flow Rate
The first step after you have decided on what type of pump for pond you are going to use is establish your desired flow rate in your waterfall/s and stream.
As a rule of thumb we use 1,500 GPH of water flow for each foot of spillway/weir. With this amount of water flowing over the spillway you should have a good looking flow that covers the entire width of the waterfall.
Example: You have a waterfall spillway that is 4' wide. You should select a pump that will give you 6,000 GPH at that point after all loss is taken into account.
You can also play around with the width of the stream. If you want a slow moving section..just like in nature just widen it out. Rapids.. narrow it down. The more random you can make things usually the more natural it will look. A straight line stream all the same width makes for a boring backyard water feature.
What Kind of Losses Are There?
As mentioned that 6,000 GPH pump will not give you that amount once you start adding in height, pipe friction, etc. The longer and higher you push the water the less flow it will produce until you finally get to a point where the pump will simply shut off as its too demanding on it.
Static Head - Static head is basically the overall height that pond pump is going to have to push. To figure this out measure the difference between where the pump sits to the height of the waterfall spillway.
Friction Head - This is mostly caused by friction loss from plumbing. It will change depending on the diameter of the pipe, material of pipe, and how many and what type of fittings are used. Sweeping bends cause less friction than a tight 90 degree bend would. Flexible PVC also has less friction than a kink free pipe would because flexible pvc pipe has a smooth inner bore.
Total Dynamic Head - When you add up static head, and friction head with the flow rate of a chosen pump for pond you will get your total dynamic head of TDH. You can use TDH calculators to figure out TDH instead of doing it long hand.
The pump manufacturer should have this info for you in a graph to easily allow you to see what kind of flow the pump produces at certain head heights.
This is where your dream water feature can get crushed if you are on a budget. If you want a huge waterfall gushing down a large hill with elevation your electrical bill can get really high. So keep in mind when designing your koi pond or water garden that the larger the design the more electricity it will require.
What you may want to do is use mulitple pumps on larger ponds. The benefit to this is if you only had one pump and it failed you have no water flow at all. But, if you had two pumps and one failed the other pump would keep the feature moving until you can get a replacement in there. Having a replacement pump on hand is also a really good idea if you have koi fish in your pond. As they require a constant flow of oxygen to survive.
Important - Use a qualified electrician that knows your local codes and regulations. He will use the proper material to allow your pump to run without voltage fluctuations that could cause premature pump failure.
Have the electrician place the outdoor rated GFCI outlet with cover and lighting transformer near your pond skimmer, or where the pump will be located. That way the pump can easily be plugged directly into it. You can disguise the outlet with plants, fake boulders, wood, real stone, etc. GFCI outlets will provide protection from short circuits, overloads, and also ground faults. If it detects any of these symptoms it will quickly shut off the power and could help save someone from getting zapped! Sometimes you may need to reset the breaker button on the outlet, but if it keeps tripping you need to have a pro look at it and figure out what is going on. They are really sensitive and will trip from as little as .005 amp fluctuations.
The majoirty of pond pumps will use 115v as a standard. But, some of the bigger pumps do have the option of 230v. The electrician will check this along with how many amps it uses.
Troubleshooting Pumps For Ponds
Even if you do everything correctly sooner or later your pond pump is going to fail. Hopefully after years of trouble free use, but sometimes ever new pumps can have problems.
- Pump Getting Water - Sometimes if your water level gets low your pond skimmer will not be taking in enough water and the pump is pushing it out faster than it is coming in. At that point it will start to suck in water and cause damage to pump. You will often hear the pump making different sounds when this is happening such a gurgling or hum.
- Make sure that there is nothing blocking water flow to the pump. Sometimes debris can build up and clog everything up.
- Vapor Lock - Air may get trapped in the volute of the pump when it starts taking in air and not water. When a pump for pond gets vapor locked you will often hear a hum sound and the impeller will be spinning, but it will not be pushing water. A simple fix for this is to simply tilt the pump so the air can escape from the intake. You can try without removing from the plumbing, but your may need to disconnect any check valves, etc.
- Electrical system - Measure your voltage at the outlet to make sure you have a constant voltage. When you use a extension cord it can cause problems because they are not built for a premanent installation.
- Has the GFCI tripped? If you had a thunderstorm or something a GFCI can trip. So simply push the breaker buttonto reset. But, if it keeps tripping call an electrician.
- Check the pump to see if the impeller may be clogged. Frogs, debris, leaves, etc can get sucked into the pond and clog it up. So inspect to make sure this did not happen.
- Does the impeller spin - Sometimes impellers can freeze up and a nudge with a screwdriver will un-stick them.
If you are still having issues you may have a bad pump on your hands. Check to see if it is still under warranty and go from there to have the manufacturer inspect the pump for failure. Most pond pumps fail for two common reasons;
- Seals - Once the seals go moisture can seep into the pump and trip the breaker. This is why we always reccomend you store your pump in a bucket of water if you are pulling it out for winter. If allowed to dry out the seals have a high chance of going bad.
- Bearings - If the impeller fails to spin you can usually guess its the bearings. This is where a cheap pond pump versus a quality pond pump comes into play. The better pump will have better bearings that will last for a long time with worry free enjoyment.
If its past your warranty period you may have to bite the bullet and purchase a new pump for pond.