External Pond Pumps

Posted by Bill Putnam on

Why External Pond Pumps?

External Pond pumps are designed for efficiency and moving volumes of water at lower RPM’s than swimming pool pumps. Typically, external pond pumps have an advantage if the pond equipment has 2 inch or 3 inch plumbing making it easy to move the water through the pipes to the filtration equipment and the cumulative head pressure or resistance is low enough for it to provide the needed flow rate. External pumps typically costs less money to run than submersible because they require less amperage in electricity. A simple comparison article shows that an external pump can save around $730 each year in money that you would have sent to the electrical company. This proves that they pay for themselves in the very first year when compared to a submersible.


Backup Pumps?

Do you have a backup pump? When checking or setting up your pond equipment after winter, pond pumps may reveal some noise from the bearings. The pump likely still performs, yet this noise is a good indication that a new pump should be ordered pretty quickly and have it ready since the pond’s biological requires the water to keep running everyday all day.

Most decent pond pumps come with a 3 year warranty and may last as long as 7 to 9 years. Having an identical pump as a backup pump is like having insurance. If you have it, likely you’re not going to need it, but if you don’t, you may be putting your pond’s fish at risk. A backup pump is not going to go to waste because it will be needed some day. When a pump fails, getting the same pump typically requires ordering on-line from a pond specialty company. Ordering takes time for it to be delivered and now your pond biological is suffering. If this is the case, it would be best to not feed the fish to reduce the amount of ammonia they produce. Do daily ammonia testing and if it is climbing, then do some water changes of 10% or more as needed to reduce the ammonia levels. (Be sure to use a charcoal filter to trap city water chlorine or add de-chlorinator when doing water changes)

Need more flow?

Wondering if you should consider a larger pump? Buying a larger pump and keeping your older pump as a backup is perfect if you've been thinking about getting more flow! One benefit right away is that your pond clarity is likely to improve. The more times the total pond volume passes through the filter, the more it is going to trap the floating debris from the water. This debris is caused from many sources. The fish may be eating algae off the walls and scraps float away. Wind is very common for much of the blame for blowing dirt and or plant pollens to the pond. If waste or muck is accumulating on the pond’s bottom, then the fish swimming close may be kicking some up.      

Self-Priming Pumps

Once people learn about the design and benefits of a self priming pump, few consider anything else. Turn it on and wait for it to create enough suction, which can take from minutes to as much as 15 minutes. First you may need to fill the pump basket if it is empty. To improve any pump in pushing water right away when turned on, consider installing a “swing” check valve in front of the pump’s inlet. A swing check valve permits water to go only towards the pump and when the pump is turn off, the flapper inside lowers and closes off any water from going backwards towards the pond thus making it fast to start the flow again when the pump is started again after any servicing or filter maintenance.

Non Self-Priming pumps

External pumps that do not have a built in pre-filter basket do not have the ability to prime and get water flowing unless they are installed below water level that would then force the water by gravity to the pump. The option most people install is a priming leaf trap that contains a basket. This then permits the pump to act close to a self priming pump because the leaf trap priming pot can be filled with water. Again, a “swing” check valve would benefit this type of setup as well in keeping water in the pipes when the pump is turned off.

Low RPM or High RPM

Energy efficient pumps have come a long way over time. Mostly the low RPM pumps are used on ponds because we need to run them 24/7 for biological filtration and to keep the electrical bill as low as possible. Some ponds may look better with more water flow or need additional water for a stream to look right. We recommend that instead of going from a low RPM pump to a high RPM pump to gain more flow, to consider running two low RPM pumps. One for the filtration system to run 24/7 and a second pump that can be set up on a timer to provide the additional flows during the hours of the day you're most likely to be out or viewing the pond. Consider connecting the second pump intake source to be from the skimmer which has a basket to trap debris which protects the pump and because this is considered to be somewhat cleaner water. You could set the timer to come on prior to your waking up and it would have enough time to clean away the ponds surface of floating leafs and junk and then shut down perhaps after dinner time and thus save money because your not running it through the night.

The high RPM pumps are sometimes needed when the total back pressure to the pump is high and only after knowing your head pressure and reviewing the pump graphs can you determine which pump would provide the flow desired. Graphs usually show head pressure in feet on the left side and GPM (gallons per minute) along the bottom edge.

Which pump for my size pond?

Ponds should have the total volume pass through the filter as often as possible. The smallest of ponds like just a few hundred gallons may pass though the filter several times an hour. The guidelines are different based on the total gallons. Smaller ponds less than 4000 gallons work great if they are turning over at least once an hour or even close. As the pond size increase, this rate is decreased. For example, a 10,000 gallon pond with a reasonable fish load and not over feeding can still have a pump that is pushing 4,000 gallons per hour and process the biological load just fine providing there is enough oxygen being created as well. This is where water features help aerate the water or use of an aeration disks on bottom drain domes. The larger the pond, the larger the surface area and this also benefits aeration as the friction of air moving over the ponds surface penetrates the water. For ponds over 10,000 gallons, it would be better if they could come close to getting the total volume to pass through in about 3 hours time. Testing the water and having quality pond filtration can be key to your success. Over 20,000 gallons, more things need to be considered and especially the fish load and or chances of ducks or other creatures that can impact the pond water quality.

The ideal pump setup

From reading the above we find ideally that the size of the pond needs to be considered for turnover rates with preference of using an external low RPM self-priming pump that has a swing check valve prior to it. The pump then pushes water to the filtration system and Ultraviolet light prior to returning to the pond’s water feature. You should have a backup pump that can be either a new pump or an older one that works fine.


Pump Brands

We prefer proven brands that have shown to be well engineered and made of quality parts. The pumps listed often times can exceed 9 years and while it is rare, can last up to 11 years. 

PerformancePro or W Lim pumps - Pumps Page Link

More clear solutions to your pond,

Bill Putnam

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