Question about concrete block bog filter

[GaryMoz]

Yup. I had no idea what you were referring to by sleepers.

Here in the states a sleeper is a railcar with sleeping accomodations.

I'm on the other side of the pond and recently learned loo, swipes, knackered and chinwag.

The overnight sleeper is still a train with sleeping coaches.

You can't beat a good old chinwag over the garden fence.

I'm knackered now, I've been working on the pond all day, but I've got to nip to the loo now for a jimmy riddle

 

[GBBUDD]

color me pink! WTF did i just say! opps it's tickle me pink isn't that how much i say that..

 

[drjay9051]

Jimmy riddle cockney for piss (piddle).
Learn something new everyday!!

 

[tinycat]

I will be building a new bog filter with dimensions of 25x6. It will be built with concrete (cinder) blocks and total height will be 24 inches. I plan on having the gravel in the bog at a depth of about 12-14 inches. Most of my information came from the following link https://nelsonwatergardens.com/gravel-bog-filter-construction/

My only real concern are the walls of the bog.

Everything I have read regarding "retaining walls" and similar structures state that you must have a pored concrete footer to assure stability.Without a poured concrete footer you risk instability and collapse, or so they say.

Now since this will only be about 2 ft high and only contain gravel and water to a height of 12 inches do I really need a footer for stability?

The last thing I need is for the whole thing to shift and fall apart down the road. Previous bogs have been made from old stock tanks so there was no issue.

Has anybody on the forum constructed a bog filter using cinder blocks and if so did you pour a concrete footer or simply build on bare earth or bed of gravel?

Appreciate the help.

Hey drjay. I had a similar bog for a number of years, no footer. In my bog, I made a 10x6 bog using 2 tiers of cinder blocks. I dug the ground down about 8 inches below grade inside the bog area, after laying the blocks. The cinder blocks were filled with dirt, compacted, and had rebar in them, pounded into the ground about 10 inches. I used the dirt dug from inside the bog and piled that up on the outside to help support the bricks. Put in a pond liner and underlayment, pvc pipe distribution system for the pond water, pea gravel and it held together for years just fine. However, I recently tore the entire thing out because it did not have a drain and that pea gravel filled up with gunk. If I did it over again, I would not use small gravel, and there would need to be a drain so the gunk could exit.

 

[hammer]

Railroad ties are impregnated with creosote and contain arsenic and various other controlled pollutants depending what state you're in, but we have to dispose of them as contaminated and regardless, I wouldn't use them on my property, they leach into the ground and it's not good.... to each their own though and this comes from somebody who had them used on multiple properties with sand, not a good idea.

My brother is in Tampa....
A footer would be best but you don't need it as long as the sand is 95% compacted which it should be at the depth you're excavating too naturally. 6-8" of stone could help if you have a drainage problem but the sand should take water as fast as you dump it on it.

In your case, the pressure of the water is the problem and I would not use cinder block, but you could use a cheap versa-lock retaining wall system with a smooth face on it, not split face. the interlocking nature is designed for retaining. CMU is famous for bulging and failing over time without meticulous construction and design/backfill.

hope that helps.

 

[drjay9051]

I briefly considered dimensional pressure treated lumber but went for the ties. These are quite old and there is little creosolte left. Dry and no odor.

Anyway I laid out the first course and they are very sturdy.

I will be staggering and tying together with 10 inch Timberloks

Yes they are about $2 each but way better than spikes, IMO.

Now to those you more knowledgeable ponders:

The final interior dimensions will be 14.5 x4 with a gravel bed of about 12-14 inches. Total height will come in at 21 inches. I will be sure to not trim liner so if needed I can alway raise
the bog. However with vertical cleanout pipes and periodic attention to heavy roots not an issue.

So the questions are as follows:
With a length of 14.5 feet do I space slits further away closer to pump to allow flow to distribute evenly towards the far end or will it all equilibrate on it's own?

Lastly:
A tee with 2 distribution pipes spaced app. 1.5 feet apart or just a single 2in PVC pipe straight down the middle?

Probably either would be fine but I tend to over think at times.

With my pond having a surface area of 280 sq. feet and my bog being 58 sq. ft I'm thinking 8 goldfish,plants and tadpoles will be quite happy

 

[GBBUDD]

I would run two pipes 2" a foot off the side on both sides leaving 2 feet in the middle but thats a foot from each pipe to the center

 

[drjay9051]

I would run two pipes 2" a foot off the side on both sides leaving 2 feet in the middle but thats a foot from each pipe to the center

Appreciate the input.

I just went out to look at the layout and 16x4 looks like a lap pool.

Maybe better to go say 8x6. Still would be more than enough for my size pond as I have no koi etc. From what I have read I should have say 10-15% surface area compared to pond as I have no heavy fish load. So that puts me at 28-40 sq. ft. A 6x8 gives me 48 sq. ft. Is more always better? Can you have too much bog filtration? This will be my only filter. Before I break out the timberloks I want to be sure.
I considered 8x8 but too hard to reach the center.

Your thoughts on sizing/shape.

 

[GBBUDD]

your growing every couple years by the sound of it Very common and well i would rather build a large bog for growth and bite the bullet once then to have to rebuild every thing a couple years from now and have to start over or build along side