Backyard Aquaponics
A place to discuss aquaponics

Thanks! I've been puzzling over the simplest way to prevent leaks between the liner and the PVC pipe that I'm going to run through the end (and attach to a drainage pipe running the length of the bed. My latest thought was to just make a hole through the plastic liner and gather an inch or so around the pipe and secure it with a stainless hose clamp. Anyone think that is crazy?

that may work, but im sure you will get wrinkles in that gathering.... or the gathering will ruin the folding / smothness in other areas of the bed.

try to find a bulkhead like this:
https://www.bunnings.com.au/holman-50mm ... g_p4813626


i didnt use such a thing because they are very expensive in the larger sizes.

i forget how mine was exactly, but i have glued the liner to the wood, then cut a hole slightly smaller than the pipe, then forced pipe through which wedged liner between pipe and wood, then added another fitting which can fit a 90mm pipe inside, but has a flat lip around it and glued again or similar.

What size pipe are you going to use? The way I put mine through was to get a threaded nipple of galvanized pipe just long enough to stick through both sides of the wood and thread into another fitting, get 2 threaded pvc to galvanize fittings, plenty of thread sealer, and screw the pvc fittings onto both ends of the nipple tight against the wood and plastic liner. Might have to cut a thin spacer if the fittings don't tighten down against the wood and liner. If you do, mount the spacer on the outside of the box. Also look at the pvc fitting. Should be information about the fitting made onto the edge. This should be sanded smooth on the fitting you intend to use on the inside to get a good seal against the liner.

Thanks guys. Yavinaya, I started thinking the same thing about getting folds in the liner that would eventually leak. That fitting you linked to is a beautiful thing but hard to find and really expensive here in Costa Rica too.

Aufin, that sounds like a good method but I want to avoid any metal and it also doesn't leave much room for sealing against the liner, if I am reading your description correctly but I guess with sufficient sealant, it would be fine. It is a rather elegant solution. I was aiming for 3" (75mm?) pipe. I think I'll look again at something like a toilet flange. If I could just find one that had a good fitting on either side... The regular flanges have that unhelpful sloping part on the side where the toilet would normally go. Most inconvenient.

Aufin, my system is similar in size to yours. Based on your experience, what would be the minimal size you could get away with for the exit pipe out of the bed? I imagine having a bigger drain pipe within the bed is helpful in terms of drawing water through, but at the exit, could you get away with 2"? Looks like you come out of the system with 4" and go down to 2". I'm wondering about making that reduction inside the bed, so that the exit fittings can be smaller.

The large bed is 4 inch. I reduced to 2 inch after exiting because the fittings raised everything off the floor of the box leaving too much water inside between cycles than I was happy about. I think 4 inch is more than necessary. My smaller beds are drained with 2 inch.

The small amount of metal shouldn't be enough to worry about.

The pvc/galvanize fittings seal very nice. You don't need as much surface area as one might think to make a good seal. Plus, there aren't many glues that stick to plastic sheet. The method I used is a solid connection and has withstood many stumbles without leaking. The more sturdy you can make your connection through the wood the better off you'll be in the long run. Going back and disturbing everything to fix something that could have been avoided is not my idea of fun. Expect your plumbing to take a bit of punishment as you work around your boxes. The more you can stabilize the better off you'll be.

Thanks Aufin, makes sense. I think you are right about the metal too as galvanized pipe is really just steel coated in zinc. The amount of zinc released from such a small connection would be negligible.

And what's this about "work around the boxes"? I thought I read somewhere about sipping coffee, tossing some fish food, and breaking out a cold one as the sun goes down? :-)

dont underestimate zinc.
depends what fish you do of course, goldfish will handle almost anything, that piece of pipe could build up with enough zinc to kill your trout though.

then there is the fact zinc will wear off and the rust will start - in AP water this will happen VERY fast.

take it from someone who *frack* up when a newbie and used galvanised tanks, zinc is to be avoided when it is saturated or there are multiple passes.

there are PVC stormwater fittings which can be screwed together like that bulkhead i posted if you look hard enough at your local hardware/plumbing store.

I guarantee the first bed would have higher nutrients. Do you see a filter in his sketchup? NO! That means all solids are being trapped in the sand. Yes the dissolved organics might pass through the sand, but the solids are NOT going to pass through the sand. That means you are providing a higher nutrient level to the sand bed in the form of solid fertilizer than you would be providing to the other bed in the form of liquid fertilizer. It will not take long for a sand bed to become disgustingly full of rotten solids which to some extent the plants would probably love, therefore it would be a failed attempt if you were trying to compare apples to apples to see what method is actually better in a scientific study. On a hobbyist level it probably doesn't matter, but if you have read the iavs website and the claims they make they are making some pretty bold claims about how much better it is to run a sand bed than other typical aquaponic systems... so all I was suggesting was if the OP was going to try running two side by side as a comparison it should be more scientific to try and provide the same nutrients be it solid or dissolved to both systems.

Sometimes ya just want to walk around every thing just to make sure. Other times ya gotta look busy to stay outta trouble. Course, there's that one little weed that doesn't belong.

Back from an awesome four day aquaponics workshop hosted by SchoolGrown (schoolgrown.org). Learned a ton of tips and tricks and am excited to be back on my project! Jon Parr of SchoolGrown put me onto Uniseals as an alternative to (typically expensive) bulkhead fittings so I brought a bunch back and used my first one on the grow bed drain.

Hoping it will hold a seal even with my less than ideal "liner". Getting the Uniseal in was less than fun. I've read a bunch of different ways to do it (tapering end of the PVC, cutting slits in the PVC, and applying soap). I did all three of these things (see photos) but still failed to get the pipe through. In part, it was because of the awkward angle I was working at. Anyway, I eventually soaked the uniseal in boiling water for a couple of minutes and that did the trick. Next time I'll just sand the end of the pipe and heat up the uniseal!

Since my prototype system is only about 8 feet long, I decided that the central drainage pipe is probably overkill so instead I created a horizontal drain at the end out of some 2" PVC with slits down almost to the bottom. I'll cover this with some nylon mosquito netting before I add the sand.

Wow! That sounds like a great trip! Where are the pics so we can live the workshop vicariously through you?!

You've got no choice but to hit the ground running after an experience like that!

I almost got some Uniseals on my last trip up to the States, but I didn't get them ordered ahead of time and didn't have time to do it in the little time I was up there. However if you find you need more, or other things from the land of Amazon honey, I've been having great experiences using Box Correos as a package/freight forwarded for Amazon purchases. In the past 2 months I'm 3 for 3 on... Amazon ships to address in Miami, package is forwarded to Costa Rica, passed through customs, and the package arrives at my nearest post office (~25km down the volcano) in less than a week from the time my packages arrived at the Miami warehouse. Each time I had regular progress updates and I knew fairly close to what all of my costs were going to be up front. I'm considering shipping quality pond liner like that. Americover has 20 mil reinforced white Dura Skrim, food safe with UV protection, 6' x 50' for $108 USD. That's enough nice pond liner for 1m x 14m x 30cm -- it weighs about 14 kilos: Americover - 20 mil Reinforced White R20WW by Dura Skrim


That looks like a great start you've got going. Plus if later you decide to do 1 or 2 center drains, you could add on to what you've got to make an inverted T drain. Glad you're back and obviously got your tools out of customs!

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Sam

Hey Sam,

Yes, I have no excuses now! I think I also found another source for sand (polvo de piedra) that will do. It's inert but slightly on the larger size. Relatively free of clay and silt though so I think I'll give it a try. I only need a bit less than a cubic meter for my trial system anyway.

The picture below is from the SchoolGrown greenhouse at the Felton High School. Really nice setup and it features Jon Parr's amazing Cleverponics rafts. He ingeniously made the holes tapered to match his starter plugs so that the seedlings can be placed directly into the rafts without any net pot or other container. Pretty efficient system!

Great news about shipping. We are going to try the same thing here in Heredia. Looks like a great price for the 50' of Dura Skrim. Everyone was also talking about Ultra Skrim (http://greenphoenixfarms.com/ultra-scrim-now-available/) - thinner, just as tough, and truly food safe. I guess Dura Skrim is apparently not - at least according to that article and from the manufacturer of Ultra Skrim (http://www.globalplasticsheeting.com/aq ... astic-film).

More pics soon!

More progress! Completed the rain shield over my grow bed. We get some heavy rain showers here in Costa Rica, especially this time of year so this will be good protection for the plants.

I should note that the arrangement of my tank and grow bed have a lot to do with the property that we are currently renting. The bank along the wall (which gets a lot of sun) was handy to support one side of the bed but next time I'll keep the grow bed on the ground, or at least much lower. For iAVs where much of the growth will be larger plants, I figure having it so high is going to be kind of inconvenient. Anyway, it's a prototype!

That looks great! I like your "zin' transparente"!

I've got a corner of the backyard I'm claiming as aquaponics zone that kind of looks like yours. My plans are to entirely cover that area with transparent tin and and route the run-off into a rain catchment system. However, I've got some I've used in our cuarto pila (back porch laundry room) and a 2nd sala probably 5 or 6 years ago that has changed from totally transparent to opaque and less flexible (not quite brittle.) I think next time I'll have to special order some good stuff with UV protection, etc. What I got locally was kind of crappy.

Your system is really coming together!

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Sam