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I am building a house and wanting to do rain water collection to help fill an aquaponics tank, garden water, ect.

I was looking at metal roofing but not sure what I need that won't kill the fish. I can't find any info on this.

Any one have such info?


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I would guess the only possible contamination off your roof would be trace metals (like iron) in your water, and maybe paint chips over time. I would think that ground water has more trace metals, then normal rain water even if it is coming off your roof. I would say the only way to make sure is to test the water that run off someone else roof and see what you find. Or ask for a sample and do a simple test by soaking the material in water and removing it and seeing what it dose to your water quality.

Well for sure you wouldn't want a copper roof and I think any kind of galvanized roof isn't any good either. If you can get roofing material made out of HDPE plastic you should be pretty safe.

Yeah, I'd definitely copper and any zinc (so anything galvanized is out of the question). Aluminum only really becomes a problem for fish at pH levels that would probably never be a problem with AP (since your bio-filter would have crashed long before that would become a problem)...but using aluminum seems kinda freaky from the 'human health' aspect...(to me anyways)... 

There are bitumin coatings that can be used for potable water (but if you live in an agricultural area where theres lot's of spraying and you use a butimine product, to say coat the insides of your galvanized steel gutters, it would seem wise to incorporate a means to "flush off" the first bit of water that comes off the rain collection system...maybe divert it somewhere else (non-AP) for the first few minutes, before going into your AP catchment tank...since certain hydrocarbons and airborne chemicals seem to collect on bitumine...

HDPE, is certainly a good choice. I don't live in your area, so I'm not hip to what's available in the States...

Oh yes, first flush is a must for rain water collection.

So the plants wouldn't uptake the the zinc in the levels galvanized would put off before it killed the fish?

Aluminum I'm sure is quite pricy, plus the human health issues like you say.

Is HDPE made into rigid roof panels? I'd have to look.

I'll have to look up this bitumin coating. Thanks

Would a sand filter take out the zinc?

On second thought you should call rainwater collection experts that sell systems... they will have all the answers. Let us know what you find out.

I don't know of any around me, I'll reach out on the internet. My issue is that they say galvanized is fine to use for human consumption from what I've read, but it's not ok for an aquaponics system. So I don't know that they'll know what's good for fish. I'll poke around more

Devoid, a sand filter probably wont take out the zinc, and any chelating agents that you could use would probably cause more harm than good...Rigid u-PVC seems doable along with the a fore mentioned plastics. Though some UV stabilization would seem to be in order. Coating the galvanized metal to create a barrier between it and the water might be a good bet. Painting galved metal comes with it's own set of considerations, but you might want to look into that as well while you're at it...

reply deleted, I'll check the discussion. thanks

I used this as a roof over my fish tank for shade and also to collect rain water. I have been pleased with the look and results.

I got it at my local Home Depot.


Standard up to date (modern) painted metal roofing will not contaminate anything. I assume you are talking about the green, brown, white, etc metal roof panels. I would be much more concerned with what is in your rain water than what your metal roof will add to your system. I am building my system in a GH in order to avoid rain water. Call me paranoid but I have learned way too much about chem trail geo engineering to trust any rain water in the US. Google it and learn before relying on rain as your source unless you are on city fluoridated water then yes, rain is the lesser of 2 evils. If you are on city water: MOVE.

Check with Jason Garvey.. He is the best expert I know on the subject and rund a rainwater recapture company and is an amazing Aquaponics Instructor.

I don't know of any roofing membranes made of HDPE that are intended for exposure to UV. There are FRP panels out there that are inexpensive and pretty inert - used for outbuildings mostly. See Resolite. Exposed galvanized metal wouldn't be recommended for contact with potable water and won't last forever without a coating. Most painted metal roofing is either silicone polyester coated (inexpensive) or PVDF coated (longer lasting); either would likely be okay as a water collection substrate. But concerns over either particulate matter in the collection system and nasty stuff in the air remain; I guess we should be wearing masks and not eating or drinking anything.

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