How big a bog can I run with my spare pump?


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I'm working out the design for a upflow bog at the moment. It will sit near the boundary of the pond and feed water off the top and back into the pond. I am planning to run this using a spare submersible pump. This will supplement the existing pressure filter I have running with separate pumps.

The pump I hope to use is a Laguna PowerClear 3500. When designing the bog, though, I'm not sure how big I can make it. I am picturing the pump trying to push water up and out of the pond, and then through gravel into a potentially big container. Surely all that backward pressure from the water would eventually put a strain on the pump?
 
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My pump is rated for 6800 gph If I recall right, I have had it for over 20 years. It pumps directly into the bog and there has been no issue with back pressure. Water will find a way. Per the "rules" my pump might be stronger than suggested for a bog type filter. But due to the size it might be just right (ie size of the bog) I never cared just used the pump I had, set it up and all has been working for many years.
I get a good flow throughout the bog. Great waterfall back into the bog and trickle flow over the entire bog wall, 26ish feet.

It is technically too small ie gph for the ponds. IE total water it is filtering, I turn over the pond water about every 2 plus hours. The pond still stays in great shape due to the bog.
 

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A lot depends on the size of the outflow on the bog. My bog is only 11x3 and I run a 1600gph pump. Anything bigger and the bog overflows over the outside edges. Make your outflow to the pond big enough to handle the pump volume.
 
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My bog is 2.75x6x 1foot deep (approximately) on the side of a 9x9 foot (square, formal) pond which varies from 40" to 18inches in depth. I use a 2800 gph pump that sits on one of the 18" deep shelves ("in case something goes wrong, the pond won't completely empty"). I used 1.5 inch flex PVC from pump to bog, which has a single 1.5 inch rigid PVC on the bottom, slits half-way through the pipe that runs the length of the bog under the pea gravel. The water flows over part of the long side of the bog, not too fast and doesn't "drop" too far, because I find the sound of ever-rushing water to be annoying. I manage the water coming out of the bog by using larger stones to block some of the outflow. I haven't had to tinker much in the 4-5 months it has been running (the plants have doubled in size, so I'll have to do some tinkering on that fairly soon.)
I've attached a picture, assuming that would help.
 

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My little secondary pump isn't in the same league it seems. Just 580g/ph, 18W.

I guess I could try, I was going to just do a little bog in a 100L bucket and see if it helped up the biofiltration enough to complement the existing mechanical pressure cannister filter.

Can anyone suggest an "idiot proof" video for me with an ideal container type bog build? I'm not very handy and need lots of guidance. I'm also not sure how to go about attaching the pump to the bog, e.g. what size tubing and how to get to that size.

Alternatively is there any value in getting a box type filter and packing it with gravel rather than the usual bioballs? This would save me a lot of the handy work I'm finding a bit intimidating.
 
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My little secondary pump isn't in the same league it seems. Just 580g/ph, 18W.

I guess I could try, I was going to just do a little bog in a 100L bucket and see if it helped up the biofiltration enough to complement the existing mechanical pressure cannister filter.

Can anyone suggest an "idiot proof" video for me with an ideal container type bog build? I'm not very handy and need lots of guidance. I'm also not sure how to go about attaching the pump to the bog, e.g. what size tubing and how to get to that size.

Alternatively is there any value in getting a box type filter and packing it with gravel rather than the usual bioballs? This would save me a lot of the handy work I'm finding a bit intimidating.

tis simple; buy wood, build box to size. line box, put in pvc pipe on bottom, pea gravel next; voila! done! Yeah, yeah, there's details, but that's the gist of it.

Use pressure treated wood, make box at least 18" deep; 12" for pea gravel and 6" for probably rising water level in bog box. Consider what you want your 'back pour to your pond'/waterfall to look like. Most create a slot/weir/pipes for this purpose. Make this with some slack in mind as you might need to increase the weir openings depending on how much water you send to it.

Line box with EPDM or HDRPE; no vinyl

Manifold pipe; made from PVC; has slits cut, every 4-6", cut ONE-THIRD the way through pipe - this is for water egress. Pipe is ususally 2-4" in diam. You'll use pvc fittings to mate your pump hose to this manifold. You can either go through your box or over. Through needs fittings, over does not. Provide a valve you can open to break the siphon, or drill a small hole at the top of your tubing to do the same function.

Fill with round stone. 3/8" pea gravel is the norm. If you want, you can make this box bigger/deeper and add graduated layers of round stone; large on bottom, smallest on top.


That's basically it.
 
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That all makes sense, but I do get stuck in the details.

  1. I don't quite get the part about providing a valve/hole to break the siphon. If this is in the inlet piping, won't water being pumped in also leak out of this?
  2. Do I need to make a clearance between the bottom and the start of the gravel? Some designs include this (e.g. using aquablox), seemingly to allow sediment to collect at the bottom. I know some use large rocks at the bottom for this purpose but I just imagine the pea gravel filling in the gaps.
  3. Do I need to split and run multiple PVC pipes into a manifold along the bottom? Some designs seem to do this, but it looks like it would make it much more complex, especially if it ever needs cleaning out.
  4. 2" is quite a bit bigger than the outlet on the pump I'm trying to use. Will this matter?, and if not, I wonder how it's recommended to step the size up to connect? I'll need to run soft tubing up to the start of the PVC piping. (Just found the kinds of fittings needed to attach to PVC, I think that answers that question, thank you!
  5. Is a cleanout valve recommended? Also not quite sure how these work.
Since I want to make it in a plastic container that's dense enough to hold the weight of the gravel + water, that takes away the worries of trying to build a box and source liner at least!

Given where I am going to position this trial bog, I'll probably need to use a pipe to return. This looks like it just needs a bulkhead fitting, larger gague of PVC than going in (to avoid overflowing), and needs to be positioned at the top of the water level - so I think I'm good for that last bit.
 
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That all makes sense, but I do get stuck in the details.

  1. I don't quite get the part about providing a valve/hole to break the siphon. If this is in the inlet piping, won't water being pumped in also leak out of this?
  2. Do I need to make a clearance between the bottom and the start of the gravel? Some designs include this (e.g. using aquablox), seemingly to allow sediment to collect at the bottom. I know some use large rocks at the bottom for this purpose but I just imagine the pea gravel filling in the gaps.
  3. Do I need to split and run multiple PVC pipes into a manifold along the bottom? Some designs seem to do this, but it looks like it would make it much more complex, especially if it ever needs cleaning out.
  4. 2" is quite a bit bigger than the outlet on the pump I'm trying to use. Will this matter?, and if not, I wonder how it's recommended to step the size up to connect? I'll need to run soft tubing up to the start of the PVC piping. (Just found the kinds of fittings needed to attach to PVC, I think that answers that question, thank you!
  5. Is a cleanout valve recommended? Also not quite sure how these work.
Since I want to make it in a plastic container that's dense enough to hold the weight of the gravel + water, that takes away the worries of trying to build a box and source liner at least!

Given where I am going to position this trial bog, I'll probably need to use a pipe to return. This looks like it just needs a bulkhead fitting, larger gague of PVC than going in (to avoid overflowing), and needs to be positioned at the top of the water level - so I think I'm good for that last bit.

okies, let me help clarify;

1. yes, water WiLL come out but barely; you're talking about a hole 1/4" AND this hole + pipe is OVER your bog, so no water loss/leakage. It's the poor man's solution to adding a tee and valve to this same pipe (from your pump)

2. you have choices; it's been done both ways with varying degrees of benefit. Aquablox give you a volume/space where water can slow down and any debris can accumlate apart from your gravel. Using large rocks instead (which is what I did) gives you similiar but without the largeness of space. That is, my large rock layer slows the water down but has large openings for upward travel. Aquablox are expensive, large round 8" boulders are not. MOST use 2" pvc for their manifole, I used 4" corrugated drain pipe/tile. Both have slits cut 1/3 the way through the manifold. With aquablox, you typically also use a snorkel for cleanout purposes. In my case, I used a DIY snorkel (can you see I'm on the cheap side when I can be???). Function is exactly the same here.

I have some bog construction pics in my showcase; year 2019

3. no, you can do one line. Sort of depends on your bog shape/layout. For instance, in MY bog, it's 3' wide. Again, I use 4" pipe, NOT 2" pvc. I used (2) leads right down the middle and each is 4". Some do branches etc but it's not necessary. More even water distribution can be beneficial but it's MY belief the water will find the easiest path up anyhow, so once out of your manifold, it'll flow sideways and find those channels eventually. See, over time, crud will stick to the bottom of the pea gravel layer and water will be diverted until it decays enough to allow flow again. The water finds a way, trust me.

4. yes, there are pvc adaptors; you're good.

5. okay, this is one very important detail IF you want a cleanout; when you dig your bog (or even make one out of wood), you have to make one point the 'low' point. When cleaning out a bog, you FORCE water (a lot of volume a sustained pressure) down into the TOP of your bog. The water flows backwards and down, clearing the pathways. ALL this 'bad' water now has to go somewhere, hence the cleanout. Putting this cleanout at the low point guarantees all this crud+water ends up there. INTO this cleanout, you will have a secondary pump. As you force water down through your bog top, you' also pump the dirty water out the cleanout. So, two pumps. IF you're going to dig this, another important pont is to shape your bog walls like a 'V'; this too forces the bad water down to your low point.

What you'll find is IF your bog water level rises faster than it can get out (of your pipe), you'll be needing to put in more pipes. General rule of thumb is outlet size diam = twice the inlet size. So if 2" in from pump, 4" out, or have (2) 2" outlet pipes. What I did with my basement mini bog is use a mason plastic mortar box, 3'x2'x8". I cut and heat shaped a weir on one side that is about an inch lower than the top fo the mortar box. So, water rises up through the gravel and before it reaches the top, it pours out the weir blade. I have my mini bog overhanging my winter pool and it just flows out and over the edge like a sheet waterfall. I can attach a pic...brb

I'd not bother with cleanout, snorkel, aquablox or large bouders unless you are doing something large. Pot type bog filters don't need such as they're easier to clean/mess with.


2022_0110_141747_001.jpg


2022_0110_141807_004.jpg



I have my pump going to the black garbage can where a bunch of bioballs are; they fill up, overflow into an outlet pipe (the white pvc) and then down into the mini bog to it's manifold. I used to have a prefilter in the garbage can but nixed the idea for more biofiltering. I just set it up a week ago, so plants are still getting going. Second pic shows the weir blade waterfall I cut and heat shaped.


Okay, that wasn't so bad, now was it?

:cool::p:p
 
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The over all idea is to have a bog that is 30% of the size of the surface area of the pond. With a pump that can turn over your pond between 1 1/2 times an hour to once an hour or for larger ponds that can become once every two hours . Larger meaning over 15 or 20,000 gallons. Depends on how bio loaded you make your pond " how many fish what size are they and how often and how much you feed them " The idea to a bog whether it has aquablox or is just a pea stone bog is to SLOWLY push water through the bog. so you would not want to push 6000 gallons and hour through a small 2 foot wide by 4 foot long bog . My belief is to have an over sized bog and push more water through a larger bog but one that still allows
  1. I don't quite get the part about providing a valve/hole to break the siphon. If this is in the inlet piping, won't water being pumped in also leak out of this?
    There are three was to do this.
    1. drill a hole in the pipe where water will spray out as the pump in on but when the pump goes out the air gets into the pipe and breaks the syphon

    2. is a check valve i have found these to be even less reliable unless you can give a good deal of head pressure to them they leak and eventually drain out exactly what your trying to prevent.
    3. Lastly is my choice that being a vacuum breaker it is in the same idea of a check valve but when the pump is on it forces a flap to close and pushing it closed keeping the water going where you need it to but when the power goes out the flap drops allowing air in and breaking the syphon.
  2. Do I need to make a clearance between the bottom and the start of the gravel? Some designs include this (e.g. using aquablox), seemingly to allow sediment to collect at the bottom. I know some use large rocks at the bottom for this purpose but I just imagine the pea gravel filling in the gaps.
  3. Do I need to split and run multiple PVC pipes into a manifold along the bottom? Some designs seem to do this, but it looks like it would make it much more complex, especially if it ever needs cleaning out.
  4. 2" is quite a bit bigger than the outlet on the pump I'm trying to use. Will this matter?, and if not, I wonder how it's recommended to step the size up to connect? I'll need to run soft tubing up to the start of the PVC piping. (Just found the kinds of fittings needed to attach to PVC, I think that answers that question, thank you!
  5. Is a cleanout valve recommended? Also not quite sure how these work.
the water to sit in the bog and let mother natures creatures bacteria micro organisms and such do there job consuming any left over food or plant matter.
 
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I think it depends on the size of the bog.

To give you an example:
My bog is 14 feet X 5 feet and has 12 inches of gravel. Well, it's actually river stone. I couldn't get pea gravel at the time, so I used smooth river stone.
My pump is 3650 gallons per hour and it seems perfect. Not too fast and not too slow.

You don't want the flow to be too fast. You want the water to slowly work it's way through all that surface area that the gravel provides. I would think I'd rather have it a bit slower than having it too fast.

Funny how the bog criteria in general has a lot of leeway. A lot of people have not followed the "rules" and their bog has done just fine.
 
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As stated by others, the size of the return from your bog to the pond is important. If it's too small, the bog might fill up and overflow. It's best to have it a bit bigger than you would think or better yet, have it so you can enlarge it afterwards if needed.

If your return is a spillway and you feel it's too big and the flow is not to your liking, you can always just lay some large rocks within the spillway to increase the water disturbance to your liking.

You could also add a wye fitting to your pump's output. Then have a ball valve on each branch of the wye. One branch can feed the bog and the other can go back to the pond or feed another filter. With this setup you can fine tune how much water goes to the bog by adjusting the ball valves.

Adding more stones within the spillway can also raise the water level in the bog, if you like. Some people like a little water above the pea gravel, some don't.
You can also have it both ways. Have high and low spots in the gravel either for looks or to accommodate different types of plants.
 
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1. yes, water WiLL come out but barely; you're talking about a hole 1/4" AND this hole + pipe is OVER your bog, so no water loss/leakage. It's the poor man's solution to adding a tee and valve to this same pipe (from your pump)
My piping is nearly done. Before I go and ruin everything, I just wanted to check - do I drill this little hole in the side of the pipe feeding into the bog? (Picture attached)
 

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Well actually there is no photo attached... but I can answer without the photo. You CAN drill the hole, but you don't HAVE to drill the hole. However you want the hole at the TOP of the pipe, not the side. Wherever the pipe is horizontal is a good spot to drill it. And preferably where it will run back into the bog if it leaks.
 
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My piping is nearly done. Before I go and ruin everything, I just wanted to check - do I drill this little hole in the side of the pipe feeding into the bog? (Picture attached)
I'd put it at the top/highest point and aimed toward the bog, or even aimed up. The hole has to be higher than the bog water level. The idea is to break the siphon when you power down the pump. Did you cut slits 1/3 the way through your horizontal bottom pvc pieces? I generally face them up but other face them down. I do it this way to guarantee no blockage by sediment/debris. Eventually, such will collect in the pipes and you may have to blow it out, hence the vertical pipes with caps (should be removable to allow this cleaning process). Too, have a union (not a coupler) between the pipe feed from your pump and the pipe going into your bog. This will allow you easier separation if/when you ever need to mess with anything in the bog container.
 
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Picture is showing here . the hole your talking about is to break the siphon if your power goes out. SOOOOO that hole is to be installed right at the gravel line . this way when the pump is on and water is spraying out the water is caught by the bog. I would place larger rocks around it to keep the splash down and keep anything from clogging it up.
 
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