Haha, you could be right that the good old gaffa tape is holding the tanks form....... But i doubt it.
At the moment i dont fill my tank full, due to the modifications ive made in the back of the van, so it keeps the weight OK. So im probably only filling maybe 350 - 400 litres or so and also running the immersion for less time to compensate. I have a little vent hole at the opposite side ofmy tank with a push fit ball tap, but only so much steam can escape through a 6mm pipe. Over my main lid I place a cloth to stop water leakage as these lids ive never found to be water tight and this fixes that problem. I havr cut a slit in the cloth to allow steam to escape through the lid which is vented (seen on my van layout vids). But im guessing the open space in the tank was full of steam, so when i took the lid off, it had its chance to escape. Pending water temp when i fill her up next time, i might try n cut another hour of the time.
Yes shrek im cleaning virtually clean windows, but one round is in an area where alot of birds keep nesting and guaranteed after two days or so of clean windows they will get bird muck back on for a couple of weeks before im back there.
Im also picking up alot of new work and hot is way more superior on first cleans than cold and chemicals. I know dome will feelna strong urge to say opposite but in my opinion you would be wrong.
Hot water cuts through algae mess really easy and stubborn marks as well.