Originally Posted by CharlieD
I tried to search for the answer, but couldn't find anything here nor could i find anything scientifically based. More or les it is a here say, somethig tht I've heard many times and av sed itasexpalnationmy self. But in reality I do not think it quite woks that way. Liker example lead pipes racically noody ha lead pipes today. Not n th hoses buil lat 20 years.
Has anybody senn a more plosable expnation?
the 'scientific' answer is as stated - lead - and it's various salts / compounds - is much more soluble in hot water than in cold water.
'how much' did you ask - valid question. I did some surfing but did not come up with a graph of 'soubility vs temperature' - probably exists somewhere.
lead pipes still exist. in the mid 90's I did house rehabs - and it was std fare to discover a lead pipe from the street to the house; had to be replaced. also note, the lead pipe from the street to the house plays zero role in hot vs cold water - the water heater is downstream of the contamination source.....
high lead content solder was banned.
hard to find now-a-days.
but copper soldered joints are not the only source of lead in the "system" -
even if you have plastic pipes, you'll likely find brass / bronze / galvanized pipe fittings in the system as a transition from "metal" to plastic.
also - plumbing fixtures - faucets, taps, etc., can have high lead content - those were first limited in lead content in the mid 80's.
if you read the owner's manual for your hot water heater it's likely to advise an annual service action to drain the "junk" out of the bottom. they all come with drain valves at the bottom . . .
from first hand experience I can attest to the fact that water heaters accumulate a lot of "junk" at the bottom of the tank. I once spent half a day fishing and poking to get the accumulated "sediment" out so the bottom drain valve would run clear.
it is true that "hot" stuff rises, and it is true that the hot water supply is tapped off the upper reaches of a tank (and cold water is piped into the tank at the bottom...) - regardless - a hot water heater accumulates a lot of junk and certainly has the potential to flavor your (hot) water.
how problematic this issue may be is extremely variable - age of heater, water supply 'conditions', etc.
if you can determine "lead" is not an issue - all the rest is up for house-by-house grabs....