The finished electrolyzer. The two PVC end plates are clamped together with 70mm long M8 stainless steel bolts with Nyloc nuts. After initial tightening the electrolyzer was submerged in hot tap water (about 60 C) with the gas vent valves closed. This softened the PVC gaskets and allowed the stack to be tightened up even further to provide an excellent seal. Note that the 12mm PVC plates are quite soft and some bulging is visible. Two additional bolts would have been useful to equalize the bolt forces more evenly around the plates.
The finished electrolyzer equipped with a bubbler. The bubbler is absolutely essential to prevent backfires from blowing up the electrolyzer. The electrolyzer may be filled with slightly acidic water (use vinegar) to neutralize any residual NaOH vapors in the output gas. It would be wise to use a non-return valve between the electrolyzer and bubbler to prevent bubbler water being pushed back into the electrolyzer in case of backfire.
The electrode plates after the electrolyzer had been used for some time. The chemical reactions occurring in the electrolyzer have slightly darkened the electrolyte. The use of 316 SS electrodes would probably have prevented this. Note how the other side of the plate is relatively clean, while the other side has a darker deposit. Note also the sanded and crosshatched electrode surface.