edited December 2013 in Usage

when I run my reflux still, I notice the boiler gets hard. I assume there is some pressure there but I have no idea how much and there is no pressure relief valve on this system. This is an area I'm a bit vague on and I dont see it discussed often.

Is the dephlegmator creating a great deal of pressure or are the pressures minimal assuming the vapor path is clear of physical obstructions?


  • What type of packing or plates are you running? I have a pressure gauge on my boiler and the needle does not move. Total pressure should be less that 2psi. If you don't have a pressure gauge I would suggest you add on for safety. If you get some sort of blockage your still could be pressurized and blow up. With a gauge you would be able to see there is a problem and kill the power.

  • running perf plates. all mash is pretty clear as I use no grains or solids.

  • How many plates? What diameter column? What is the open % drilled surface area of each plate? What size are the holes drilled to?

  • 4 plates on a 4" column. with a 1/2" downcomer plus ~85ea 5/32" holes, I'd guess about 20%-30% of the plate is open.

  • You can generalise the pressures involved by adding up the total depth of liquid held on all the plates, as you are running perforated plates. There will be some but not a lot.
    The previous comment about a PSV for a blockage in the column is a good point though. The pressure relief is only likely to be needed when something goes wrong. If you don't have it then the consequences could be a lot worse.

  • I hear about a simple and cheap manometer but does anyone have a working example that we could emulate? A water filled clear hose that holds back the normal pressure but vents to the outside world in the worst case scenario?

  • Fiji, for most 4" columns 3/4" downcomers are suggested and an open plate area in the 8 to 10% range...

    You may want to check your hole diameters and number of holes per plate to verify the open area...

    take care, have fun, be safe,


  • Some folks just connect a hose to the boiler vapour space, and put the end in a bucket of cold water. Depth of water in the bucket equates to the blow off pressure. It also helps condense the vapour.

    If you do distil with grain/corn in the boiler, and use a large diameter hose, this is one way to deal with the solids that might block a normal (small bore) Pressure Safety Valve.

    On big stills that distil on the grain, they have a (big) bursting disk somewhere, just in case.

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