Rain water to make saltwater?

fishbulb

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Im sitting on the porch watching thousands of gallons of water fall from the sky and it got me to wondering,

Does anyone use rainwater to make saltwater?

What would you have to do to make it usable?

Is all rain water the same?

I’m not actually sure how you filter rain water, but I would recommend it. It picks up pollutants from the air and your roof if you are using rain barrels.

The issue I see is that usually city water that we pump into our RODI units is sterile. Thus funk does not grow in the sediment and carbon filters. Without that funk, the membrane is safe as well. Contaminated rain water could make a mess of an RO unit. I would check with RO filter manufacturers to see what they recommend. I could imagine treatment with a chlorine tablet before filtering or UV sterilization.

I’ve always had this ambition as well.
Cheers
FB
 

saullman

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Thank you for asking this question. I have been wondering this for a long time now, but always forgot to ask it. I live in Florida and we get a ton of rain water especially around this time of year. I live in a small town in Florida and our water bill is expensive for whatever reason so if there is a way to reuse rain water in our reef tanks I would like to know. Has anyone out there tried it and been successful?
 

EMeyer

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Its surprising the amount of misinformation about rainwater. Outside of dense urban areas or areas with otherwise lots of local pollution, rainwater is very pure, with lower TDS than city or well water. It generally has very low pH but thats a complete non-issue if you're making saltwater from it, since this is a buffered solution the initial pH of the water won't matter.

The method of collection may introduce substantial contamination, though (e.g. runoff from a roof).

I have a well and no water shortage, so I have no motivation to collect and store extra water, since my water is nearly free anyway. But in principle rainwater is pretty clean stuff.
 

ReefDude716

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Attempts to collect rain water. Turns out it’s acid rain lol but if you were to collect rain water I would assume in most cases your filtration systems will be worn out pretty quick and you would save money just using tap water to ro lol
 

Randy Holmes-Farley

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My primary concern would be whatever you use to collect it and store it, not anything it picks up from the air. To be concerned about that would imply one should be concerned about aerating a reef aquarium.

I wouldn't want to use rain collected off a normal roof for a variety of reasons, from leaching of chemicals from asphalt tiles to bird poop.
 

Alistairn1

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Im sitting on the porch watching thousands of gallons of water fall from the sky and it got me to wondering,

Does anyone use rainwater to make saltwater?

What would you have to do to make it usable?

Is all rain water the same?
Great idea and just get it to fill a good sized barrel, then as long as you use a pumped RO unit as the membrane requires pressure to run efficiently you’ll be good to go
 

Sisterlimonpot

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When water evaporates it is stripped of all it's minerals. Rain water is soft, no minerals.
Then it has to fall through the atmosphere land on many different surfaces picking up contaminants along the way. Definitely not pure by the point of collection.
 

fishbulb

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Great idea and just get it to fill a good sized barrel, then as long as you use a pumped RO unit as the membrane requires pressure to run efficiently you’ll be good to go

My concern for running the line directly from a rain barrel to the RO unit it that it will quickly foul the membrane and prefilters. At least the way I understand it, most RO units are fed with sterilized city water. I think you will be a lot of bacteria and microbes in rain water in a rain barrel. What do folks do with well water feeding an RO system?
 

fishbulb

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Then it has to fall through the atmosphere land on many different surfaces picking up contaminants along the way. Definitely not pure by the point of collection.

Agreed, I would call water off of our roof shingles pure by any means.
 

NashobaTek

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