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What size pump for small pond waterfall?

Posted: Mon Jan 30, 2012 10:52 am
by BML
I have taken over a pond with a waterfall and when I checked the size of the pump I found that it was 690 watts which appears to me to rather expensive to run.
My wife would like a gentle trickle of water and I have no idea what size pump to go for.

Posted: Mon Jan 30, 2012 12:09 pm
by Dillbert
pumps are usually rated by their flow capacity - gallons/litres per minute.

it's quite difficult to impossible say how much volume you need for the desired effect as the size / shape / slope of the "openings" over which the water falls affect the end result. some pix would help with a guesstimate.

but, all is not lost. presuming the current pump is working - it has a hose of some sort from the pump (presumed to be situated in the "bottom" of the pond) to the high point/outlet.

put a valve of some sort at the hose outlet so you can restrict the flow - when you're satisfied with the degree of trickle, run the hose into a bucket of known volume and time how long it takes to fill up.

important: when timing the bucket fill, the height of the hose running into bucket needs to be as close as possible to the 'height' of the hose outlet in the upper pond/pool. as height increases, flow will decrease....

you can then shop for a pump that has a flow rating close to what you want and compare the motor wattage.

note that pumps are rated for x lpm at y meters height (or "head) - small inexpensive pumps may not have that degree of detail specified.....in which case it becomes trial & error . . .

Posted: Mon Jan 30, 2012 2:11 pm
by BML
Many thanks for your help. I will try that method out tomorrow and when my sons tells me how clever I am I will reply, "basic physics old mate" claiming the experiment as mine.

Posted: Mon Jan 30, 2012 5:28 pm
by Dillbert
>>when my sons tells me how clever I am

don't worry. you'll find out you're getting smarter and smarter as they get older and older (g)

the experiment is yours with my compliments. I didn't "invent" it either!
pssst: don't tell the kids. I'd hate to look dumb . . .

Posted: Sat Feb 11, 2012 1:24 am
by TheRipeTomato
I agree with what Dilbert says....you're more interested in flow-rate, not wattage. Having said that, 690W seems excessive. Pumps have come a long way in recent years....I have seen small waterfalls powered by as little as 130W!