Finally, I got round to making my own mash tun this weekend. Since Fendog took most of our all-grain set-up back to the farm, I have had to make do with extract and partial mash brews. But I just managed to get a cheap cool box from eBay for £10, so this weekend I converted it into a mash tun. It was much easier and took less time than I expected, so I thought I would post some full instructions here so you can all join in the all-grain fun.
Basically, all you need are three things (plus a couple of cable ties to hold them together):
1) A coolbox – The bigger the better, but at least 24 litres. You can easily pick these up secondhand on eBay, or the cheapest new ones I can find are £19.99 from Amazon
2) Flexible stainless steel hose with 3/4″ BSP connector – £1.79 from Screwfix
3) Drum Tap with 3/4″ BSP thread – widely available, e.g. £3.95 from Dorset Homebrew (you can get them cheaper elsewhere, but make sure the thread is long enough)
Step 1: Attach tap to cooler
Use a hole saw to cut a hole for the tap. It needs to be just big enough to fit the thread through, so that a tight seal can be made with the back nut. You want to position the whole so that it is as close to the bottom of the inside of the coolbox. But make sure its not so low that the back nut will not fit, or the bottom of the tap is off the floor.
If you have kind of cool box (like the one I used) which has an inner and outer casing with polystyrene insulation in between, then you will have to cut a slightly larger hole in the outer case and polystyrene, so that you can pass the tap through it and fix it tight to the inner layer of plastic.
Step 2: Make the strainer
Using some cutters or a hacksaw, cut the end connectors of the flexible hose. You will see that the hose is made of a stainless steel braided casing around a rubber tube. You need to PUSH (not pull) the steel braid off the rubber tube. If you pull it, it will only tighten, but if you push the ends of the braid towards the centre it will expand and allow you to slide it off the rubber tube.
One of the end pieces that you removed should be a compression fitting with a outer nut and an “olive” or compression ring inside. The other end should be a simple 3/4″ BSP nut with a (possibly detachable) hose barb on it (Piece A in the picture above). This is the end you want. Use cutters or a hacksaw to remove the end bit of the rubber tube and braid.
Cut a small section of the rubber hose just big enough to over the hose barb on piece A. Then slide the braid onto it. You can fix this with a hose clamp (I had one lying around) or simply with a cable tie.
The other end of the braid can also be pinched together with a cable tie, and you should trim off any sharp bits with a pair of scissors.
Viola! You’ve got your strainer. If you got the right size hose in the first place, this should screw on to the thread of the drum tap inside the coolbox.
And then you are done, my friend. You’ve made a mash tun. How easy was that?
Can’t wait to try mine out next weekend.