Cistern Size

Depends on alot on details/lifestyle.

Pool?
Teenagers?
Do you mind actively conserving water?
Will you water garden?

I have 10K gallon cistern, two people, we don't worry about conserving for household (long showers, we flush everytime, don't have to wait for a full load for laundry), no pool, don't water lawn, mid-island....

Rarely drop below 50% capacity.

http://www.phys.ufl.edu/~liz/water.html

This has some good info. Don't forget the dry times. I do ok with 10,000 gallons for 2+ people and a small garden. I usually have to buy 2 truckloads a year, 3200 gallons each at a cost of @ $300 a load. Ther is a corralation bewteen the cost of a cistern, about $1-1.25 per gallon of storage and the cost of water about 1- 3 cents per gallon.

there are certain minimum size requirements based on your roof area as well, so want to make sure you are meeting the codes in that regard.

http://webpac.uvi.edu/imls/cri_uvi/caprpt2/cisternsystems.pdf

The U.S. Virgin Islands specifies that
cisterns for hotels or multi-family
dwellings have a minimum capacity of
10 gallons per square foot of roof area
for buildings of one story, and 15 gallons
per square foot of roof area for multistory
buildings, although the
requirement is waived for buildings with
access to centralized potable water
systems.

Thank you all so much for information on cisterns sizes! I think I can now figure out water usage for people. What I'm having a hard time doing is figuring out how many gal. of water will it take to keep my heavily planted acre green all year long on the East End of St. Croix. I'm trying to install plants that are lush looking and drought tolerant, but I will have a lot of landscape material when I'm finished. Do any of you know how much water you use in your garden each typical year???

I use drip irrigation and water with 1/2 gallon per hour drip heads and have 20 heads so I water @ 1 hour a day , some times twice so @ 10 to 20 gallons a day plus what I hose on to the palms so probably aboy 30 gallons or less per day

We use a grey water cistern (5,000 gal) to catch the shower and laundry water.This greatly helps the septic system. You have to be careful not to use borate cleaners in the laundry.Borax and like products are very toxic to plants. I use very little laundry soap because the water is soft rain water. Same in the shower, a little soap goes a very long way This system works well with drip irrigation. You don't want to spray grey water, but it is fairly safe to use as drip or soaker hose irrigation. Be sure to mark any grey water outlets so no one drinks it by mistake.I'm on the east end of STX and we haven't had to buy water in 6 years. Saving water and saving power is a way of life. Once you adjust your old habits it seems easy and second nature.As for your landscape, once established most plants will do OK with less water.

Doug

@east_end_doug Hello ?? Did you install your grey water tank to collect your shower and laundry water yourself or did you hire someone to help you with it, If you hired someone can you please share their contact information? Catching the grey water from shower and laundry is something my husband I are very interested in and curious about pricing and how to best accomplish this ?

@littlemisssunrise PVC pipe is extremely easy to work with. Watch a few YouTube videos and you'll be a pro in no time.