Lead plumbing boot flashing safe?
We are having a standing seam metal roof installed and they are planning on using lead plumbing boot flashings to seal the roof roof vent pipe penetrations. I’m sure many of you have metal roofs so hopefully someone will be able to give some insight.
It sounds to me like the lead flashings are considered the method with the most longevity (vs something like those plastic boots), which is important in a metal roof since it should have a long lifetime before replacing.
I’m wondering, though, is there any concern with using lead? Could it happen that when it rains, a small amount of lead could get mixed with the water, and that water could carry the lead and accumulate in the soil that we use to garden with?
I don’t want to overreact about something like this — I want to minimize unnecessary exposure to toxic materials but don’t want to go overboard with avoiding every little thing. More of a balanced approach hopefully. So I’m trying to figure out if this is something to be concerned with and use a different material instead (and if so, figure out what that would be), or if the concern is so minor that I don’t worry about it. Thanks.
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Q. "Could it happen that when it rains, a small amount of lead could get mixed with the water, and that water could carry the lead and accumulate in the soil that we use to garden with?"
A. Yes, I think that's possible. I can't quantify the rate of leaching -- but eventually, lead does erode.
Lead is an excellent flashing -- long-lasting and flexible. Roofers love lead. But it is probably time to retire this useful flashing material. Safer options include copper, rubber (EPDM), etc.
The nice thing about boots for metal roofs is that, unlike those used for shingles, they sit on the surface and are sealed with caulking and gasketted screws. That makes them very easy to replace. A good rubber one will last decades. Plan to take a look at them every few years and change when they show signs of wear.