How to build a cool box mash tun

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HisDudeness

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First off this isn't the cheapest possible way to build a mash tun and it wasn't intended to be. There are also different methods for doing this that I may or may not mention in the post. I have tried to aim for something that will hopefully be durable and perform well while still being significantly cheaper than most of the commercial offerings.

This design uses a thermos 28L coolbox, ball valve tap and 15mm copper manifold to filter the wort. I based it on a video on youtube with a few extra tweaks that I hope will improve it. This should be enough volume for most 23L batches with a grain bill around 5kg total.

Here are the required parts:

Coolbox (28L Thermos is 19.99 on Amazon you can certainly get cheaper coolboxes but I chose this on the basis of strong reviews for insulating properties)
Ball Valve Tap 1/2BSP £4
Tank Connector 1/2 BSP £4
1m * 15mm Copper Pipe £7.60
3 15mm Copper Tees £3
4 15mm Copper Elbows £2
Short piece of reinforced hose (free, chopped it off the garden hose)
B&Q quick hose connector (socket) £1
Brass 1/2BSP to quick hose connector (plug) £3
Jubilee Clip £1

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HisDudeness

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First take your tank connector and use it to mark the centre of the hole you will drill through the wall of the coolbox, this should be as low in the box as you can get it.

It is possible to fit a tap straight through the box but I used a plastic tank connector to hopefully make it a bit more structurally sound and maintain the insulating properties as much as possible.

Drill the hole out with a 20mm spade bit and fit the tank connector and tap assembly.

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HisDudeness

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To construct the manifold I used 15mm copper pipe and cut it up as follows (get a pipe cutter for this part).

2 * 140mm
4 * 100mm
2 * 64mm
1 * 50mm

Then cut slits into the pipes on 1 side (this is pretty tedious you could also drill small holes)

If you put a small dent into the elbows and tees on the edge then you can get them to fit together pretty securely without having to solder.

Fit the parts together and test fit in the tun. (Slits on underside of manifold)

I used the hose quick connectors here so the manifold can be easily removed for cleaning. The hose connector is interfaced with the manifold using a short piece of reinforced hose and a jubilee clip attached to the 50mm piece of copper pipe that connects to the centre Tee.

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HisDudeness

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The tun is basically finished now so fill it up with some water to check for leaks and make sure the tap flows properly. Drain the tun fully and measure any remaining water, this is the tuns deadspace and will be important for calculating water volumes for mashing/sparging. This tun leaves just under a litre at the end, this could be better but the plastic in the bottom of the box domes up slightly which stops the filter sitting as flat as it could.

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HisDudeness

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I have seen several people mention the lids as a weak point in the insulation of coolboxes, so to pre-empt this I used some polystyrene and cut out a plug to fit the top of the box under the lid. Cut the styrene sheet to size and then wrap in foil followed by clingfilm. I fashioned a handle from gaffa. The fit is quite snug and should help keep the heat in.

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HisDudeness

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And thats it, once I have actually used it properly I will let you know how it performs! Hopefully this will be helpful for others looking to build a mash tun :thumb:
 
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stevej

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Cheers Steve, trying to give a little back after all the help and information I have gleaned myself from the forum :)
Wish you had done this thread a few weeks ago before i made mine :lol::lol:

Its a great thread very easy to follow and nice pics!:thumb:
 

TheRedDarren

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Yea, spot on mate, nice one!

Can I just voice a concern though...
You've made that handle out of gaffatape, that's actually inside the tun. That stuff has some nasty chemicals in it. It may well leach them..?
 

HisDudeness

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Yea, spot on mate, nice one!

Can I just voice a concern though...
You've made that handle out of gaffatape, that's actually inside the tun. That stuff has some nasty chemicals in it. It may well leach them..?
I hear what you're saying, its not ideal but the tape is only on the top side of the plug and it seals pretty well, so on the water test there wasn't any build up of steam/condensation on that side that could leach the nasties back in (hopefully). Having said that I will probably try and sort out a better solution when I can....
 

TheRedDarren

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I hear what you're saying, its not ideal but the tape is only on the top side of the plug and it seals pretty well, so on the water test there wasn't any build up of steam/condensation on that side that could leach the nasties back in (hopefully). Having said that I will probably try and sort out a better solution when I can....
Ok that's good to know. I'll also do this with mine I think. Where did you get the polystyrene?
 

keat64

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Have you performed any temperature tests ?.
I got a cooler today and it's insulation properties are pretty poor.
 

ManseMasher

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They pretty much always are. If you take it apart you will most likely find a sheet of 5mm polystyrene. Crap insulation. But they are meant to keep things cool, not hot. Wrap it in a duvet, a sleeping bag, a hot water jacket, cut up a camping mat etc. etc. Whatever you choose, insulate the life out of it and you won't go wrong.
 

keat64

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I removed the 3mm polystyrene and replaced it with 6-8mm foam underlay.
And since then wrapped over the foam with aluminium foil.
Gonna test again tomorrow.
 
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