I know that bigger is better due to friction issues. However, the bigger pipe the more pressure you lose. If you are using a pressurized filter that could be a problem. However 2" is pretty decent size pipe. How big is the pond and how many gph do you want your pump to be handling?

Revleroy the pump you are thinking of will pump about 5700 gph at 13 ft of head. I would want to keep my head at or under 13 ft to get as much water from that pump. So the question has to be how high are you pumping the water and how long of pipe. You do not lose pressure with larger pipe and it is not harder on the pump to move a larger column of water.
Mike

A 1/3 hp pump will move considerably more water with larger than 2" pipe, and it is even more important on the intake side than the discharge side. The larger water column is not a problem at all for the pump nor is there any concern with pressure loss upstream from a pressure filter. Azponder nailed it with the question on pond size and flow desired. The height of a waterfall or the presence of a pressure filter too will influence the choice of pumps.

An alternative to larger pipes is multiple pipes; Two 2" pipes have similar flow characteristics to a single 3" pipe.

Well, I plan on having a big bog filter on the top of my stream. No bead filters etc right now. The overall height gain isn't too big - probably about 5' or so.

The overall pond is ~19,000 gal, but I'm planning on using 2 1/3 hp pumps to try and get in the range of 12,000 gph pumped.

FWIW, the first pump will be hooked up to a bottom drain and pump to a lower bog filter. I'm not planning on doing fish (or at least many fish) in the pond, but at ~6' deep, I don't want the water down there getting stagnant - so I want to work the bd into my overall filtration, and not use as just an occasional drain. The lower bog will dump into the pond, almost passively (no significant height change). I figure if I do a 4" bd and run 4" pvc out to the initial filter and pump, I sholdn't have flow problems into that pump. Right?

Pump 2 will be run off a large skimmer (thoughts on great skimmers anyone), run into some basic filtration and into the pump, which will then pump up into another, higher bog that will run down a stream and waterfall into the main pond. Probably about 5' of elevation change.

Ideas on decent filters in front of the pumps to a) maximize flow b) minimize frequency of maintenence c) do the job effectively?

I always figure that I can re-work the filtration later if I decide to add more fish. At least initially, I want to have nice plants and want the ability to take an occasional dip in the water. Thanks for the feedback.

As far as initial filters go, there should be a net inside the skimmer you end up with, and possibly some matting of some sort.

The bottom drain will take in quite a bit of trash and dirt that sinks, including leaves, previously airborn dust such as pollen and dirt, and bird poop etc. You really should consider a large settling chamber off the bottom drain. The idea is to move all the bulk stuff to a central location to make it easier to remove. It could be integrated into the pond design, or set just outside the pond. You pump out of the SC to your other filtration. As the SC is gravity fed, the level in the SC remains at the same level of the pond, and the flow to it is created by lowering the level with a pump. I have about a 425 gal SC, and pump off the top third.
Even with only 800 GPH flow, a prefilter is used on the pump, and it does fill quickly with algea. I am considering some sort of barrel filter made of matting on a frame to increase cleaning cycles by increasing surface area. On that latter note, any ideas for a 2 foot diameter, 2 foot high cylinder of 1 inch matting? Currently I have only come up with a wire frame, and don't care much for that idea.

-TT

Revleroy I would think of possibilty of two bottom drains. Without a fish load this could feed directly into the pump basket. I might also think about increasing the pumps to A1/2-75's. The cost of each pump would be less than $50.00 more but would increase the flow by over 3000 gph. I might think of taking some of the water feeding the lower bog and going up to the stream to make the stream more dramatic. I would also think of two skimmers on pond this size. Please give us some dimenisions of the proposed pond.
Mike

A few fish can have a tendency to turn into many fish, through their own devices or through human input. Six feet deep sure is a desirable depth for them. I personally think a SC would be a nice addition in case fish become a bigger part of the system. They can be designed to look like another small pond; Mine has a grid of support pipes so I can place lots of plants in it. Makes it look quite nice. However, a single 4" pipe is a wit small for 6000 gph gravity feed. Two 4" BD to a single SC may be desirable. Two skimmers doesn't sound like a bad idea either. I'll confide that I'm running my system, about 15,000 gallons total, on 8000 gph from two pumps. With quite a number of plants and 22 moderate size koi it so far works great. The larger water volume ponds don't need as rapid turnover as smaller ones. I also use 4 TPRs to aid circulation in the main pond and direct debris to the BD, that helps too.

I use brush filter boxes to remove debris in front of the pumps. I service them two or three times per season and they don't seem to need it that often. They are gravity feed with 4" pipe, adequate for my moderate flow rate.

Main pond: 25' x 35' (oval-ish)
Lower bog: 15' x 15' (circle-ish)
Top bog: 10' x 10'

What about power consumption between the 1/3 and 1/2? It seems like a big jump in power consumption for a not-insignificant, yet not huge difference in flow rates.
I don't really know - tell me what you'd do!

I'll tell you what I'd do, and remind you and myself that it is MikeIL that got me started in this business just a few years back. I now know enough that I don't always agree with Mike, but Mike knows and probably always will know more than I about building a variety of ponds.

25' by 35' is a big pond, at six feet maximum depth it makes me wonder what it is for if not for fish. Taking an occasional swim in it might be fun, but probably isn't the best of ideas if there are fish in there. Certain bacteria the fish are able to tolerate have killed a few humans (perhaps immunocompromised ones, but nevertheless it isn't a comforting situation). Because this size pond would be excellent for fish, I'd make it so it could have fish. If you don't place fish in it, fine, but you will have the option. I'd remind you that fish make quite a nice combination with plants insofar as you fertilize the plants every time you feed the fish. I would design it to take two bottom drains, not because that is fully sufficient but because that will be nearly adequate and won't necessitate still more pumps. I'd shape it to have two bowls toward each end and constrict its width in the center. That gives you easier access to the pond from the sides and directs the flow pattern well. 25' wide strikes me as a bit too wide to service easily with a net (either for fish or for leaves) and I'd probably shrink that a little. Where the two bowls converge I'd make it a bit shallower, directing bottom slope to each BD at the bottom of each bowl. I'd use two BD plumbed to a single settling chamber. Separate SC are better, but I like the simplicity of one. I'd dig an in-ground SC, around 1000 gallons, and surrounded by a concrete collar. On the collar I'd place a set of pipes to hold up emergent plants such as red stem thalia, rice, elephant ears, etc. The SC would feed to one or two pumps through one or two chambers filled with brushes.

I'd use at least 4 TPRs to direct the flow in the main pond, clockwise in one end and counterclockwise in the other end. This will help direct debris to the BD. Since there will be a surface flow across the center of the pond I'd put the skimmer in the center of the long side where that flow intersects. It will help if that side is also that which prevailing winds also blow against, but it isn't mandatory.

I think you're looking for more flow than is necessary for this size pond, particularly one that contains few fish. Circulating the entire pond volume in 2 hours will be acceptable IMHO. I think even the 1/3 hp pumps are uncessesarily large. I'd try to design it so I could get by with 2 or 3 low-head pumps, though a 5' lift is getting towards their upper limit for efficiency. I'd feed my TPRs via gravity from one of the bogs (presumably gravel veggie filters) so as not to waste any pump flow.

The general design I outlined above is for a main pond primarily for fish and which feeds auxiliary ponds designed for plants. I like that plan because the fish, some of which can be rather nasty herbivores, are segregated from most or all of the plants. Since your vision probably differs, a different flow pattern may be desired. But you ask what I would do.

First, thanks for the vision, it helps a lot.

Now, stupid question: if I have a 1000 gal SC, does the water level need to be the same as the main pond? A little below? Way below?

Isn't there a risk of draining the whole pond via the BDs?

I ask mainly becasue the pond is built into a hill and retaining wall, so whatever SCs I have coming from the bottom drain will probably be anywhere from a little below pond level (say, 6" to 1' or so) to quite a bit below pond level (as much as 5 ft). This depends on where I have the BDs drain to.

Thanks bbriggs for the very undeserved but kind words. I agree with you that a pond that is 25 ft wide is a very wide pond and normally I would say it is too wide if fish were going to be kept in there. Trying to catch in a wide pond is very hard to do. But I am getting the feeling that this is meant to be a swimming pond so I would want the size. I tend to disagree with a lot of ponds about swimming in a pond. Yes there are some risks in swimming in a pond but there are risks in swimming in a lake.

This pond needs two bottom drains and two skimmers. It is my experience that people always want more water flowing than they have and that is why I suggestd 2 A1/2-75 instead of the 2 A1/3-56. Yes the electrical cost per gallon pumped is higher. Assuming that you got the max out of each pump and an electric rate of $0.10 per kilowatt than the cost for 11,300 gallons per hour with the A1/3-56 is $0.09 or .00000796 per gallon. The cost on the A1/2-75 is $0.1256 for about 15,100 gallons per hour at a cost per gallon of .00000832 per hour. Assuming that the pond is shutdown during the winter and runs 8 months a year the additional cost per year is $208 per year. I know that this sounds like a lot of money and it is but a lot of the time if it is plumbed correctly you could shut one pump down and run both for looks in which case that could save you $200 per year. But I would be willing to bet that once you see both pumps running you will keep them both running.
Mike

A SC would need to be at the same level as the pond that feeds it, high enough so it won't overflow even if the pump is shut down. They can be designed to drain a pond completely, either through accident or purpose, but many will not. Mine will take the first 3' or so, leaving 4' in the pond even if something goes badly wrong. A SC is great if fish are or will be a considerable part of your plan. To many people the fish become more important over the years. As with the waterfalls / stream, only you can truly answer what type of pond is suitable and how much flow you want to see.

I live in basically flatlands. Large waterfalls and streams are made by many hobbyists, but it strikes me they are out of place. A tranquil pond with a modest stream flow and multiple small waterfalls is closer to what one might find in nature for our area, and I therefore find that more aesthetically appealling. Running each of my pumps costs approaching $160 per year, and it's something I'm sensitive to. Even the 1/3 hp pump mentioned uses more than twice that yet moves only half again the water (under the conditions of my ponds). With 2 BD and 2 skimmers it would be possible to use 4 efficient pumps, move more water than 2 larger pumps, and have lower electrical cost. I'm not suggesting that is necessarily the most appropriate thing to do for revleroy, but it seems to merit consideration. The downside is the 5' static head, right on the border of requiring power hungry pumps.

So - the basic setup for the BDs would be this:
4" BDs --> settling chamber --> chamber w/ brushes --> pump --> bog

For the BD portion -
I can't do an in-ground due to slope. How big a sc should I get?
What type of "chamber w/ brushes" is appropriate? What size? Sources for chamber and setup?
Will I still get 6000 gph out of that?
Should I plumb everything w/ 4" pvc? on the gravity side? Will I get the flow I need?

Then, the skimmer portion:
Big Skimmer (I was thinking Savio w/ 16" wier?) --> ??? --> pump --> bog

What do I need in between the skimmer and the pump? The skimmer has basic netting etc, but what do I need on top of that for the ~6000 gph flow?

Remember to pay attention to MikeIL, a good source of information.

There are other ways to settle solids other than a pure SC, such as a vortex chamber. They can sit above ground or partially in ground and they can save space. They also can be unsightly. A possibility might be a raised SC, partially in ground and partially out. Could be made to look like a wishing well or a raised water garden. Can't really calculate the SC size without knowing its flow. For a simple SC without vortex, figure about 15 minutes dwell time. So a 6000 gph pump would require a 1500 gallon SC. A vortex can be a fraction of that, probably have to look it up as I've not used one. I love the look of dug SC, they're cheap, so that's what I have.

The filter boxes I use can be seen if you got google 'Aquatic Pond Supplies' and follow the links. Of course, if you gravity feed them they'll need to be at the same level as their source.

How you plumb things depends on how much / many pumps you select. Basically the flow rate. I split the flow of a 4000 gph pump between two 4" BD. I therefore plumbed the BD with 3" pipe (about the upper limit for gravity flow through a 3" pipe). The logic being that solids would not settle in the BD lines. A 4" line will handle around 4000 gph with acceptable draw-down. So, if you split the flow of a single approximately 6000 gph pump through two BD you will want 4" pipe to both BD. The filter chamber will handle 6000 gph, but you probably will want to plumb two 4" lines to it for ample supply.

Savio makes popular skimmers to be sure, people like their sturdy construction and their UV chambers. I went with Pondsweep because it was easier to fill them with brushes. If you follow Mike's advice you'll want two skimmers. I have the leaf net, two rows of brushes, the original mat, and a couple sieve intakes in my Pondsweep pro900. That feeds directly to a 4000 gph pump. I have had no problems with junk getting through that maze of media, nor any problems with things plugging up. The leaf net can get mighty heavy, though, when I forget about it for a few weeks in the fall.

Gotto go for now.