I am SO annoyed, I was going to get pictures all along so I could post them all, but DH got the pool done before I could get the camera out! It was a super fast & easy "conversion" and I highly recommend. I bought a used Little Tikes pool from Craigslist for $20, like this one:
It's about 5 1/2' across on the top, and a bit over 12" high. There is a "deck" molded in on the top with wood grain for texture, and a step on either side, as well as a slide (would be hilarious if they used the slide, but so far, nada). There is also a drain plug.
DH removed the drain plug and fitted a brass plumbing part called a - no, I did not make this up - urinal spud. It's for use with thin-walled applications such as this. He put some of that white plumber's putty around the edges to be sure it sealed. On the back side, it is threaded, and DH put a fitting to accept a section of hose onto that. Then, we sacrificed an old hose and cut it to about 6' long - long enough to run it OUT of the duck pen, which is what I was wanting. (Before, I was dumping the pool every other day right into the run, as it had no drain plug & was too large to drag out the door of the run.) On the end of the hose, DH put another fitting and an "end cap" so that all I need to do is remove the end cap, and all the icky water will drain out. I've not emptied it yet, but will do so tomorrow. Since the plug is about 1" up from the bottom, I suppose I'll have to add a bit of water at the end of the draining & swish it around & maybe tilt the pool up to get all the crud from the very bottom - hope that works.
Anyway, I just wanted to throw this out there & mention the oddly named part - it could be used on any toddler-type pool with a thicker plastic, or even a sandbox. The ones meant to actually be a pool, though, are a bit taller. My ducks can actually dive down & swim under water in this, which they could not do with Tommy the Turtle sandbox we had before this. It's a blast!

It's about 5 1/2' across on the top, and a bit over 12" high. There is a "deck" molded in on the top with wood grain for texture, and a step on either side, as well as a slide (would be hilarious if they used the slide, but so far, nada). There is also a drain plug.
DH removed the drain plug and fitted a brass plumbing part called a - no, I did not make this up - urinal spud. It's for use with thin-walled applications such as this. He put some of that white plumber's putty around the edges to be sure it sealed. On the back side, it is threaded, and DH put a fitting to accept a section of hose onto that. Then, we sacrificed an old hose and cut it to about 6' long - long enough to run it OUT of the duck pen, which is what I was wanting. (Before, I was dumping the pool every other day right into the run, as it had no drain plug & was too large to drag out the door of the run.) On the end of the hose, DH put another fitting and an "end cap" so that all I need to do is remove the end cap, and all the icky water will drain out. I've not emptied it yet, but will do so tomorrow. Since the plug is about 1" up from the bottom, I suppose I'll have to add a bit of water at the end of the draining & swish it around & maybe tilt the pool up to get all the crud from the very bottom - hope that works.
Anyway, I just wanted to throw this out there & mention the oddly named part - it could be used on any toddler-type pool with a thicker plastic, or even a sandbox. The ones meant to actually be a pool, though, are a bit taller. My ducks can actually dive down & swim under water in this, which they could not do with Tommy the Turtle sandbox we had before this. It's a blast!