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I am working on creating blueprints for my new home. My plan is to have both solar panels on the roof and a rainwater catchment system that directs water from the roof into some tanks in the basement. I expect to have a filter (not sure if it will be ceramic, fiber, etc.) somewhere between the tanks and the pump that will push the water into a bladder tank before it reaches the household pipes.

I know you can have solar panels on the roof, and I know you can harvest rainwater from the roof, but is there some health risk in harvesting rainwater that has fallen on solar panels (and the racks, cables, etc.)? Do I need to worry about any chemicals being leached into the water? If so, what would be the best way to filter them out? I plan to use this rainwater for drinking and cooking.

Note: I already plan to have a filter for things like bird droppings and other biomatter. My question is specifically about substances that could leach off the solar panels or any related hardware.

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    The exterior of solar panels is pretty well sealed with just aluminum and glass, so I don't think that's much cause for concern. If the wiring was sitting in water, that might be a problem, but I would recommend making sure that doesn't happen regardless. – Nate Strickland Apr 11 at 16:37
  • Roofs are generally pretty horrible places to put solar panels if you have any other choice. They do cool the roof somewhat, but they create a bunch of roof penetrations and cause leaks, which are then hard to repair because the solar panel is in the way. Also firemen do not like them because they're in the way of firefighting, and misconfigured, they can zap firemen unless specifically designed to avoid that, and firemen don't trust that you did that. – Harper Apr 12 at 1:00
  • Health risks with making potable water is out of scope, as the answer basically states you'll got a hellva lot of research to do for that. - Do solar panels contain toxins that might leach into water? – Mazura Apr 12 at 2:11
  • Will this be your only water source, or a supplement? If the only source, have you verified that you can permit this? My county will not issue a building permit until you prove that water is available - either a letter from municipal water system stating that they will provide water, or water flow and quality test results from a well. – Mark Apr 12 at 15:13
  • @Mark I will initially have municipal water as a backup, so the permit is not an issue. – Pedro Apr 12 at 15:31
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If you plan to use that collected water for drinking and cooking then you will need a proper filtration / treatment system... Ingesting diluted bird-droppings is not a good idea...

So, a simple filter may not be enough, you may well need UV treatment, but you should consult the authorities for the standards in your location you are legislated to meet and consult some just for your own health and others who may drink your water...

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    This guy knows what he's talking about. They don't call him Solar Mike for no reason ;) – JPhi1618 Apr 11 at 17:16
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    I understand the need to filter out the gunk that accumulates on my roof. My question is specifically about whether I should worry about other substances that could originate from the solar panels. Would UV treatment do anything about that? – Pedro Apr 11 at 21:33
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    If your able to filter out the potential toxins present in rain water and make it safe to drink you will not have any trouble with water that has contacted the solar panels. Photovoltaic and hydronic solar collectors both use glass and aluminum mostly and are sealed up very well. Treating gray water for potable consumption at home is something that I have never heard about. It's going to be far more expensive than municipal water. – Joe Fala Apr 12 at 3:07
  • @Pedro no, uv justs kills bacteria, but filters like reverse osmosis would... – Solar Mike Apr 12 at 4:03
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    This doesn't answer the question... Any impact because of the solar panels or not? – Puck Apr 12 at 7:58
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No, it isn't, but not because of the solar panels.

If you have access to municipal water, there's no economically viable way to make rainwater potable. Roughly speaking, rainwater is about as dirty as "grey" waste water (from sinks, showers etc.) and it needs a similar amount of processing before (re)use. Rainwater contains all kinds of pollutants from the air plus whatever gets leached from your roof and gutters, so it's not really clean in any sense.

There are many possible uses for treated rainwater and grey waters, with each successive level having more stringent requirements (and thus being several times more expensive):

  • Garden, toilets: You only need to remove solid particles (tiny grains of sand and the like) to prevent clogging your toilet tank fill valve and to make sure the water's not too smelly (you don't want your toilet to smell worse after flushing than before, which is what happens if you use stale water). You just need to make sure you store the water in an underground tank (constant low temperature), don't store it for too long (2-3 weeks maximum) and use a simple filter.

  • Washing clothes: More filtering (carbon filter) needed to prevent clothes from getting discolored and really smelly.

  • Showers, baths, sinks: Need to eliminate bacteria and viruses. There will be lots of them in the tank and your shower will gladly disperse them into the air and you will be breathing them, with unpleasant results. You thus need UV treatment, ozone, or chlorination.

  • Drinking and cooking: You need to get rid of all kinds of dangerous metal ions, nitrates/nitrites, carcinogenic micrometer-sized dust particles, volatile organic compounds, chemicals leached from plastics and so on (this would also take care of whatever comes from the solar panels). This is a real technical challenge. Reverse osmosis or distillation is not an answer – it will remove all ions, making the water not potable. (Drinking distilled water will kill you pretty quickly.) Ion exchange columns won't remove small organic pollutants, and so on.

Given that water usage also usually decreases in this order, it usually makes sense to only do the first two levels. If you're in a really dry region where municipal water is extremely expensive or unreliable and/or you want your house to run super-green (even though it doesn't make sense economically), you can consider the third level (personal hygiene uses) as well. But making rainwater potable? Only if you really don't have any other source of water.

  • Sorry, I worked at a place that had all its water from a reservoir fed by rain and streams. This was treated to two levels non-potable and potable to meet the relevant standards, so it is very possible and technically feasible... sand filters, UV, reverse osmosis etc – Solar Mike Apr 12 at 9:48
  • @SolarMike OK, that was a bit of an overstatement. My point was that you need to replicate all the treatment that goes into municipal water, plus something extra on top of that because rainwater is a really crappy water to start with. – TooTea Apr 12 at 9:54
  • Economically viable does also depend on where you need the water and where you can get it from... If it is cheaper to treat on-site compared to transporting it... – Solar Mike Apr 12 at 9:56
  • @SolarMike Fair point, is it better now? – TooTea Apr 12 at 10:01

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