I started it last night with an 18 gal tub I had emptied, and today I got two more tubs, to make more. Of course they don't sell the same brands, sizes, and all that that would have made it easy, since I saved the molds! That's what takes the longest - making a mold (I use some heavy cardboard), to fit the shape of the tub, to use to cut the lid, for the shelf. I got most of it done last night, and waited for the glue to cure, to finish today.

I finished that SIP today - it will be easy to do again, as that initial mold for the shelf is what takes the most time. I also had a bunch of PVC drain pipe scraps I got from a friend, and cut 5 pieces for this SIP, plus 17 more, so that part is done for more!
Shelf for the new sub-irrigated planter, cut from the lid. by pepperhead212, on Flickr

Gluing an end cap on one of the wicking chambers, clamping it in a bench vise. by pepperhead212, on Flickr

Finished shelf, with the two wicking chambers capped off and installed. by pepperhead212, on Flickr

Shelf of the SIP, shown from underneath. by pepperhead212, on Flickr

I haven't been at this for too long, and I didn't have the advantage of being able to join the other forum...what is a SIP?

Speaking of that, is there an acronym thread here?

SIP is just short for a sub-irrigated planter. Earthboxes are the best known commercial brand, this is just a much cheaper way to make some - I have I think 9 Earthboxes, but many more homemade ones, of the large tubs, smaller tubs, and buckets inside larger buckets. The "wicking chambers" sit down in the water section, below the shelf, wicking the water up to the soil mix, but it does not sit in the water, so the mix stays aerated.

As I said, once the form is made for marking that lid, to cut the shelf, it is much faster to make them. I got 2 more almost made, in about 2½ hrs, in my workshop. It helps to have a good workshop, for all the cutting and drilling! I didn't finish because the caps I need for those wicking chambers I had to order - not available locally.
Two more SIPs finished, up to putting on the wicking chambers. Had to order some things. by pepperhead212, on Flickr

Looks good.
Questions!
What brand, how much for the bins? How deep is your mix? How heavy? Do you leave them outside? Empty or full of mix over winter? Do you grow root crops in them? Do you cut holes in the sides of the plastic tub for air?
My rain gutter buckets were tree nursery buckets. Left outside, they are still together after...5 years? 5 gal plastic buckets would be cracking by now.

@JRinPA Those tubs are cheap ones I got at Ollies - $5.49 each, though I saw them in the most recent add for a dollar more, which still isn't bad! The plastic seems like the type that some of my oldest ones are, though it's hard to tell exactly what they are. Some of the buckets I have (I have 4 gal inside 5 gal, and 5 gal inside 6 gal buckets, for SIPs) are over 7 years old, while others start cracking much sooner - just slightly different plastics.

The mix in these will only be about 8" deep, but there will be a large hump in the soil, so about 12-13 gallons of soil, I'm guessing, but this is the first time with this brand - DiamondPlastics. I've used a bunch of brands - whatever was on sale! Some, like the buckets, are obviously different plastics, and I have 2 this year that may be replaced with these - they are cracking on the tops badly, but still ok underneath. I'm thinking it's more uv light on the tops?

Once filled, and soaked, and filled with water underneath, these things really can't be moved! This is the way I can tell if the drip emitter isn't working in one (besides a plant wilting!) - just lift the edge. If it doesn't want to be lifted, it's working!

I've never grown root crops in these, though I've read that it can be done. Tomatoes, tomatillos, eggplants, peppers, cucumbers, bottle gourds, bitter melons, okra, and sometimes some greens, though I usually don't do cold weather crops, as I have to get the water out, and cover them, before it freezes. I do this simply by tilting them over (not really that simple!), and letting the water drain out of the drain holes. The buckets I lift the small one out, and dump the water. Then let it drain a few more days (hopefully, no rain!), and eventually, all these things get grouped together, and covered with tarps, weighted down. The next season, I remove some of the mix (I usually just dump it in raised beds), and replace it with fresh, and some fresh fertilizer, mixed with the soil mix, if organic, or added to the "sock", as I call it, if inorganic, and add some dolomite, for the tomatoes.

I drill some holes in the corners of the containers, just under the level of the shelf - this way, any way the SIP is tilted, the water will drain, and not build up in the mix.
One of the 4 holes in the corner of the SIP, for drainage. by pepperhead212, on Flickr

Awesome, thanks!

So you just use overfill/drainage holes but no holes up further in the sides for air exchange. So it does not have to be lined with landscape fabric on the sides. I was not sure about that.

I do think the UV is what kills plastic. I've read you should paint it to help that out, but I rarely do it.

The problem is that polypropylene plastic - the semi-flexible type that is best for this - does not take paint well. I did paint some of the buckets - not sure if it helped.

The original Earthboxes did not have any holes in the side, just that one of drain hole in the middle of one of the sides, so I figured more holes were not necessary. I do put a layer of shade screen on the bottoms, and on the sides of those wicking chambers, to keep the peat in, as much as possible.

I use old window screen cut up to fit the bottom my buckets. I wet pack the wick with extra perlite, and really stuff it tight, but don't wrap it in a cloth. I suppose I lose some into the reservoir, but not that much, and the holes are probably 1/2". Sometimes the roots do reach all the way down to the screen or maybe through. I don't know if they are "supposed" too, but it seems to work well enough. I just wonder how carrots or sweet potatoes would work on it. Red beets...I've found they do better in the ground. Or least, make a better use of space. I think maybe they get too hot.

I always add extra perlite, to the wicking columns as well as the mix. And pack it tight, as well. I have used just plain screen, when I was out of the shade screen, but I got another roll of it, before a local hardware store closed for good a few years ago. Have hardly used any since then, but this year I have the 3 new ones, plus two of the first Earthboxes I got, that I finally emptied (after 7 years, I think), and I was amazed at how little sediment was in them!