The algae battle this year, of all the others, is a pain, and a never-ending cycle.
I could get a pre-done sand filter that would serve, maybe, but I’ve worked sand filters before, and they’re cranky: they use a levered valve for operate and backflush, and I recall the effect of a German Shepherd taking a bath in a pool and costing a filter gasket. The gasket for these things is a frail limp rubber device that looks like a wagon wheel, and it’s prone to problems.
Sand filters have their virtues, one of which is they clean relatively easily. I researched it and it turns out the heavy algae load of a koi point tends to make regular filter sand into a brick, with channels in it, and precious little filtering done. The answer is aquarium sand/gravel.
And I THINK I know how to DIY one that doesn’t backflush—you just dip out the sand/gravel and wash it, then reassemble.
The current plan: a flower pot. A big one. Or a garbage can. 3 bulkhead connectors, some elbows, some 1 1/2 inch hose for the inflow, and (for the bottom) a 2-inch hose. So…
Envision a square flowerpot. In the bottom, (a) 3-4 blocks of something to hold up (b)a sheet of eggcrate lighting grid. Atop it (c) a square of coarse filter. Atop that (d) a mass of sand/gravel, 50 lbs of it. Then (e) another square of filter. And (f) the inflow hose from a 2000 gph pump with a valve on the hose so I can adjust the flow.
Now, containing (a) is (1) the drain chamber, which has a 2″ bulkhead connector to a 2″ hose that will send *cleaned* water back to the pond.
Containing (b-f) is chamber (2), which is the filtration. It has no bulkhead nor drainage: it just drains down through (b) and (c) to (1.) Got it?
Containing (e) is chamber (3): this has 2 bulkhead connectors, and the first is the overflow drain, which will let any access of water flow out to the pond unfiltered, if it exceeds a certain level.
Finally, topmost in (3) is (f) the inflow hose from the pump (g).
This way, if the filter clogs and I don’t get to it in time, the thing will not overflow endlessly into the flowerbed, but will drain by the overflow drain back into the pond, until I get there to fix it.
Because it’s gravity-driven, the thing has to sit on the rim of the pond. A bit untidy, but if I find the right flowerpot or can, it’ll be at least ok-looking. And it won’t be there at all except when the algae’s out of control.
I want a square container if I can manage it, because bulkheads (a fancy twosided screw-in plumbing connector, in this instance) which lets you take a pipe through a wall and not have a leak) prefer flat surfaces. They have a flexible gasket, but they screw down tight and want a flat surface, which a square container can give.
Buying a proper pond-capable sand filter would cost about 1300.00 excluding the pump.
This one will come in under 100.00 and probably work as effectively, just not be as neat.
This may be worth a look. Some of these seem to include some of the components you’re mentioning.
http://www.lowes.com/Rain-Barrels/_/N-1z10uns/pl?selectedLocalStoreBeanArray=%5Bcom.lowes.commerce.storelocator.beans.LocatorStoreBean%4011df11df%5D&storeNumber=0172&URL=http%3A%2F%2Fwww.lowes.com%2FRain-Barrels%2F_%2FN-1z10uns%2Fpl%23!%26Va%3Dfalse%26page%3D1%26rpp%3D48&ipTrail=68.109.80.202#!
If that doesn’t work, Google Lowes Barrel
Aprpos the rain barrels, out back we have a molded plastic barrel that has a flat back to fit against the house. Sort fo D shaped, in top view. This would give you the surfaces for your bulkhead fittings. The rapid sand filters at the city water plant used three layers, coarse gravel at the bottom, sand in the middle, and powdered coal at the top. I think that was a function of the backwash, as the gravel would sink to the bottom faster than the sand, thus preventing the sand from escaping. Your piece of coarse filter takes care of that. The wikipedia article (to refresh my memory) talked about the size of sand, which may be relevant for you: “The space between sand particles is larger than the smallest suspended particles, so simple filtration is not enough. Most particles pass through surface layers but are trapped in pore spaces or adhere to sand particles. Effective filtration extends into the depth of the filter. This property of the filter is key to its operation: if the top layer of sand were to block all the particles, the filter would quickly clog.” You may already know that, but I didn’t, in spite of working for the city for 10 years. Hope this helps…
Did you see my comment about the flat-backed rain barrel? And the wikipedia article? I think my Firefox version 22 is not working properly. Usually I see my comments here right away…
No, I had that problem a few days ago myself. It’s the WordPress software.
I believe it just ate my response to yout comment about the variable transformer. Would a simple pot like what is used on a fan or light dimmer be sufficient?
OK, previewing seems to help. – We have a molded plastic rain barrel with a flat back, D shaped in top view. That would give you your flat surfaces for the bulkhead pipes. The wikipedia article about Water Purification talks briefly about fast sand filters, and the size of the sand particles to prevent top clogging. That’s the gist of my lost comment…
Mmm, must be having glitches. But thank you all. The rain barrels are a bit larger and a bit more than I’m hoping to have to go, but we’ll see how much 50# of sand turns out to need: has to be a stout container: wet sand is sort of like a 50+ pound rock.
IIRC one of the standard bags of “play sand” at HD is (pardon me, I think I have one in the breezeway), yes, 50#. One wouldn’t have much left over after filling a 5G bucket.
About the valve: I’d think with the valve anything but wide-open, which kinda isn’t its purpose, the pump will be running full speed, pushing against that constriction. I’m (innocently) thinking maybe a preferrable way to go would be an “autotransformer” that reduced the voltage to the pump, slowing it down and extending its lifespan.
Possibly this falls into the “duh” category…if you want to move around a container full of 50+ lbs. of wet sand, you either need wheels, or something that will fit on a hand truck or dolly. Type of wheel will depend on whether the route from its storage place to the location it will be when working is paved/graveled or not.
Sounds like a fun project!
As above, 50# of sand/gravel is the size of a bag of cement/play sand/what have you.
Add in the void space needed for the drain chamber and fill chamber, etc., and you probably end up with the volume of about one and a half 5 gallon buckets–7.5 gallons = 1 cubic foot, to 3 siggy dees.
Why move the thing when you’re not using it? The damn thing’s gonna be heavy! Just plumb it in with a cutout (bypass) circuit, not only for cleaning but for the non-algae season. The filter would be easy to hide: either make yourself a fiberglas fake rock or buy one, with a hinged back for access (or you could camouflage the entire filter as a pirate chest–all together now: “Arrrr!”–beside the waterfall).
I confess to being skeptical that this small a volume would be sufficiently effective a filter. I confess to further skepticism that this will gravity-drain fast enough, you need more surface area… gravel of a gauge large enough for fast drainage will not capture much algae IMO.
The more I think about it, the better the pirate chest sounds; you need the physical size, the flip top for access, flat sides for the plumbing, et bleedin’ cetera.
Thanks for the estimates. I was thinking 5 gallon bucket, too, for sand volume. The whole affair is not driven by the pump: the pump only lifts the water from the pond to the filter, and gravity sinks the water through the sand.
Yep, I know 50# of waterladen sand pretty well at least as far as weight: marine tank. It’s a heavy, heavy stuff. but when it comes to cleaning it, as I will have to do, a heavy duty scoop and small transfer bucket can cut the job down to size: it’s just slower. Dip it out, hose it down, dump it into a second bucket, repeat, hose out the chamber, then return the sand bit by bit…nasty job, but doable. And winter storage the same. Re size: ideally, for something like the size sand filter that allegedly works on a 5000 gallon pond, they say 24″ as a ball, with space at top and bottom; I may not have enough sand, indeed.
Re gravity draining that much sand, that’s why I want to valve the pump line, to cut down the flow from the pump until it matches the gravity drain rate, so there will be a settling area atop the sand, but so it won’t overtop the container.
I hope this coarse sand will work. If it won’t, I’ll have to go to finer sand, but that’s a bit more to get a scoop into when I have to clean it.
There’s one crazy fellow who jams what looks like a leafblower into his sandbed and blows, to roil it up for cleaning: I don’t think I’m that crazy. I engage in a hobby (marine tanks) that routinely puts water and electricity into a glass box, but a leaf blower??
“24 inches as a ball” for 5000 gallons –> volume of a sphere is 4 Pi times r cubed, all over three.
“Four thirds Pi are cubed”
“Pi are round”
“Oh shut up.”
😉
Here r = 1 foot and the resulting volume is 4.2 ft^3, or approximately 4.2 times the original estimated amount. This estimate does not allow for the voids at top and bottom –> call it 4 cubic feet and press on.
A larrrrrger pirate chest!
Backflushing seems ever so much simpler than cleaning the sand manually! Needs another bulkhead fitting up top, divert the crud-laden outflow into the garden or something (how far to the gutter?), all you’d need is two more valves than the original setup (and, of course, more pipe).
Schematic en route via email….
The volume of water was what was making me think big, too. But you’re only going to divert part of the 2000 gph I suppose. The density of dry sand/gravel is 1.6 to 1.8; wet it ends up as 2. So, the 50 lbs of whatever will net an added 15-25 lbs, considering the water displaced (the densities are from a pocket engineering guide, which I expect are pretty rough estimates). As an aquarist, you know about water weight, so doubling it should be a safe estimate; 5 gal should be roughly 80 lbs.
I had this idea: Put a vertical divider in a pot, with an arch in the bottom to let water through. Fill, say, the intake side with 12″ of gravel and the output side with 10″, with the outlet at about 11″. (Adjust height for more pressure.) If too much water comes in, it’ll just overtop the divider and go out the outlet unfiltered, but it will settle a bit. Everything is at the top for easy maintenance. Use multiple in parallel for more capacity.
Ideally, aquatic plants would use what the filters trap. Reeds? Water lilies? Native river plants? If they could be attractive enough, you could just put them by the pond, with no plumbing needed for the outlets. The plant roots would act as filters.
All this is a very theoretical, inexperienced thought, though. Still, remember undergravel filters? I don’t know if they’re still used, but I always found they worked well.
I came up with roughly the same estimate, just out of my head. As an upper limit, we know we have 50# of sand, then it’s wet, so if there were no sand in the bucket, then as they said in the days of the British Empire, “A pint’s a pound, the world around”, 8 pints/G, 8#/G, 40#/5G, so 90# tops. Subtract something for sand displacement. Couldn’t argue with 80#. 😉
The ability of fine gravel to trap particulate is pretty good (they’ve pretty well given up undergravel filters in fishkeeping, because there are biofilter methods that don’t pile up so much ‘stuff’. But the output of koi is amazing. The way horses (every stablekeeper swears) poop twice what they intake, koi double the burden of a given volume of water, so, for filtration purposes, my 5000 gallons have the dirt of 10000 under normal circumstances.
If the gravel turns out not to work, the play sand is an option.
We do have plants, lilies, pickerel, equisetum, but I swear, their ‘shed’ is almost as problematic as the koi’s contribution. They do uptake phosphate from farm-country and city water, and that helps: it’s fertilizer. And they’ll uptake contaminants like metals. But fish poo and slime-slough is a bit too much for just the plants, absent a gravel bed and that sort of thing, which we don’t have room for. Could do, but we’d have to move the water fall and splice the liner, which would be a really, really summerlong project we don’t have spare time for.
We will still have the particulate filter in the skimmer, which helps; but the finer stuff just gets right through, and multiplies by the hour in hot sun. This is where I’m hoping the sand filter will take up the slack.
How about using a large, rectangular kitty litter bucket to hold the sand? You can drill holes where needed, seal with silicon calk and spray paint the outside any color you like!
I guess I should have explained what I meant by an “autotransformer”. It’s a “variable transformer” with a dial and variable output. (Imagine two coils of wire, one slightly smaller than the other. Power one then as you slide the smaller inside the larger, the further in it goes the greater the induced current, the greater the output in the other coil.)
I used one to power some “dumb” fans in an old computer I made. I could dial them down when it was cool to reduce noise, twist it up when it was hot.
It sounds like the old transformer my brother’s electric train set used, with a simple pot to control the train speed. Jacob’s Ladders, anyone? Mad Science!
Ah, thank you, Paul.
Apologies if this appears twice–I just hit post and it did not appear. Anyway:
“24 inches as a ball” for 5k gallons –> volume of a sphere is 4 Pi times radius cubed, all over three.
“Four thirds Pi are cubed.”
“Pi are round!”
“Oh shut up.”
😉
Here r = 1 foot, resulting in a volume of 4.2 cubic feet. Allowing for void space at top and bottom, call it 4 cubic feet and press on ahead.
A larrrrrger pirate chest!
Seriously, CJ, backflushing is ever so much easier than hand-cleaning all that wet sand! All you need is one more bulkhead fitting and two more valves to plumb it (schematic en route via email)–and, of course, more pipe. Route the crud-laden water to the garden (how far to the gutter?).
Garden will be immediately below it. And plants love fish poo. Hmm. Interesting. A lot of valves, but no reason why that shouldn’t work.
If you go with the backwash idea, I should repeat what got left out yesterday. In the city water plant I worked at, the filters had three layers: coarse gravel on the bottom, sand in the middle, and powdered coal on top. You don’t need the coal, it soaks up random organics, the gravel makes the bed for the sand, and prevents the sand from geting out the bottom. Being heavier than the sand, it sinks faster after the backwash, and covers the drain holes. Then the sand, and finally the coal settles on top. I’ll have to try to recreate a sketch of the fast sand filters with all the backwash plumbing included. And backwashing can be tricky, too much flow will carry the sand along with the gunk out the backwash drain. That’s the beauty of centrifugal pumps; they don’t mind being throttled. Might be inefficient, but they don’t break. I’d love to go back for a tour of the place I used to work, I’d get lots of pictures, and maybe a video of backwashing a filter.
It occurs to me that if you run the water through a jelly bag or a coarsely woven pillowcase first, (on really filthy fist runs), not only will the sand filter need less cleaning, but you will also get some really good compostables…
A 20-inch pot should be more than big enough to hold all this.
I wonder if one of those drip-irrigation system anti-siphon valves might work? IIRC, they have standard garden hose threads on them, though I can’t remember if they’re male or female. They’re required on the drip-irrigation systems so that moldy water from the hoses doesn’t get siphoned up into the water supply in the house in case the faucet is left open.