I decided I needed a bigger mash tun. The 5 gallon round cooler I have been using for years just didn’t allow enough freeboard for brewing bigger beers, like the Brooklyn Brewery Black Chocolate Stout I made last October. I thought I would never get the sparge to run to completion on that one, and there was a lot of frustration involved in brew day because of it. BTW – the beer turned out fantastic – it will be my entry in the AHA competition this year if I don’t drink it all first.
So back on the ranch, I decided to double my capacity to a 10 gallon round cooler. It provides more than enough headroom for my 5 gallon brew day, even for big beers. Even super big beers. But I needed a replacement for the false bottom I have been using on my 5 gallon model. Because I am reluctant to spend money on things I think I can make myself, I decided to make my own.
Reflecting on some reading I have done on homemade mash tuns using rectangular coolers with copper pipe strainers, I figured the copper pipe concept would be adaptable to a round cooler as well. Using 1/2 inch copper pipe, tees, and elbows I made a three legged device that slipped inside of the 13 inch diameter cooler. I used an electric grinder with a thin cut off blade to make slices in the pipe at 3/8 inch intervals. I was careful to not cut too deep so as to weaken the pipe significantly and cause it to bend under the weight of a huge mash bill. I did minimal filing and cleanup to remove copper burrs.
I used the bung from my old unit to replace the plastic cooler valve, and pushed my hose through it into the waiting open tee inlet on the new copper header. The ID of the bung is slightly smaller than the OD of the hose, so it makes a good seal and didn’t leak a single drop of wort. The hose slipped into the copper tee with a wee bit of clearance but I figured what the hey, that’s just like cutting another slot in the copper pipe. I slipped some thick washers over the copper pipe to hold the device about 1/2 inch off of the cooler bottom. You can see in the picture that I actually introduced my mash water directly from the boil kettle through the device into the BOTTOM of the mash. No guessing on when I had enough mash water!
All of the parts (8 pipes, 4 elbows, and 3 tees) slip together and are easily disassembled for cleaning, drying and storage.
The device worked great! I was concerned that I might not get enough flow out of the slots I cut (I actually did calculate the total flow area) but I ended up having to restrict the flow from the hose in order to sparge at a reasonably slow flow rate. You can see from the photo that there was plenty of headroom after mashing with this 12 pound grain bill. I need to adjust my calculations on strike water temperature a bit to allow for the different heat transfer properties of the larger cooler.
By the way, the beer I made was Bell’s Two Hearted Ale, one of my favorite IPAs. I’m thinking of using it for Brett bait. I brewed it on January 29, 2011, which would have been my grandma’s 100th birthday had she still been alive. I’m going to have to come up with a catchy name for it to commemorate that special event. The original gravity came in at 1.062, and I just measured a 1.014, so I’m looking at a 6.5 percenter or better. The bitterness and the flavor of the 100 percent Centennial hops was excellent! I’m going to let the beer rest on the cold yeast (56 degrees right now and I’m trying to keep it warmer in our current cold spell) for another week to assure minimal diacetyl, then I’ll rack to secondary and dry hop and let it condition cold for a couple of months.
Until next brew day (which probably won’t be until April due to a heavy day job work load), Cheers!
This is my Centennial. You'll note that it is smaller than the Cascade; last year it didn't produce any cones. I'm hopeful that it will produce in its 2nd year. Can you spot the homebrew? Hint: Its a freshly tapped Two Hearted Ale made with 100% Centennial hops. Someone on the west coast who drives a VW should be drooling... 
Then, when I went to get a refill, I came back and the neighbors were in my boat.