by CaptnAwesome » Mon Nov 28, 2011 2:00 am
This probably stopped being relevant 4 months ago when he asked, but for everyone else...
I forget which alloy, but, buy food-grade stainless. But it, maybe used, as a big sheet and then coil it into a tube, weld a top and bottom onto it.
All stainless will rust under some conditions. Inconel is a ridiculously expensive alternative (more corrosion resistant, used in ocean environments). They make water towers and breweries out of stainless tubes, so, I think it'll be fine.
Galvanized steel doesn't have lead in it, as far as I know. However, unlike stainless which is stainless solid all the way through, galvanized steel is just normal cheap steel coated with a sacrificial layer of zinc. Metalurically it's ordinary steel with a slight chemical paint job. It eventually wears or abrades off, and then you have normal mild steel underneath (rust factory). Also, heating anything galvanized is deadly, zinc fumes are highly toxic and lead to delusions and organ failure almost immediately. Nasty stuff.
Beer kegs I thought were usually made out of aluminum. Soda containers are indeed stainless but only a few gallons each.
Don't be stupid and use glass. It's fragile and your chances of blowing your own massive glass tank and then having it cool without microfractures is next to nill. My guess is you'd end up wasting most of your time.
Copper is 100x the price of steel. Brass slightly less (and will cost you less because it can be thinner, using less metal since it's stronger). Interestingly, both kill germs after a few minutes (for example, on doorknobs). Neither are a good idea for water tanks though, way too expensive.
The link between aluminum and Alzheimer's has not been proven, or even demonstrated. IIRC the one study that was done was found to have slight increases of Alzheimer's relative to the normal population, but there was no control group and the group affected was old people (who are likely to develop it anyway). Aluminum doesn't generally corrode, it has a self-sacrificial surface layer of aluminum oxide (aluminum rust). However unlike oxidized iron (rust), aluminum oxide is one of the harder materials known to man and doesn't flake and dissolve, and it's also self-repairing. If any gets scraped off, as soon as the new pure alum surface touches air, the oxygen bonds to it and creates a new protective layer. Aluminum will be 2-3 more expensive than stainless though.
Plastic is simple and easy, I'd just go with plastic if you're not doing long-term storage. Housing pipes are all plastic now-a-days. Storage tanks are only not-plastic if they need to be structurally strong and impact resistant for some reason. Yes, some types of plastic leach chemicals into the water, so, use food-grade plastics (standard Rubbermaids might even be the right type). The bigger danger with chemical plastic is if the water is sitting there for long periods of time. Then, large amounts of chemicals will have leached into a small amount of water. So, don't get a huge tank and then fill it once a year. Get a medium tank and fill/drain it once a month or more. Also, the bigger the tank, the safer, because the surface area:volume ratio will be smaller. That is, don't stack up 500 water bottles. There's lots of surface area relative to the water. If you were to make them one big bottle, you'd cut away all the internal bits and leave only the perimeter. Plastic's only dangerous if you drink only storebought, handheld bottled water, where there's high surface area, and it's been sitting for many months each.
