Shingle roof and rain water catchment

Hi all. My great regret was putting a new shingle roof on my house 2 years ago. I didn't realize at the time that it was the worst material to choose from a rain water harvesting perspective (and passive cooling perspective as well). I've been researching elastometric coatings that work with shingles that are certified for potable water catchment. Although there are some, there are also challenges. I spoke with a store that sells these products and their views are that shingles need to breathe and if you cover them with this type of paint, you will reduce their lifespan (but by how much? I don't know) and could result in mold if there is inadequate ventilation in the attic (I have 2 solar vent fans so am not concerned about that). Has anyone gone this route? What have your experiences been? Any other experiences catching rain water off of shingle roofs?

Perhaps a silt filter inline prior to your catchment?

Hi Mike. What part of the world are you in? I think that's relevant, especially if you have sustained intense heat.

Also, what is your intended use for the water you capture?

I had a bunch of my roofs reshingled two years ago. My observation is that these shingles are light years away from the old bitumen goo shingles they replaced.

I still expected some offgassing/seeping etc. for the first year, so the water collected was used for trees. Healthy soil can break down small amounts of hydrocarbons. But I wasn't willing to risk direct use on vegetables.

So personally, I don't see your situation as a disaster, only a problem to be managed. Though if that was my primary water source, I would be inclined to run it through a Big Berkey or equivalent, just for luck. My 2c.

Thanks for your insight, Douglas. I am in south east florida - a hot, subtropical climate. My ideal use for the water would be (1) vegetable garden and (2) outdoor showering. Long-term, I'd like to offload as much of my water use to rain water as possible. In my region, aquifers are often under strain. Too much development, too many people, no concern for managing storm water run off... It's just a mess. I'd like to reduce my burden on the aquifer to the extent possible.

In Florida you usually get a heavy rain every evening right?  I've seen some of those rains, a lot of volume in a very short time. Could you construct a covered patio or shed or something with a metal roof and oversized gutters to collect with?  It may not get you all the rain you require but as it's often a daily rain and if you have enough storage you may be surprised how much you actually collect.  We turned on our system last spring out here in the Seattle area (where it rains a lot but it's a light rain, nothing like the heavy rains you get) and filled the 7500 gallons of storage we have in 48 hours.  Volume of rain falling on a roof is hard to quantify by watching it but adds up quick when routed into a tank.  We use our rainwater for irrigation of our garden and landscaping as we're on a well we share with 7 other homes.  The water meter I installed on the system read a little over 14,000 gallons when I winterized the system a few weeks ago so we can say with certainty that we DIDN'T use 14000 of potable water for irrigation this year

I second the idea of filtering it if it is for your consumption. Other than tha I'd say you are good to go. I collect rainwater of a shingle roof for my garden and I am still alive.

If there are heavy rains, the use of a first flow/flush diverter may be worthwhile. It automatically diverts the first wash of roof crud (bio, chemical, fallout?) and then moves the rest into your storage tanks. Sound idea IMO.