Rectangular coolers do appear to be MUCH cheaper and then I can make my own manifold! How are coleman coolers or is there any brand or model that seems to perform better than another?
I've tried several different MLT setups. I've used SS braid and made manifolds from copper and pvc. The false bottom pictured below is the best setup I've used so far. It's also the most expensive. (surprise). But it works great and it won't ever wear out.
Everything is stainless, except for the outside metal washer. The threaded nipple is what goes through the cooler wall.
The o-rings are high temp (and thicker than they appear in the image). The larger washers compess the o-rings. I didn't have to modify my cooler, other than remove the plastic valve that was in it. This setup seals tightly. I don't have a problem with leaks. (You don't need the outer o-ring, but I use one anyway).
I use a plastic 90 degree elbow (pictured) to feed wort from the MLT valve to the BK. I have a gravity setup.
Not all the inside plumbing is shown. I have a stainless coupler that fits into the the female union. That connects to a short piece of silicone tubing. The silicone tubing attaches to the false bottom (pictured in lower right). I have small stainless tube clamps at each end. The tube doesn't come off, even if I stir the mash really vigorously.
I like that I can just unscrew the hose clamp on the fitting next to the MLT wall and remove the false bottom very easily. It only takes a second. This makes cleanup a cinch. When I'm done mashing I carry the cooler to a compost pile. I pour out the grain. I take out the false bottom. I wash everything up.
Cleanup is a breeze. It's fast and it's easy to get any and all reside out of the tun. Any reside is going to grow stuff. Even though the tun is before the boil, I still don't like to give bacteria even a speck where they can grow. I can quickly and easily get to every spot and clean it with just a rinse.
Another thing I like is that I don't get a lot of wasted wort with this system. Everything drains, and it drains fairly quickly. I've never had a stuck mash, at least not with this setup. I've had stuck mashes with other setups. I don't want to go through another one.
I don't have to vorlauf much. Usually a quart does it. After that the wort runs clean. First running or sparges, it's pretty much the same.
I use this same setup in my rectangular cooler, except that I use a round bazooka screen instead of the domed false bottom. I much prefer the false bottom. It might even work in my rectangular cooler. I just haven't tried it.
Lastly, if I ever do a mash that has a risk of getting stuck, I have a round nylon filter that I can put over the stainless dome bottom. The filter is the thing used on floor buffers. You can buy them at most hardware stores. They're a couple of bucks. I used one once. It was so hard to clean that I didn't use it again. If I make a beer with lots of rye or wheat, it's there if I need it. Again, I never want another stuck mash.
This isn't anything unique. I know a lot of people have the same setup. It works well for me.