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

[Lisak1]

The key here may be "flat".

Right - more surface area would keep them from sinking.

 

[addy1]

I have flat rocks, round rocks (not small ones) around 5ish inches or bigger that have been sitting on the pea gravel for years now. Never have had to reset the rocks.

 

[stevekind]

Hi Addy - (from my earlier thread) I *think* I've cracked it. The complication arose because , as I said in my earlier post, I wanted a stream/waterfall as well as the bog filter. I know the simplest solution would have been to have the stream running from the bog overspill to the pond - unfortunately, the shape and position of the pond makes that impractical without a major re-design of that part of the garden. So, if the stream is to feed the bog i would need some sort of sump BEFORE the bog to feed the manifold under the gravel.

My latest idea is to make the bog in the shallow part of the pond using a single, continuous liner for pond and bog and building the porous, wall as you advised, laid on top of the liner. If I then put a small pre-formed pond (about 55 gallons capacity?) into the corner of the bog, with the lip *slightly* higher than the gravel, and set the stream to discharge into that. That small pond would be linked to the distribution manifold via a bottom drain . Gravity should then push the water through the manifold.

The only issue then would be flow rates - the small pond would need to be draining at approximately the same rate as it is being fed by the stream. It occurs to me though that it wouldn't matter too much if the small pool overflowed into the gravel slightly. The alternative would be to make a non-porous wall with a spillway - that should make the flow rates less critical. In that case, I could even raise the bog vet slightly in order to form a small waterfall into the main pond - though I wouldn't want to disturb the water in the main pond too much.

Hope you follow all that. What do you think?

 

[addy1]

A single liner is the best way. We made ours with one liner.

Either would work. Mine is a continuous piece of liner that goes over the bog wall and into the bog.

If you do the small pond in the bog, I would have a whole bunch of holes coming out of it near the bottom, let as much water as possible flow out into the bog gravel down low. Some over flow is no big issue.

The main thing you want is for it to have the water go up through the plants and gravel, as much as possible. I had a top flow "bog" one time, ie water flowing over the gravel not up though. The surface of the gravel constantly clogged up with muck. I had a low drain coming out, most of the time no water came out it the water just flowed over the edge of the container.

The porous wall bog would have water flowing out into the pond but also some of the pond water would wander back though the wall. Unless you had a large flow of water out though the wall. When I was doing my "study" of bogs, tons of internet reading, the porous wall bog could also be built without water being fed into it, the pond water would wander though the wall and back out.

But imho, pushing some water flow through the gavel is the best way to get the bog doing a good filter job.

I just know when I built my pond with the bog as the only filter, a lot of people said it would never work. Glad I didn't listen, lol, my pond is a almost zero maintenance pond. The maintenance I do is yanking plants from the bog, they grow too good, grooming lilies. OW I can ignore it most of the time.

 

[stevekind]

Many thanks Addy, that is really helpful. Going to go with the preformed pond liner idea for the sump and a solid wall with an overspill for the bog. Going to spend part of today remeasuring the hole and working out the exact volume of water plus any additional volume such as the stream course. Thinking possibly of a variable flow pump depending on the numbers. Will order all the kit during the holidays and be ready to go on construction first week in January providing the ground isn't frozen. No time to waste - If the winter here is mild the frogs will be back looking for a home in February!

 

[addy1]

Enjoy! You will find that the pea gravel will settle once it is running. I added a bunch of bags after the fact. I also did not rinse it. I had way to much to rinse, and that year we were in a sort of drought. Did not want to wipe out our well. The fine dust was nicely removed by the bog.

You will also find out that the surface of the bog, over the years, will start to get a layer of muck as it runs. I just ignore it. At one time I was thinking of using a vac to remove it and never got around to pass the thinking stage.

One thing I would suggest, is make the wall of your bog higher than you think it should be. I added around 2 inches to the wall after the build. Always leave your excess liner, fold under, bury but do not cut.

I use just one external pump. Hauled it from my Arizona pond. Per my soft guess work on volume of water in my ponds, I circulate the water about once every hour and a half.

 

[Lisak1]

Going to go with the preformed pond liner idea for the sump and a solid wall with an overspill for the bog.

I think @addy1 covered most of your questions, but I did want to add that I would never opt for a preformed over an EPDM liner. The amount of work it takes to get one to be level and stay level just wouldn't be worth it to me. Plus over time they are prone to cracking, especially if you have any heaving or shifting in your ground which I'm assuming you would in 6B.

Just thought I would throw that out there. Maybe you have a reason for using a preformed and I missed it - if so, just ignore me!

 

[Ronfire]

One idea I was thinking of was to have a top pond flow down into a lower bog. Have a wall in the lower bog to section it off to collect the water and have pipes from the bottom of it feeding into the bottom of the bog. Then have a skimmer at the other end with a pump to return the water to the pond above. Might still do this idea once I start my build.

 

[stevekind]

I think @addy1 covered most of your questions, but I did want to add that I would never opt for a preformed over an EPDM liner. The amount of work it takes to get one to be level and stay level just wouldn't be worth it to me. Plus over time they are prone to cracking, especially if you have any heaving or shifting in your ground which I'm assuming you would in 6B.

Just thought I would throw that out there. Maybe you have a reason for using a preformed and I missed it - if so, just ignore me!

Thanks for the suggestion Lisa - I'm not overly worried about the pre-formed pond shifting or cracking - we are in a very sheltered site and I don't think I have ever seen serious freezing of the ground to any depth in the 35 years we have been here (I think we are in zone 9, not 6B - perhaps I filled my profile incorrectly). Also - the preformed pond will actually be sitting in the corner of the bog and should be very easy to replace if there is any problem. But thanks anyway for the advice

 

[Lisak1]

I think we are in zone 9, not 6B

Ah! Totally different then!

 

[stevekind]

Hi Addy - Sorry to be so long posting an update - I'm still having troub;e with the forum allowing me to post. Hopefully, it's in a good mood today!

Here are some images of the current state of my project - the pond is filled, the water is moving

 

[addy1]

Very nice! great on getting the water running!

 

[stevekind]

Here's a shot from the other end. Hopefully, the exposed bits of black liner will be covered eventually by plants either growing up or trailing down

 

[stevekind]

No plants in the bog filter as yet - we're currently having a run of freezing nights here - ice on both the main pond and the mini-pond/sump

As you see, water is currently being delivered to the mini pond via a pipe. Mext stage is to build the stream the will discharge into the mini pond.

 

[addy1]

The plants will hide a lot. During winter I see a bit of liner in my bog as soon as the plants start to grow.............gone