Pump size for small pond/bog filter/waterfall (is it doable?)

[Sugar]

I don't know anything about pond pumps, piping/plumbing or electricity, co please bear with me.

My project:
Small in-ground preformed pond, 18'' deep, 50 gallons
For bog filter: preformed liner, 15'' high, 19'' bottom and 24'' top diameter, 20 gallons

The 'bog' will be semi-buried/elevated 8'' above water surface. Filtered water will return to pond thru small preformed waterfall.

So I guess (again, I don't know anything about how it works) the water will need to be lifted 26'' (pond bottom + edge of the 'bog'), then go down to the 'bog', lifted again to the top of the waterfall = 15'' of the 'bog' total height.
If I understand well what I read so far, I need at least 100GPH pump to handle 50 gal pond, but I need to take into account the water lifting as well, so the pump will have to be bigger, right?

Thanks in advance!

 

[EricV]

You want a total water flow of about 2x the total volume of your system. My guess is that you should be looking at pumps in the 500 GPH range with this setup. But your "head height" for those calculations is just from the lowest water surface to the highest water surface. The depth doesn't matter (if you put a pump on the bottom of your pond, water pressure above it will push water into the pump giving it an assist).

 

[Sugar]

Thanks for the answer.
I am confused. The total volume is 50+20=70 gallons, so double is 140.
I understand the water lift needs to come into equation, but how?
The water will be lifted twice - first from the bottom of the pond to the top point of the bog (26'' total), then the filtered water again needs to go to the top point of the bog (15'') , so I guess both lifts must be taken into account?

 

[EricV]

I don't comprehend how one pump is supposed to lift water twice. You've got one lift with one pump from the surface of the lowest pool to where the water exits the pipe or the top of the highest pool.

Yes, I am ignoring the 140 gallons since experience tells me that while that water flow may satisfy the technical requirement of 2x volume but is unlikely to be satisfying. A garden hose is about 500 GPH. imagine 1/4 of that flow and that's what you'd get with a pump putting out only 140 GPH.

 

[combatwombat]

Agree w/ @EricV. For a submersible pump, where the pump sits doesn't matter and humps or lifts/drops in the piping doesn't matter either. The only thing that matters is the distance from the surface of the lower pool to the highest point the pump is lifting water.

So, if your pump is sending water up to the top of your bog and then going over the side of it and down to the bottom where it will output the water to be lifted again, the only 2 points that matter are the surface of the lower water and the highest point of the piping.

Pipe size and number of fittings will affect this, too. Figure out what that head height is, add a couple feet to account pressure loss from pipe and fittings, and choose your pump accordingly.

One other thing to consider is that the smaller the pond, the more critical filtration and circulation become. Mother nature likes to turn small bodies of water green. Best to massively oversize your pump and filtration. If you've ever kept an aquarium, you probably know how quickly things can get... yucky. The bigger the pond the more margin of error you get.

Like Eric said, I'd go 500 gph to be safe. A pump that size will use very little energy and you can always choke it down if you think it's too powerful. You'll never get more flow out one that's too small.

 

[Sugar]

Thanks for the answers @EricV @combatwombat !

So let me see if I understand how it works (I apologize, but I am lost when it comes to physics or anything technical, so I have to break it down for myself).

So, the pump will sit on the bottom of the pond, flexible tubing connected to its output goes to top of the 'filter' and down to piping (let's say I'll go with cross shape for my small round bog), so 2 arms of the cross shaped piping will be capped, one arm will be connected to the input tube and the 4th arm will be connected to an output tube which goes to the top of the waterfall and back to the pond.

How deep is the piping supposed to be? Some say 2 or 4 or 6 inches for 12'' bog, but others seem to prefer it at the bottom (which makes more sense to me).

 

[combatwombat]

@Sugar: Sounds about right. Have you checked out @addy1's bog building thread? More than you could ever want to know in there.

I've never heard of anyone putting their distribution piping anywhere but at the bottom of their filter. Anywhere else wouldn't seem like very good design to me.

 

[addy1]

How deep is the piping supposed to be? Some say 2 or 4 or 6 inches for 12'' bog, but others seem to prefer it at the bottom (which makes more sense to me).

My pipes are at the bottom of 2.5 feet of pea gravel

 

[GBBUDD]

You will also need a way to stop the bog from draining back into the pond when the power goes out a simple hole in the bog pipe about a inch below the gravel will work but check it now and then to insure there's no clogging.
1. This is your challlange how to get the water to fall into the lower preform without loosing water.
2 pipe goes to the bottom of the bog slits or holes in the pipe can be made to distribute the water evenly. Hole face downward.
3. Filled with 3/8 inch peastone
4.pump needs to be kept off the bottom so it will not clog so fast.
5. The 1/4inch hole below the peastone by one inch.
6. Water level needs to be kept at a few inches down so plants don't wick water out.
7. Best of luck

 

[Criscar]

Thanks for the answers @EricV @combatwombat !

So let me see if I understand how it works (I apologize, but I am lost when it comes to physics or anything technical, so I have to break it down for myself).

So, the pump will sit on the bottom of the pond, flexible tubing connected to its output goes to top of the 'filter' and down to piping (let's say I'll go with cross shape for my small round bog), so 2 arms of the cross shaped piping will be capped, one arm will be connected to the input tube and the 4th arm will be connected to an output tube which goes to the top of the waterfall and back to the pond.

How deep is the piping supposed to be? Some say 2 or 4 or 6 inches for 12'' bog, but others seem to prefer it at the bottom (which makes more sense to me).

I am a couple months ahead of you on the small pond build process. I have also used the Maccourt 20 gallon wine barrel tub with waterfall for one of my bog filters. You really don't need to use a cross arm to feed water to the bog for something so small, a single straight pipe with many small holes or slits drilled on the sides after it enters the tub and capped at the end is fine. I know people talk about the risk of gravel clogging, but I think that's less of a risk with like 20 side holes of it getting actually clogged.

The cleanest looking, least likely to cause problems way of having your plumbing enter the tub based upon my experience with this product is to use a barbed adaptor to transition from the flex tubing into hard PVC, and then use a uniseal to run the hard PVC into the tub as close to the bottom as you can safely get. I tried running flex tubing through the uniseal and as the gravel settled and such, it kept causing leaks so save yourself the trouble of having to empty 100 lbs of gravel out of the tub over and over to fix leaks and just switch to a hard PVC. I used 1" flex tubing to 1" PVC with a 1" uniseal. Also, have a heat gun handy to help you shape the waterfall edge, we had to re-work ours three times to get it to drop the water into the pond without backflow running along the rim of the tub.

I'll try to post some photos of the finished tub tomorrow, remind me if I don't

 

[Criscar]

I don't know anything about pond pumps, piping/plumbing or electricity, co please bear with me.

My project:
Small in-ground preformed pond, 18'' deep, 50 gallons
For bog filter: preformed liner, 15'' high, 19'' bottom and 24'' top diameter, 20 gallons

The 'bog' will be semi-buried/elevated 8'' above water surface. Filtered water will return to pond thru small preformed waterfall.

So I guess (again, I don't know anything about how it works) the water will need to be lifted 26'' (pond bottom + edge of the 'bog'), then go down to the 'bog', lifted again to the top of the waterfall = 15'' of the 'bog' total height.
If I understand well what I read so far, I need at least 100GPH pump to handle 50 gal pond, but I need to take into account the water lifting as well, so the pump will have to be bigger, right?

Thanks in advance!

Also, I just looked at what you wrote again and am confused as to how you plan to route the water out of the tub into the small preformed waterfall? Did you know maccourt makes a 20 gallon tub with a waterfall spillway built into it? You can get it from Home Depot and it would be infinitely simpler than trying to figure out some way of getting the water out of the tub and into the little 2 gallon waterfall form.

20 Gal. Spilway Plantainer Preformed Pond Liner

 

[CometKeith]

I don't know anything about pond pumps, piping/plumbing or electricity, co please bear with me.

My project:
Small in-ground preformed pond, 18'' deep, 50 gallons
For bog filter: preformed liner, 15'' high, 19'' bottom and 24'' top diameter, 20 gallons

The 'bog' will be semi-buried/elevated 8'' above water surface. Filtered water will return to pond thru small preformed waterfall.

So I guess (again, I don't know anything about how it works) the water will need to be lifted 26'' (pond bottom + edge of the 'bog'), then go down to the 'bog', lifted again to the top of the waterfall = 15'' of the 'bog' total height.
If I understand well what I read so far, I need at least 100GPH pump to handle 50 gal pond, but I need to take into account the water lifting as well, so the pump will have to be bigger, right?

Thanks in advance!

Hi Sugar. So I’m just wondering is your pond location constrained by size? My very first pond was a kit with a liner that held 150 gallons and to me that would be a starting size. Are you concerned about winter weather at all? If you get ice and snow you should make your pond at least 3 ft deep. Good luck with your pond!

 

[Criscar]

You will also need a way to stop the bog from draining back into the pond when the power goes out

A 20 gallon tub filled to the brim with gravel is only going to hold somewhere between 5-10 gallons of water, no? so as long as the "main" pond is only 80-90% full it should be safe even in a power outage and not overflow? There's probably a way to calculate how much water space would be left with 3/8" gravel filling a 20 gallon space but I don't know what it would be. It's still a lot of water in the bog relative to the size of the pond so may be worth playing around with pond levels to see at what point you get an overflow when you turn the pump off and on.

4.pump needs to be kept off the bottom so it will not clog so fast.

I also have my pump 1 ft off the bottom of my stock tank pond just out of paranoia that on some day I'm not home some tubing or fitting is going to rupture and I'm afraid of draining the entire pond and killing my fish if the pump was just sitting right on the bottom. At least they'd have a chance if there was still 1 foot of water left.

 

[Sugar]

@GBBUDD thanks for the notes!
Just to make sure I understand what you are talking about:
"5. The 1/4inch hole below the peastone by one inch."
so I have cross-shaped piping (four arms) at the bottom of my bog. Arm #1 is input arm, arm #2 is output arm, arms #3 and #4 are supposed to be capped.
So, in order to make that hole 1'' below gravel surface, I would connect an elbow to arms #3, run the pipe all the way up above bog surface where it will be capped (and used for cleaning - that's why above surface = I saw it somewhere) and make hole (one inch below gravel surface) to this pipe. Is that what you are talking about?

 

[GBBUDD]

5

And the first time you power goes out all your bacteria will dry out and you'll start from square one all over again