Rainwater Reservoir for my Reef Tank

reef46

reef46

Member
Hey Everyone,
It has been a long time since I started a thread. I am moving into a new place in a few months and am going to do things right. I'm tring to go somewhat "green". I have purchased a 750gallon water reservoir that I will be hooking up to my gutter system for various uses around the house: gardening, fill the fountain, wash the car, ect.
My question that I pose to the group is this. If I were to attach my RO/DI unit to the reservoir, would I be able to use the filtered water (pending test results are good).
My reasoning behind this is not really to save much money, just to be alittle more eco concious.
Your comments are much appreciated
P.S. The reservoir is made of plastic.
 
natclanwy

natclanwy

Active Member
If you run the water through your RO/DI system I don't see any reason why you couldn't use it in your tank. You will need a pump to feed the RO/DI filter though.
 
scsinet

scsinet

Active Member
Not only will you need a feed pump, you'll need one that boosts the pressure to city water pressures. I would not recommend using a standard jet pump or sprinkler pump for this, as the amount of electricity needed to run it would be so high compared to the job it's doing (creating a small amount of RO water) that it would probably negate your "green" initiative. A small RODI booster pump may work, but these are designed to have a certain amount of pressure into them.
One alternate idea... why not use city water for the RO, and dump the waste line into your collection tank? That way you don't have to horse around with pumps and pressures, you are still recovering water for your green project, and you have no worried about water quality?
 
reef46

reef46

Member
I didnt think about the pumps needed to run this water through the filter. I was thinking of relying on all of the pressure build up from gravity being that the tank is 10 feet tall.
I'll probably give it a shot and if it deos not work with gravity I will just run the discarded water to the resevoir.
Thanks for the posts!
 
scsinet

scsinet

Active Member
Actually you can figure out the pressure mathematically before you even do it, and potentially save you some headache.
When you have a tank of water feeding via gravity, the size of the tank doesn't matter, only the height. In other words, a 10 foot tall tank that is 1 foot across will provide the same pressure at the bottom as a 10 foot tall tank that is 10 feet across. It's all about height and height alone - or, more to the point, the height of the water (Obviously the pressure will drop as the tank empties).
We also know that RODI units require approximately 50-60psi to operate correctly, as this is considered average city water pressure.
To figure water pressure, you calculate the weight of a 1" square column of water that is X high.
Water weighs something on the order of 0.037 lbs/cubic inch.
So, if your tank is 10 feet high, that's 120 inches. Assuming the tank is full, that's 120 * 0.037 = 4.44 PSI.
Or, to put it another way, to rival city water pressures, the tank would have to be about 113 feet high ( (50/0.037) / 12 = ~113 ), or lifted 113 feet off the ground, like a water tower does.
Just for the record, if you were thinking that you could gravity feed sprinklers, this is also likely to not work, but they make pumps that are especially designed for this purpose that provide city water pressures, so I wouldn't let this data dissuade me from the project, it's just that running a large pump like this for hours on end to produce only a few gallons of RO would be more waste than good. But for running sprinklers, if I had access to the tank, I'd do this project in a heartbeat!
 
reef46

reef46

Member
How'd you get so smart?!?! I appreciate your input. I'm gonna start looking for pumps for my sprinklers! :)
 
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