Interestingly, the presence of lead pipe is due to an old safety
requirement for piping.
Iron pipe from the street to the house is prone to cracking from the
inevitable settling of backfill and other ground movements (along with
the main cast iron pipes used at the time for mains moving). These
cracks allowed ground water seepage at a time when many homes had out
houses, leading to the appearance of fun things like E. Coli in the
water along with possibly contaminated surface water.
The solution was to use lead or copper pipes and keep the pH of the
water above 8.00 -- this will prevent corrosion of the lead or copper
and keep the pipes from getting cracked.
Obviously, lead piping isn't a great idea in the long run, and in many
areas it has begun to corrode enough for various reasons to increase
the lead content in the water sitting in it above safe limits. In
Flint, changing from moderate carbonate content non-corrosive water to
highly corrosive (and fairly polluted water -- GM won't use it for
mill water) cause the pipes to corrode very badly and raise lead
levels to the point where children will have significant mental
development issues, which are permanent.
With the advent of plastic pipe in the 60's, nearly all water systems
quit using lead pipes in new construction, but left the old ones in
place. Hence the issue in many older areas if the water changes for
any reason and adequate anti-corrosives are not added. There is also
some evidence that the phosphates intended for this do not do a good
enough job, and one of the great infrastructure issues in cities these
days is finding and replacing all that lead pipe.
The issue is much worse in low income areas -- not only are the houses
more likely to have lead pipe, but the residents are much more likely
to be unable to pay the $1500 or so it takes to dig them out, and
landlords simply refuse.
Peter
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