I had a problem with my hot water recently, which meant going for a couple of days without showers. I am thinking of getting some kind of low-tech camp shower in case this happens again, and was wondering if there was anything I should know about them.

My recent situation was a fairly specific failure; I had electrical power, gas and water, and could heat water in a kettle. I'd obviously prefer something that would be useful in a more general crisis, so I don't really want something with an electric pump. I've seen camping showers advertised that are basically black bags with a spout, and quite cheap. Whether I'll get a crisis in which water is plentiful enough to shower with, but no electricity, I don't know.

Another possible problem is how to rig it. The camping ones look like they are supposed to be hung from a tree, outside. I don't fancy showering outside during winter. They hold about 20 litres of water, which weighs about 20kg, which is pretty heavy, and I'm not sure how I'd support that at height in my bathroom.

Does anyone have any experience, advice or recommendations?