Does the porous retaining wall as a partition work well?

[Reddevill]

I've had an above ground pond for years in Michigan, zone 5, with much success so far. The fish live in it over the winter with a trough heater, no filtration in winter. I'm adding in a Gravel bog filter this spring since I have to make the pond larger anyway. I've read that using a porous retaining wall between the pond and the gravel seep the filtered water adequately into the pond; instead of using a waterfall or something similar. Did anyone find that this did not work well for them?

 

[JamieB]

I haven’t seen a design like that so far. My first thought is that it would work, however, the second is that the brick you use must be well researched, and probably well aged, as I know some might have substances leach out.

 

[Mmathis]

Hello and welcome!

I must be imagining things, but I thought that we recently had a similar thread posted.

 

[j.w]

@Reddevill

 

[Jhn]

My main concern would be water following the path of least resistance and how much contact/dwell time in the bog with the plants/roots would it maintain as the plants grow and spread causing channeling to the easiest path through the porous wall. One of the main benefits of a bog is plants pulling nutrients from the water, if the plants arent getting much contact with nutrient rich pond water it will lose some benefit from a traditional up flow bog where water flows up through the gravel then into the pond.

 

[Reddevill]

Thank you for your reply! I wasn't very clear, the bog will be fed water from the pond via pump to the bog distribution pipe under the gravel, then seeps through the porous retaining wall back into the pond. It looks very interesting and I requested to know what Porous retaining wall material they used but thought someone else may have used this method too. You bring up a good point, how fast would it seep through the wall....

 

[GBBUDD]

I saw a few posts regarding the porous bog wall between the bog and the pond. I have seen one where they led the reader to believe that water leaching through the wall would clean the water. While if it was a cinder block wall they would be correct the water that made it's way through the block would pretty much be free of any organics or sediment in the water. However as @Jhn stated water will flow to the weakest point the path of least resistance and that will not be your wall. while some water will always leach through the wall . it will never be enough to do much of anything. it won't hurt but it's not going to help much either. With that said if you build the wall between out of cinderblock or even wood " which is another story" you'll want to plan that 90% of the water in a correctly built wall will raise up through a foot or more of stone much faster then it will through a cinderblock . You have an area where the water is being pushed upward and in doing so it also using that energy for a water fall is a no brainer. i have yet to see someone " WHO DIDN'T HAVE A LEAK DUE TO A BAD DESIGN..... Have a regret to building a waterfall . Now have some regretted not digging into the nuts and bolts of a water fall to figure if they want a quiet water fall or if they want a water fall that will drown out the sounds of a highway. That can be an issue that people don't think about.

 

[poconojoe]

When I added my bog onto the pond, I lifted the existing liner I had under my previous waterfall and pulled it back. I built my wall out of cobble stones (Begian blocks) that I had laying around. I set the blocks right on the ground. I used clay soil as mortar to make the blocks fit together in a stable manner.
I left out two blocks in the middle of the top course for the water to return to the pond.
I then took that existing liner and draped it over the wall. Then I layed the new bog liner over that. I overlapped the liner by about 2 feet. Then hid all the liner material with big stones.

So, my wall is wrapped in two liners and supported by big stones on the pond side and gravel and water on the bog side. That wall is about 20"-24" high and not going anywhere.

I think you can use just about any block you choose. Probably the most common would be concrete block (usually mislabeled as cinder block). I don't think they make "cinder block" anymore. That used to be common when most buildings were heated by coal and a lot of coal cinders were available.

As far as a porous block, I couldn't even give you an idea as to what that might be. Maybe check a mason supply yard.

My return water area isn't much of a waterfall. It's way lower than my original waterfall, but it doesn't bother me.

 

[addy1]

My flat rock water fall from the bog to the pond is about 6-10 inches high depending on how full the pond is. The arrow points to the bog wall

 

[poconojoe]

Here's mine. I planted parrots feather in the gravel and let it hang/grow in the area where the water returns to the pond..