There are few things more confusing than choosing the correct pump for your pond. It seems to rate right up there with quantum physics, statistics, and engineering.
This is our tried and true method for determining proper pump size. Hopefully, this helps you out.
The first factor to consider is, pond size. Yes, size absolutely matters…in a koi pond! Typically, in a pond under 2000 gallons, we are looking to turn it over 4-6 times an hour. I know that seems like a lot, but the smaller it is, the more we need to turn it.
If the pond is over 2000, but under 5000, we typically want to turn it a minimum of two times an hour. For a pond over 5000, we generally want to turn it at least once an hour, but more would be better. Cue Tim the Tool Man, and grunt!
Now, all that being said, there are several more factors to consider. The first is the speed limit maximum and minimum speed required for the filtration equipment that you choose. Whaaaaatttt? you say???? I know, it sounds weird, but there is some equipment that needs a minimum water flow (minimum speed) in order to function correctly. External filters are a prime example. They won’t work well, or get cleaned properly, without a certain amount of water moving through them. You will need to check the directions on each product you are using to determine this.
Also, all pond equipment has a maximum flow rate. Run too much water through a waterfall filter or any external unpressurized filter, and water is spilling out the sides, rather than going back in the pond where it belongs. Force too much water through a pressurized filter, and you can blow seals and connections.
The next consideration is how many points where water is leaving, and then returning to the pond. For example, if you only have a skimmer leaving the pond, you will need much less suction happening than if you have a skimmer and a bottom drain. And return jets, (I LOVE THEM!!! so I use lots) definitely contribute to the need for more flow. Jets are usually running somewhere around 500-2000 gallons per hour.
Don’t forget the waterfall! You want to make sure that you have enough flow to make a beautiful waterfall. Small falls need at 1000 gallons per hour, per linear foot, but the average pond we work on needs about 2000- 3000 gallons per hour, per linear foot.
That covers the basics of what you need to consider when choosing a pump. Now lets do an example, so you can begin to understand how all this works together.
I’m going to use Helix, because of course, we use Helix. Let’s say we have a pond that is 4000 gallons, with a single 4” bottom drain, a Helix Settlement tank, a Helix Skimmer, an external filter with a maximum speed of 5000 gallons per hour, a Helix Moving Bed Waterfall filter, and 2 return jets. The bottom drain, when being used with a Helix Settlement tank flows at 3600gph. The Helix Skimmer flows at about 4500-6500gph. The external filter flows at 5000gph. The Helix Moving Bed waterfall runs at about 4500gph. Jets flows between 500-2000gph each. So the “suction” side of the equation, (the skimmer and bottom drain) need about 8100-10,100gph. The “return” side of this equation (the waterfall and jets) needs about 5500-8500gph (The external filter is a side note in this equation, to be added in later).
This basically means, that you need a a pump between 8100 and 10,000gph. Does that make sense? I hope you are nodding your head. We would use a Helix 8200 for this job. That covers the first requirement, turn it two times an hour for over 2000 gallons, but under 5000. It gives you the minimum required for the suction side, and more than enough for the return side.
Now let’s address the external filter. We chose an 8200gph pump but the filter maximum is only 5000gph. Now are you scratching your head? Never fear, I’m still here! And this is really a very easy solution. We want the flow and turn over for the rest of the pond, so we will simply put the filter on a bypass. This allows you to divert an amount of the flow through the filter, and it will return to the rest of the water after it is filtered.
Does this mean that not all of the water goes through the filter on every turn? Yes. Is that a problem? No. It still all gets cleaned.
So, pretty short, maybe not so sweet, but hopefully this helps clear things up. If you are more confused than ever, we are happy to help design your pond equipment for you, and take out any guesswork. Send us the dimensions, including dept, and a bird’s eye view drawing of the shape of your pond. This will tell us if we need extra jets for a shape with possible dead zones. Then we will put together a pond kit that will fit your pond, and send it to you.
For more Pond tips follow us on: