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Vossy's Thermopot Mash Tun 1

This is a guide on 'how to' convert a thermo box into a mash tun. It is not the easiest way to convert one, but I wanted a bottom drain and no dead space. It was awkward, and took more time than I thought it would. Hopefully it may be of help to someone intending to do the same sort of thing. My thanks go out to Derek Spedding of the NCBA and the CBA's Brewers Contact, for pointing me in the right direction on this project.

Before starting the project I had to think about what I wanted from my mash tun. I was increasing brew length, so the mash tun had to be able to deal with 85ltr brew lengths of 5% beer. I wanted it to be bottom draining, and also wanted it to be insulated, so the mash temperature would remain fairly stable.

The bits

  • 80ltr Thermo Box £84.85 from Catering - Service - FR on e-bay here
  • ½" ball valve, part # 10397, £16.37
  • ½" brass nipple, part # 6576 £1.08
  • Both from http://www.bes.co.uk
  • 2 x ½" hole diameter stainless steel washers £0.90 from a local BSA parts shop (or from link below)
  • M22 washers form B from here http://www.a2stainless.co.uk
  • 1 x 15mm compression 90 deg elbow, £1, local plumbers merchants
  • 1 x ¾" flange nut £0.50, local plumbers merchants
  • 1 x compression coupler ½" female to 15mm compression £1.20, local plumbers merchants
  • 6 x M3 x 12mm button head bolts, 6 x M3 spring washers, 6 x M3 nuts, in stainless steel (already had)
  • JB Weld
  • Masking tape and pencil
  • False bottom 443mm circumference from http://www.hopandgrape.co.uk
  • M3 x 6mm button head bolts x 60, stainless (boltmeup, E-bay) £4.48
  • M3 spring washers x 100, stainless (Ultra Hardware, E-bay) £1.35
  • M3 Nuts x 50, stainless (E-bay) £1.94
  • Expanding foam and stainless sheet (already had)

Total cost £173.67 (not including consumables, labour and tools)


  • A drill
  • 20 and 40mm hole saw bits
  • 3mm HSS drill bit
  • angle grinder
  • dremmel
  • 15mm copper tube cutter
  • knife
  • tape measure.
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