chemrox - 30-7-2008 at 21:45
This is not a school problem. The wires to a submersible pump carry 115 volts. make any reasonable assumptions about amps to allow the pump to lift
water 200 feet at 5 gpm. The well is allegedly contaminated from lead because of the soldered connections to the pump. Assume each of two
connections contains 100 mg solder as pure Pb and that a minimum of 25 mg is necessary to maintain the connection. Assume the detection limit for Pb
in water by the method used is 5 ug/l. Assume the daily use is 550 gallons. How long can the well be pumped with pb being detected at every analysis
at or above the detection limit before the pump stops from broken connection(s) due to solder loss?
It has been proposed that Pb found in wells in the midwest is from the solder and we doubt it but we haven't done the calcs and you're all invited to
participate. I'm wokring on it too and will post my results when I get done but I'm strapped for time right now so it may be a few weeks. enjoy!
Cheers,
cRX
UnintentionalChaos - 30-7-2008 at 23:15
Well, going by basic math....
Two connections losing at most 150mg of lead combined would mean 150,000ug of lead total. 550 gallons of water are used per day, or 3.785*550 =
2081.75 liters per day. If lead is leaching at a rate such that it can always be detected, each liter must carry at least 5ug, which means 2081.75*5 =
10408.75 ug of lead leaches per day. At that rate, it would take about 14.4 days for the connection to fail. I think not.
Twospoons - 31-7-2008 at 14:24
You must mean solder on the pipes, right? Because if it was the electrical connections that were immersed they wouldn't last a day.