Hey there. Obviously you have been doing due diligence on your research. Good for you. There is a lot to be said for saving water but I wouldn't do it short of a test for every chemical and bacteria under the sun. Looking at the lists of what can be found some of it makes me nervous and there is a lot that can't be filtered out. Some commonly found items are herbicides and pesticides. The oils from the roof materials are pretty toxic too but most of them can rise to the surface. But that takes time. Every pollutant in the atmosphere winds up in rain water and would go into the pond.The information I've found would make me avoid it if at all possible.

A good explanation is found in Freds Bog if you do a search on Garden Web. However I have to admit there are people who use roof run off and swear they have no problems. A few years ago after a severe hurricane, our area had a lot of damage to crops from the rain that resulted. Local home owners weren't reporting though, just farmers. My pond was devastated with dead plants and seriously sick and dead fish. I have to think there was a connection.It took the rest of the year to cure the pond.

I would only be concerned perhaps that the shingle material would leak fast enough some chemicals out. But then, consider that rains wash out of the atmosphere any pollutants into all agricultural fields, natural and artificial creeks and ponds and the oceans, so all get the same. There are people who conserve rain water from roofs in barrels and use it in their gardens and ponds, they must be believing it is OK.

During torrential rains possibly fertilizers and insecticides from surrounding plantings can wash into a pond when that pond is lower than the landscape.

I use rain barrels to collect water from the roof. I add to water to my bog garden (close to, but not connected to the pond), but I let the water settle to let particles from the roof sink to the bottom of the barrel. I haven't seen any bad effects to the bog plants, although I've hestitated to adding it to the pond, mainly due making the pond dirtier than it already is, in terms of things that blow into the pond.

If you look at the design of modern rain barrels you see the tap is placed close to the bottom but still several inches above it. This is to allow sedimentation to occur. The top is not tapped because that is where oils accumulate. You don't want to use the oil contaminated water. It is usually removed from the surface by allowing the barrel to gently overflow. The inside should resist oils rather than collect it on the sides. It takes at least 24 hours to settle sufficiently for use.

This still does not address those contaminants that are water soluble.

Hi
Have used rainwater from my roof for many years. In fact
the original purpose of the "pond" was a reservoir to store it. I even use it in my aquariums. I have a bypass
so around the first 30 gallons is diverted to the ground
. Then passes through an underground pipe to the bottom of the pool. Acts as a purge system if the rain is heavy enough. I do use a settlement barrels which is most useful when there are long periods between rains. Of course there is a large particle filter on the downspout.
gary

Gary,
Would you describe your bypass?
Thanks,
Ella

No, you won't pollute a pond with rainwater off a roof. Any trace amounts of whatever are going to be so infinitesimally small compared to the bio mass already in a pond, they will have no impact, they will be 'absorbed' as part of the bio mass

Now if it was well water or city water, there you might have serious levels of contaminants depending on what is being plonked into its watershed over the years.

All my rain water runs to planting areas of hostas, primulas and astilbes, never had a problem with plants.

There are few plants on my property. Maybe 15, not counting weeds that need removed. Those are mostly palms of some kind, and sage. There are a few native shrubs. There is an orange, if it wasn't killed in the cold weather recently. The main and only reason for spending any money on harveting and storing rainwater is to fill the pool/pond. Until the asphalt roof is replaced, I would not use that water in the house.
The pool has about 13000 gallons, and water is expensive in the desert. If I can use rain to top the pool off with, it would be worth the time, energy, and money needed to build a system.
Ella

So the question is still, is runoff from an (older) asphalt roof safe to use in a pool/pond?

Ella, I think the only way you will be able to answer this question is to collect some water from the roof and have it analysed. Collect the water before it has a chance to settle.

A new roof would have more petroleum runoff than an old one. I suspect best results would be with a tin roof.

Yes, I think both clay tile and galvanized steel roofs are okayed for potable water, with of course, filtering and I think, uv light. My roof appears to be in good shape. I haven't had it checked yet. At a guess, it's less than 10 years old, and roofs here last 12 to 20.
Good suggestion to have "fresh" rainwater analyzed. We haven't had any recently... I'll collect some when I can.
Ella

Almost all of my pond/stream water is from a mix of roof and french drain water. As far as I know, there are no ill effects. The fish and frogs seem fine. Dogs and birds drink it. I am dealing with soil laden water while you are only getting the roof water. Remember that the roof was rained on many times before you used it, so most of any possible problem has probably been diluted. I would bet that the skippy would be a more likely place for problems then the roof.