It will be a lot, as you face several issues. First issue: This is a very large pond you are looking at, in the range of 11,000 gallons (using the calculations you provided). It sounds as if someone had a very serious koi pond at one time. Although you state you are leaning toward not keeping fish, I would want bottom drains installed in a pond of this size, or you will end up with a mucky mess in a couple of years. If this was a properly designed koi pond, some of that plumbing may still be in place. So the first consideration is that you will need a pump that will filter something on the order of 5,500 to 10,000 gallons per hour, 24 hours a day. A Dolphin Ampmaster ES5500 external pump would perform this function relatively inexpensively, at about 286 watts per hour. I've seen that pump listed for around $400. The second issue is that a pump like the Dolphin will not push water to the heights you are considering for your waterfall. You need a pump that will push 40 feet or greater "well head" height -- the vertical distance that a pump will raise a column of water. For this, you will need a powerful unit like a Sequence Primer which draws around 1500 watts per hour. That is about the same as a large window air conditioner. Where I live in Virginia, the math works out like this: 1500 watts = 1.5 kWh x 7 cents = $1.05 per hour. (I think the national average cost is more like 10 cents per kWh.) Therefore, since you must run filtration 24 hours a day, you are probably looking at two pump systems. The filtration could be accomplished with a low-cost unit like the Dolphin. Your waterfall would be fed by a second very powerful pump that you'd run only for those hours each day when you want to operate the waterfall. You could reduce your cost somewhat by lowering the height of the waterfall. If you are serious about this project, I would recommend first reading up on koi pond design and construction. (There are several websites which specialize in this subject.) Also, some of the experts around here will hopefully chime in. This is not a "garden-variety" pond project that you are considering!

Joe, Thank you,We will go and take a look at the performance pros.. The only thing we have concerns about with the externals is where to put them? With the water garden built off the side of the house, the top falls(not used often) water pipe is actually under the rock up to the roof (15 foot straight up lift).I believe we would have to go low ,down by what is a holding tank similar to a pond less feature. Can you tell me how large of area I would need to have to house the pump? We may be able to find a way to create a small space,, but with all the large stone we would have to bring in the skidster to move stone which right now is not an easy task. We do have a space in the block walls that hold the hot tub as well, but not sure how that would work for plumbing.Or if the pump running all the time would be to noticeable to those using the hot tub.. I guess I am off to research more. Thank you for your input we appreciate it. Mary

First thing first. Larger filter = less operating pressure on the same flow rate. Second thing. In the absence of a visible leak in your equipment pad which will cause the filter to drain back, you have a classic gravity feed. This can happen simply by design of the system. More often when the equipment pad is slightly elevated above the pool line. On the other post, yes, you don't program gpm into the filter mode of an IntelliFlo directly. It is a calculated number based of the cycle, volume and hours. You'll need to install a full flow check valve in the line between the pump and filter. Use a Pentair of Jandy model, 2.5 x 2.0 CPVC. Now the issue. You put flex line there and that is going to cause problems. The weight of that valve may overwhelm the pipe. This line should be rigid pvc and you will certainly develop a leak later if it is glued into the backwash valve. On the other post. Yes, you don't program gpm on an IntelliFlo filter mode. It is a calculated number based on cycle, volume and hours. Those numbers are not known until you have your desired gpm and the final operating flow is + - a gpm or 2. The FEATURES do account for total daily volume but not 1 or 2.

racket...yep..after Tue, I'm fortunate for that. Was there supposed to be a link to your post above related to the 1725 rpm pumps...would be interested in seeing more about this technology if available. Thanks! mas985...yep...I had bypass valves installed on all our pumps for this very reason...fine tuning the desired flow. That being said, I have never had a reason to open any of the bypass valves since day 1. Now, after a deep freeze last winter, I don't have the option of bypassing any more...all the bypass line froze and broke! Never thought of opening them during freezing weather...duh! Haven't repaired them yet since they weren't being used anyway. Been meaning to ask...I saw in your TFP postings, that you have a 1/2 HP 2 speed pump....is this 1/2 HP at low speed or high speed...just curious as I didn't know 2 speed pumps were available this small. Thanks!