My gravel bog filter build (with pictures)

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Hello all!

I registered here in September last year after building my new pond.
https://www.gardenpondforum.com/threads/were-gonna-need-a-bigger-pond.24468/

A complete novice back then, and by now still no where near an expert.
I enjoyed reading all the comments in that thread, some of them inspired me, and all of them made me wiser.

The new pond was made with EPDM liner and my old preformed was just laying around.

Some people suggested it would make a nice bog filter, which sounded like a pretty good idea.

At the time I didn’t have the energy and resources to realize a project like this, and the whole idea remained just that, an idea. It stuck though. Over the winter I’ve been reading a lot, thinking about it and I
dismissed the whole idea more than once.
It just felt like way too much work.

But as spring arrived, it soon became clear that my puny little filter-pump was not going to keep this pond healthy and pleasing to look at.
The pond was fine during the winter, all of the fish survived (which I could have done wearing a pair of socks and some rags… some winter!)
Soon as the water started to warm a little in April, things started to get mucky and green.

Time to get to work.

Back when I made this pond, I severely underestimated the maintenance required to keep it looking clean.
Not really having the money for a fancy ready-to-go filter system, I had a go at making something of my own.
I took an old paint bucket, cleaned it, drilled 2 holes in it, fitted some bits of PVC piping and attached some flexible hose to feed water from the pond into this thing.
For filter material I tore apart an old pillow which was filled with bits of porous polyurethane or something like it.
Stuffed the paint bucket, put the lid on and hit the pump switch. Gurgle gurgle, and presto, water came out of the top end.
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And then the bucket lid launched into orbit. Turned out I made a pressure filter… Heehee! :banghead:

On the second try I placed a slab of stone on top of the lid, and just to be sure, 2 bricks on top of that.
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I guess the whole thing could have been blown to bits as the water was coming in much faster than the outlet could release it back into the pond, but to my relief and surprise it all worked out.

After a few hours without exploding paint buckets I went to bed.

Next morning the pond looked as if the pond fairy had taken out the pea soup and replaced it with spring water.
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What a delight!

But this too soon proved insufficient. The porous pillow filling stuffed in a paint bucket rapidly filled up with muck and gunk, and like my store bought filter-pump it would need cleaning every two weeks.

Next stop, gravel bog filter.

The old preformed pond had been sitting idly in it’s original location during all of this.
Halfway May I finally mustered up enough courage to tackle the bog filter idea that I was advised to build.
At first I couldn’t get my head around how to construct a thing like this.
I’m pretty handy if I say so myself, but anything with pipes, pumps and hoses was new territory.

Without so much as a clue, I made a mental sketch of what this thing would look like. I could’ve just followed one of the countless examples displayed here and elsewhere on the net, but where’s the fun in that? :cool:

I did it my way.

Went to the local DIY store, not entirely sure about what exactly I should buy. When I explained to an employee what I wanted to make and asked for his advise he looked at me in a tired manner and mumbled something like “people just make up stuff that doesn’t exist…”

Ehhhh, I’m in a do it yourself store, no? :oops:

Anyway, he did kind of help get me the parts that I needed.
I set to work with my length of PVC pipe, pipe cap, PVC elbow joint and flexible PVC hose.
And of course some PVC glue.
I used a miter saw to cut slits every 10cm and glued a cap on one end of the pipe.
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Drilled a hole into the side of my preformed pond, near the bottom. This is where the pond water feeds into the bog filter.

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Stuck the open end of the PVC pipe through the hole, glued the elbow joint to it and glued the elbow joint to the side of the preformed. Glued the flexible hose to a PVC adapter bit which then fit into the elbow joint with more glue.
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So far so good, everything stayed in position. I placed some bricks in the bottom of the preformed.
On top of them I fitted wire-fence to create a false bottom. Seemed like a good idea at the time, time will tell whether or not it was.

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I then filled up the preformed with a 100kg of gravel (black basalt and white-blueish marble for a nice contrast. This too was my own idea, again time will tell if it was a good one…

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Then I hit the pump switch.

As you can see in the pictures, everything worked so far.
The angle of the preformed was just too steep at this point.

Some adjustments later it was time to think up a way to get the water back in to the pond.
Up until this point I hadn’t thought of that.

It should come as no surprise that I’m the worst chess player in the known universe… :ROFLMAO:
I’m used to thinking up solutions and fixing problems as they arise instead of preventing them from happening.

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So, something like this.
A leftover piece of EPDM liner attached to the old preformed.
This worked for a few hours, after which I learned how difficult it is to bond EPDM to HDPE. Not funny…:rolleyes:

I foolishly left things as they were overnight, came back home the next morning to find my pond nearly drained. It had about 10cm of water left in it….:banghead:
Apparently my improvised stream and waterfall were leaking bucket loads of water on the wrong side of the wall all night long. Thankfully I got there just in time or there’d be about 15 dead fish on the bottom. I’m ashamed to tell of this horrible mistake, but I sincerely hope others may learn from it.

Anyway, time to get some plants in! Wasn’t much of a bog the way it was sitting there.
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It’s still looking pretty shitty here. Of course I didn’t think of what to do with the edge of the bog, just like I didn’t think of what to do with my pond edge. (hence the ugly brick wall, more on that later).
It’s been up and running for a few weeks now and aside from it’s filtering qualities, the bog’s been a pain in the eye.
I wanted to go for something natural looking, but yet again money threw a wrench in the works.
Things like slate and boulders are stupidly and prohibitively expensive in garden centers and can only be ordered in amounts much larger than I needed.
It’s not really laying about like pebbles on a riverbed either, boring flat lands... :sleep:
The nearest location that has what I was after is a 3+ hour drive and that’s a bit much for some pieces of stone.

As fate would have it, a good friend asked me to join him on a road trip.
Completely unexpected, our trip took us straight to slate. More slate than I could shake a stick at!
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The car we were driving was packed pretty full already, but we managed to bring back some slate and a few boulders.
Just enough to turn my pain in the eye bog filter in to something I actually like looking at.

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So far I’m pretty happy with the result.
It wasn’t overly expensive to build, adds a lovely ambience to the garden and it’s already attracting a host of insects, dragonflies, spiders and the occasional frog.
Oh and it does a pretty decent job of keeping the pond clear, which is a nice bonus!:p
It'll probably only get better as it matures.

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It turned out very well and I agree it'll only improve with maturation :)
 

addy1

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Very nice! And what a great write up! Thanks for sharing
 
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Looks fantastic!
All the surrounding stones look great and the plants will look even better as they mature. Plus, your water is clear.
I always like DYI projects. Especially using stuff you already have laying around.
I want to do a bog, but can't decide whether to use a stock tank or a liner. And since I don't have either just laying around, I'm trying to figure the most economical method.
How did you seal the pipe that enters the preform?
If you have leakage there in The future, use a bulkhead fitting.
 
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Thank you very much for the lovely replies guys. I love reading them. :love:

Very nice! And what a great write up! Thanks for sharing
Thanks addy1, it's a joy to hear that from a veteran ponder such as yourself.
I must confess I got a little carried away in writing. It seemed like a good opportunity to brush up on my English. Lol :shame:

Looks fantastic!
All the surrounding stones look great and the plants will look even better as they mature. Plus, your water is clear.
I always like DYI projects. Especially using stuff you already have laying around.
I want to do a bog, but can't decide whether to use a stock tank or a liner. And since I don't have either just laying around, I'm trying to figure the most economical method.
How did you seal the pipe that enters the preform?
If you have leakage there in The future, use a bulkhead fitting.
I'm a bit of a DIY enthusiast myself, and like you I prefer to use anything that's already around. It more often than not takes a bit of improvising, but I'm sure you'll agree that just adds to the pleasure of constructing something.. :D Love making new things out of old discarded bits and pieces. #wastenotwantnot (can't believe I did a hashtag thingy... eek!)

As for your own bog, I really couldn't tell you from experience if there's a big difference between using liner or a stock tank.
I'm guessing a stock tank would be more durable considering it's hard plastic, whereas any liner is much more prone to punctures when you fill it up with a bunch of gravel. Hopefully others can shed a light on this conundrum, and I'm quite curious about it myself.
Of course using liner would give you vastly more flexibility when it comes to shape and size. I'm storing the idea of making a bog out of liner in my thinking jelly, it's interesting.

The water supply pipe was fitted into an elbow joint which is about 1mm wider on the outside than the pipe itself. The pipe fit snugly in the hole, and the elbow joint was stuck to the side surrounding the hole. For this I used PVC glue, which I think technically speaking is more solvent than glue. It breaks apart the molecular bonds of plastics, so when they're fit together they 'weld' or 'merge' together, forming a single piece. At least that's what I came to understand, feel free to correct me, anybody.
The PVC glue is supposedly able to seal any gaps up to a millimeter as well, it was applied on both ends of the joint. On top of that, as a precaution I gave the joint and adjacent area a few coats of liquid rubber.

In hindsight, running a pipe over the wall of the bog and then down to the bottom would be a safer method. Thing is... I wanted to make the bog last year, and I hastily got started without thinking it through back in September or November last year. I drilled the hole in the side and didn't do much else with it, just left it till spring this year.
So far this haphazard approach I took has worked, but I would advise anybody who has yet to build their bog not to follow my example. :giggle:

Should it ever start to leak or rupture, my only option would be to empty at least half of the bog and remove all the dirt surrounding the joint area. It's a bit of a gamble....

Anyhow, hope this helped a little. I'd love to see what you come up with when you get around to building your bog!
It can seem like a daunting project, but it's so worth it. :)
 
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Yeah, I used to save all kinds of "junk" thinking it might be useful some day. Parts from broken down gizmos, cans and jars of nuts, bolts and other unidentifiable do-hickies. Still have most of it, but I try to not save much of it anymore. I think I still have some wheel lug nuts from my '69 Pontiac! Wish I still had that car!
There's only so much you can "save" until it becomes clutter or worse!
 
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Very nice! And what a great write up! Thanks for sharing
Yeah, I used to save all kinds of "junk" thinking it might be useful some day. Parts from broken down gizmos, cans and jars of nuts, bolts and other unidentifiable do-hickies. Still have most of it, but I try to not save much of it anymore. I think I still have some wheel lug nuts from my '69 Pontiac! Wish I still had that car!
There's only so much you can "save" until it becomes clutter or worse!
Sounds all too familiar! :D
Don't get me started on nuts and bolts, screws and washers and things like that. Even bits of scrap wood from earlier projects remain in my shed. Basically anything that's even remotely usable for who knows what and when gets to stay.
Occasionally I do find a new use for some of the "things" that lurk in my shed, but as you rightly point out after a while a lot of it just collects for the sake of collecting. I do like a clean-out once or twice a year.
 

addy1

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whereas any liner is much more prone to punctures when you fill it up with a bunch of gravel
I used some liner from bend tarp and liner. It survived our install of the pea gravel, even drove on it with the tractor with buckets of gravel. Some really tough stuff.
 
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addy1

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Basically anything that's even remotely usable for who knows what and when gets to stay.
When I moved across country, I hauled more tools, nuts bolts and rocks than anything else. Dear hubby is a keep we might need it, I can't throw out usable nuts bolts screws etc.
 
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I used some liner from bend tarp and liner. It survived our install of the pea gravel, even drove on it with the tractor with buckets of gravel. Some really tough stuff.
I guess that proves pond liner can be used to build a bog. :D
Do you remember what it was made from and how thick it is?
 

addy1

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I bought it 10 years ago, it was ppl36 now renamed. Here is their web site.

At the time the liner was rated as tougher than epdm , ie burst strength, tear etc. The deer walk the stream all winter, so far it is still doing great.

 
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