Bog building, also called upflow filter, eco filter, wetland filter

[Ronfire]

If you build the bog with 12" of gravel and then allow 4" of water and 2" above that you could ma max size of 4.5 x 4.5 ft.
That is pushing it to the max for the liner with nothing to spare. if it is round shaped you could use a corner for the return to the pond. best to plan closer to a 4' max.

 

[poconojoe]

If you build the bog with 12" of gravel and then allow 4" of water and 2" above that you could ma max size of 4.5 x 4.5 ft.
That is pushing it to the max for the liner with nothing to spare. if it is round shaped you could use a corner for the return to the pond. best to plan closer to a 4' max.

Ok, I have some questions now..I'm learning too!

So the bog needs 12" of gravel as stated by most. I would think you would want the gravel filled to the very top as to conceal all of the liner. Although, you could always stack stones on top of the gravel to hide any liner.

Then you're going to have a low point or spillway where the water returns to the pond.
You're saying you only need about 4" of water in the bog? So you'll have 8" from the lowest point of the spillway to the highest point of the bog that will be just gravel?
I thought the water in the bog would be deeper. Maybe more like 8" as a guess. That would leave a 4" difference. Probably enough to ensure the water flows over the spillway and not the sides of the bog.
I guess what I'm asking is... what is the consensus on how deep the water should be in a bog that has 12" of gravel ?
And as far as the spillway width, I guess it depends on pump size, how much water volume you expect to flow over it and what effect you desire. I guess if it's narrow you would get a more turbulant rush of water compared to a wider more gentle flow.

 

[Lisak1]

I'm not sure I understand your whole question, but I'll add my two cents anyway!

For reference, our bog is a full four feet deep. WAAAAAYYY deeper than recommended by most anyone, but you know what - it works great. The bottom has several (can't remember how many exactly - I should figure that out someday!) Aquablox, and a centipede and snorkel, then there's a layer of softball sized boulders, then there's large gravel, then smaller gravel. I don't know where you heard 12 inches of gravel was the norm - maybe I missed something in this thread - it is epic!

Are you asking how much water should be above the gravel?

 

[poconojoe]

I'm not sure I understand your whole question, but I'll add my two cents anyway!

For reference, our bog is a full four feet deep. WAAAAAYYY deeper than recommended by most anyone, but you know what - it works great. The bottom has several (can't remember how many exactly - I should figure that out someday!) Aquablox, and a centipede and snorkel, then there's a layer of softball sized boulders, then there's large gravel, then smaller gravel. I don't know where you heard 12 inches of gravel was the norm - maybe I missed something in this thread - it is epic!

Are you asking how much water should be above the gravel?

Im probably over thinking this whole thing. I do that a lot!
And I think I can now answer my own question too!
My question was...in a bog that has 12" of gravel, how deep should the actual water table be?
But from your question, I recall some people have the water above the gravel as well as others having it below. So I guess it's up to the owner.

I find it interesting that your bog is so deep. It makes me wonder why 99% of what I've read states maximum 12". I'm wondering why it would even matter. As long as your plant roots can reach the water, and there's enough surface area for plenty of plants, why would gravel depth matter?
What are the surface dimensions of your bog? Is it equal to the recommended 30% of pond surface? If not, and your bog works great, then I might go that route...deeper and not as wide...

 

[addy1]

Mine is 2.5 feet deep, some places water over the gravel, some places water under the gravel. 26-27 feet long 4ish feet wide. Way over grown, like usual. The wall between the bog and pond was supposed to stay dry............nope water trickles over it here and there and flows over the water fall.

It is around 30% the size of the pond.

Now my hot tub pond, with a mini bog, like a planter, has pea gravel and plants in it. Water up from the bottom trickles back into the pond, that is maybe 1% the size of the hot tub and it keeps the water clean, that and the other plants in the pond. All work together.

 

[Tula]

If you build the bog with 12" of gravel and then allow 4" of water and 2" above that you could ma max size of 4.5 x 4.5 ft.
That is pushing it to the max for the liner with nothing to spare. if it is round shaped you could use a corner for the return to the pond. best to plan closer to a 4' max.

Thank you so much, I really appreciate the information ! A 4 foot circle may be all I have room for, I'll measure later today. Again, thank you very much

 

[Tula]

Mine is 2.5 feet deep, some places water over the gravel, some places water under the gravel. 26-27 feet long 4ish feet wide. Way over grown, like usual. The wall between the bog and pond was supposed to stay dry............nope water trickles over it here and there and flows over the water fall.

It is around 30% the size of the pond.

Now my hot tub pond, with a mini bog, like a planter, has pea gravel and plants in it. Water up from the bottom trickles back into the pond, that is maybe 1% the size of the hot tub and it keeps the water clean, that and the other plants in the pond. All work together.

I'm still very tempted to do something like this and use my resin half barrel. The one reason I think about doing an ingroud bog, is to better the chances of the bog plants over wintering. How do you plants come out of winter in your mini bog?

 

[addy1]

I'm still very tempted to do something like this and use my resin half barrel. The one reason I think about doing an ingroud bog, is to better the chances of the bog plants over wintering. How do you plants come out of winter in your mini bog?

This is the first winter, my guess is they will die, since I will have nothing running. But it is just water willow of which I have a ton. My in ground bog all of the plants survive, but the gravel is never dry but it does freeze. At least down xx inches

 

[poconojoe]

Thank you so much, I really appreciate the information ! A 4 foot circle may be all I have room for, I'll measure later today. Again, thank you very much

I suggest you dig as wide as you have room for. Get it all set (height and level), then measure for the liner. This way you get the most out of your space and it may be the best way to purchase the proper size liner.
Anyway, that's what my plans are. If I ever get to it! Ha!

 

[addy1]

I had to build up the slope to make a flat spot for the bog. 8 foot high dirt berm. Left just enough room to get our mower through between the dirt, the fence and maple tree.

 

[Lisak1]

Im probably over thinking this whole thing. I do that a lot!
And I think I can now answer my own question too!
My question was...in a bog that has 12" of gravel, how deep should the actual water table be?
But from your question, I recall some people have the water above the gravel as well as others having it below. So I guess it's up to the owner.

I find it interesting that your bog is so deep. It makes me wonder why 99% of what I've read states maximum 12". I'm wondering why it would even matter. As long as your plant roots can reach the water, and there's enough surface area for plenty of plants, why would gravel depth matter?
What are the surface dimensions of your bog? Is it equal to the recommended 30% of pond surface? If not, and your bog works great, then I might go that route...deeper and not as wide...

I guess we didn't do a whole lot of research on how deep the bog should be. (My boys would have preferred a lot less digging, I can tell you that!) We built it to accommodate the snorkel and centipede which required the four foot depth. Ours is 24 square feet, which is about 10% of our pond surface area. Again, I don't know if there's a whole lot of research behind any of these numbers - we were told 10% for garden pond, 30% for koi pond. Essentially we made ours as long and wide as we could in the space we had.

I think people have a concern that deeper gravel will get filled with muck or debris or be difficult to clean. We haven't found that to be the case and in fact have never had to clean our bog in 8 years. And you're correct - how much water, if any, is over the gravel is really more personal preference. The only concern would be if the water were too deep for bog plants to grow. Most don't want to be submerged too deep in the water. I move my gravel around a lot to plant things and hold things in place until they get rooted. It's fun to plant in gravel and water - much more forgiving than dirt!

 

[Spanky]

I apologize if the following questions have been addressed in this thread already. I have done the searches and have found either conflicting answers or no answers, so here goes;

My bog will be 12" deep pea gravel. Does the size of the gravel matter? Bagged gravel from the big box store OK?

Can I use 1 1/2" pvc grey schedule 40 electrical conduit for the water distribution under the gravel? I like the large sweep 90 degree elbows that you cannot get in white plumbing pvc due to less flow restriction. Plus, I'm building a raised bog and the piping must come up from outside the wall and down into the bottom of the bog. The grey conduit is UV resistant.

Can I combine the schedule 40 electrical conduit and white plumbing pvc? The transition fitting from the flex hose to the rigid piping is only available in white pvc. If so, should I use standard plumbing pvc primer and cement?

I will definitely use the black mesh net in my skimmer. Would the use of the provided mechanical media mat be too much filtration thus starving the bog?

I just cannot seem to grasp the utility of a vertical clean out pipe at the end of my pvc distribution grid. If I stick a garden hose down a 1 1/2" pipe and turn it on full blast it will be a geyser out the top while doing nothing to clean out the clogged bottom piping. How does that work exactly?

Thanks in advance for being patient with this garden pond newbie.

 

[poconojoe]

From what I have read, 3/8" pea gravel is what should be used.
Concerning the long sweeping elbows, I suggest you stick with plumbing pipe. Electrical conduit is not meant to hold water pressure and the walls are not as thick as the plumbing pipe. I strongly suggest you take a look at black schedule 40 flex PVC. It's not real flexible, but will cure your concerns with tight turns and will enable you to use less rigid fittings. You can bend it in a gradual fashion, plus it can be glued to normal rigid schedule 40 PVC fittings.
So, I would use the flex stuff from the pump to your under gravel manifold and make the manifold out of rigid (schedule 40) pvc.

 

[addy1]

Electrical conduit is not meant to hold water pressure and the walls are not as thick as the plumbing pipe.

When it is for bog piping there is no water pressure, since we cut holes all over the pipe. Ours is full of slits.

I just cannot seem to grasp the utility of a vertical clean out pipe at the end of my pvc distribution grid.

I didn't put one in, hubby decided we didn't need it and 9 years later still have not needed it.
But my gravel is deep, I have not had roots or anything get in my pipes and clog them.

My bog will be 12" deep pea gravel. Does the size of the gravel matter? Bagged gravel from the big box store OK?

I used the pea gravel in the construction area of home depot. Cheaper than the garden area pea gravel.

 

[Lisak1]

ANY gravel is fine. The purpose of the gravel it two fold - to give the plants something to root into and to give the bacteria something to colonize. Neither the plants nor the bacteria care one bit where you buy your gravel. We've also found different types of gravel called "pea gravel". Some was very, very tiny - barely bigger than sand - and others was closer to the size of a raisin. Our "pea gravel" is exactly that - the size of a pea.

We don't have an actual clean out in our bog either. We have a pump vault that we could use if we needed to, but have never had the need.

But seriously - I think people overthink a lot of these things. Nature is very forgiving. These are man made bogs with lots of man made rules. Get the general principles in place and it will work.