Ever wonder what that big plastic green tank sitting on properties as you drive by?  This big ugly thing is called a cistern and is a holding tank for water.  This can be used for a catch basin for rainwater that is collected off of your roof down your gutters, an extra holding tank pumped out of your well if it doesn’t have a quick refresh or fill rate, or if you don’t have enough water in your well it could be a holding tank for water that you have trucked in.

Let’s start with a collection tank for the rainwater off of your roof.  This is a pretty cool idea to use the rainwater for either your watering or filtered for your household water.  Being on the island we sure have enough rain to capture and putting it to good use is a smart idea.  It is easy to do as your rain is collected anyways from your roof and gutters and then the downspout will just feed into the top of the cistern and done.

If your well has a slow refill rate, you can use the cistern as an extra holding tank so that if you are second in the cue to have a shower, you don’t run out of water.  The holding tank will be pumped from the well when it gets below the line that you set up or when the well gets enough water in it to pump some out.


Getting water trucked in is not the best, but it's what we have to do if we have a shortage.  This is pretty simple a big truck backs up and pumps the cistern full.  Normally people don’t have to do this often, maybe just in the hot month or months is when it is needed.  If this is a more common issue then a second cistern to collect the rainwater would be a good idea to keep the costs down in trucking it in.

There are a few other reasons that someone would have a cistern that are above my paygrade but for some of the sediment and sulfur in your water a cistern can filter some of that out before it hits your house system.

Are there any other options other than the big green tanks?  Some tanks go into your foundations now when you are building which is pretty cool.  These would be to collect the rainwater for use of your toilets, dishwasher, and any other item other than drinking which wouldn’t have to be filtered as much, and then your well would be just for drinking and cooking with.

Water is a pretty important item in your quality of living so make sure you talk to the water guys who are much more knowledgeable in what will work best for you but I hope this helps you understand just a bit more about what a cistern is and used for. 


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