Recommended Pump Size For Pond?

[boogyman12]

I'm setting up a pond in the backyard that is 7ftx4ft and 3ft deep. From what I can tell, this comes out to about 630US gallons. The head of the waterfall will be about 3ft above where the pump lies. I bought the liner, 14inch waterfall spillway, skimmer (since it will be close to a tree), and pump at a local pond supply shop. However, I think they oversold me on the pump. It's rated for 3600gph. All the information I've found online says I'll probably need something closer to 2500gph.

So.. is 3600gph too much? Should I go exchange it for the smaller pump? Should I just put a valve on the 3600 pump and restrict the flow a bit? Thanks in advance for any advice!

 

[Truck]

cant you adjust flow? and why do you need a skimmer? freshwater isnt dense enough to be skimmed, unless your surface skimming.

 

[boogyman12]

cant you adjust flow? and why do you need a skimmer? freshwater isnt dense enough to be skimmed, unless your surface skimming.

I don't believe there's a flow adjustment on the pump. I'd probably have to use a ball lock valve on the return pipe to restrict flow. Sorry for not being clear; yes, I'm surface skimming.

 

[Davo86]

yes but you are needing a pump that can pump water around 5.5 feet up in the air, (from where the pump is situated just off the bottom of the pond to the top of the waterfall)
Also if the pump is going through a filter the output will be reduced further.

You can always add a t piece to the outlet if it is too powerful for the waterfall and have some of the water being pumped in at the other side of the pond for example

 

[chr15_8]

depends on the brand of pump. some pump what they say some dont. some struggle when there is head. your pump will be weaker at 3ft/1m. check the box it should say on the box/leaflet.

cant you adjust flow? and why do you need a skimmer? freshwater isnt dense enough to be skimmed, unless your surface skimming.

most koi ponds have skimmers.
1) added filtration (always a good thing)
2) keeps the surface clear.

 

[boogyman12]

I checked the pump. There is no adjustment, so I'd have to add an external valve, or do the T suggestion as above.

As for the head height, it's 3ft from where the pump sits (in bottom of the skimmer, about half the depth of the pond) to the top of the waterfall. On the pump box, it says the pump is only reduced to 3250gph at 3ft head.

From what I've been reading on other sites, it's recommended ~150gph per 1inch of waterfall. Since my waterfall width is 14inches, that's 2100gph. The next pump size down is 2500gph. I figured that the 2500gph pump - filtration loss - loss due to waterfall height would probably be just about 2100gph. Am I wrong?