catchment recommendations? (Volcano: loft, house, earthquakes)

[escape from wisconsin]

I'm building a home in volcano area of the big island. Any recommendations on style of storage tank? What are the pros and cons? We've seen corrugated steel, plastic, and concrete. We also plan to put some kind of filter and perhaps UV. Thanks . . .

[hotzcatz]

Most folks use a "doughboy" swimming pool which would be the corrugated steel ones, put a cover on it and get their drinking water from County water taps. I know another person who has an in ground swimming pool as their water catchment but I'm not sure if I'd want to swim in my water supply like they do.

Volcano stays pretty misty so metal and such will corrode. Get galvanized steel, paint it and perhaps put a metal roof structure over the whole thing to keep the metal dry. The roof will also catch more water which could be piped into the tank. There are earthquakes so concrete tanks could be cracked during an earthquake. I suppose you could build a concrete tank and then line it with plastic. More expensive, though, than the traditional doughboy. Ask your neighbors and see how they are doing things. It will also give you a chance to chat with them.

[Idunn]

This site, which covers some aspects of Earthship water design, may prove helpful:
Earthship Water System
The climate is obviously different, but some principles will be exactly the same. For potable water you wish to insure that it never comes in contact with anything toxic. This starts with the roof (as in no asphalt shingles), or however water is collected, to pipes, storage containers, etc.

There are many sizes of plastic containers designed for potable water storage. Some containers are not designed for potable water, so know the difference. Vendors of those that are will state so quite clearly. Something less expensive would be to build your own cistern out of something such as concrete. A plastic coating can be easily applied which prevents leaks and makes this ideal for potable water. Make sure the coating is designed for potable water. A good place to look for these are suppliers that deal with fish ponds and such.

I'm more familiar with temperate mountain than tropical settings, but would guess you would have more of an issue with such things as algae growth. The basic principle however is to keep the stored water sealed from such things as mice, etc., and also dark. Keep the water from light, and keep it dark. Also as cool as possible, and for this and several other reasons not a bad idea to bury the cistern. Some will advocate chlorination or other chemical remedies, but these can be entirely dispensed with (and yourself better off) if the entire system properly designed and built. In filtration you have the option of such things as reverse osmosis which will do an excellent job removing bacteria and other impurities, but otherwise not taint the water.

Beyond all treatments you might try, first and foremost insure your water is properly stored. A little research into this will help a lot (there are many fine examples and lots of information available online).

[Jonah K]

Here's a link to a PDF of "Guidelines on Rainwater Catchment Systems for Hawai'i" -- a must read that should answer most questions....
http://www.ctahr.hawaii.edu/oc/freepubs/pdf/RM-12.pdf

[escape from wisconsin]

thanks to all for the info . . .

[kahakiihale]

I had great success with heavy ICF (also sold on island as Castleblock) catchment tanks. They are clean, healthy, and keep the water cool even in the middle of HPP. I design them into the foundation or lower level or under attached lanais of homes. They are waterproofed with a cement type of coating and so far have not cracked, not even in the big earthquakes of a few years back, not even holding up two levels of house plus a loft above. It is critical to have a good filtration system to clean the water before letting it into the tank. There are commercial units available from the mainland but someone should be building them on island, there would be a market here I would think.