This is the unit I fabricated from 4 inch PVC pipe. Note the flange at the bottom to make it air-tight and able to stand up. Also notice I've drilled and tapped a hole for a 1/4 inch NPT fitting for a hose connection to vent out the hydrogen/oxygen (top left). I've already tested this plate design in a large empty pickle jar and know it will work great. The fact that in this PVC unit I can't watch the bubbles form won't matter as long as the gas exits the unit in sufficient quantity. If you make your unit from plexiglass you will be able to watch it work better. But in time that plexiglass will probably become very discolored anyway, so I would think the extra expense not worthwhile.

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