It is worth mentioning that there is considerable resistance to the flow of water through a 16 ft length of 3/i6" tubing and you may find that friction alone will be insufficient to hold in place the plastic tubing leading from the water supply in the house. There is nothing worse than having the water line blow off in your absence and finding your workshop flooded when you return. So play it safe. One neat solution to this problem is to use the metal fitting and 1/4" o.d. high-density polyethylene tubing used for connecting a humidifier to the house water supply line.. These little kits are inexpensive ($12-ish) and come with 25 ft of high-pressure polyethylene tubing, a length which is convenient when the water supply is not adjacent to the still. The drain from the cooling coil involves no pressure so any type of tubing will do.
If you smell alcohol fumes as soon as distillation starts it means that there is insufficient cooling. Test the cooling water leaving the condenser and, if it is warm, you should increase the flow-rate. If it is cool then there is no point in increasing the flow of cooling water because the problem is insufficient cooling surface. This is unlikely to be the case if you are using a 750 watt heater in the boiler because the cooling coil as described can easily handle this amount of heat input, but with a higher wattage heater you should not take it for granted. If you find you need more cooling surface then you'll be forced to use a longer length of 3/16" copper tubing. 16 ft is only just sufficient for a 750 watt heater so you might wish to consider going to 18 ft at the outset.
The volume of water you are likely to be using during the course of a distillation is discussed in Appendix IV. If water is a problem you could experiment with air cooling, circulating the cooling water through an automobile radiator with a fan blowing air through it.
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