Transcript Non-Leaded Brass

Lead in New Buildings:
UNC CHAPEL HILL
Marc Edwards

Background: Lead in New Buildings.

Preliminary Findings on Lead at UNC
– Focus on the worst samples
– How bad is/was the problem?

Mitigating the Problem:
– Short-term:
– Intermediate-term:
– Longer-term:
Minimizing Exposure/Flushing
Fine-tuning the Chemistry
Changing the Plumbing Code
The Cause of the Problem
“Lead Free” Brass

1986 Safe Drinking Water Act Lead Ban
– Pipes and solders < 0.2% lead by weight
– Brass < 8% lead by weight
Lead free brass can legally contain
up to 8% lead by weight
Also pumps, valves, water meters, backflow preventors, etc.
Why Leaded Brass in the
First Place?

Pb (up to 8% by weight) added to
brass in order to:
– seal leaks
– improve corrosion resistance
– ease machining of intricate brass devices
Most modern brass products contain < 3% Pb
Other information
Higher purity waters (lower alkalinity, etc)
more likely to leach lead from brass
 Rainwater and distilled water extremely
aggressive
 Water at UNC is very pure
 Corrosivity mostly countered by raising pH
and adding inhibitor

In most cases
lead leaching
from brass drops
off with age…
40
Pb (ppb)
30
20
LCR Action Level: 15 ppb
10
Test Water
0
3
4
5
10
11
12
Sampling Day #
17
18
19
But some waters
are more
aggressive to brass,
and cause lead
leaching to rise for
a time before
falling…
40
Pb (ppb)
30
Low AlkalinityLow pH Water
20
LCR Action Level: 15 ppb
NSF Test Water
10
0
3
4
5
10
11
12
17
18
Sampling Day #
Lower pH-Lower Alkalinity Water more aggressive
19
10x
UNC LEAD PROBLEM

UNIVERSITY WAS VERY AGGRESSIVE IN
SEEKING OUT “WORST CASE” SAMPLES
– Removed brass plug to sample water from
backflow preventor
– Removed aerators to sample faucets
– Sampled hot water
MANY SAMPLES COLLECTED WITH
ALARMING LEVELS OF LEAD (> 500 ppb)
No alarming lead values came from
appropriate samples of drinking water….
Removing brass plugs and aerators before
sampling, creates metal “turnings,”
essentially adding fine pieces of brass to
samples and giving high lead values
 Lead values in recent sampling using
conventional approaches indicates a
significant, lower level lead problem,
consistent with brass in new builds

“Beres” Samples
6 samples collected afternoon of 2/13/07
 Caudill Labs floors G, 1 and 3 specifically the
Men's restroom faucets and the drinking
fountains in the SW corridor
 No building flushing at the time and
representative of water people were drinking
(but not first draw)

5 of 6 samples tested:
Highest lead was 3.3 ppb
“Beres” Samples (Cont’d)


143 – 313 ppb Cu
25 - 270 ppb Zn
Group taste threshold for Cu+2 =
400 ppb
Evaluation of Copper Speciation and Water Quality Factors That Affect
Aqueous Copper Tasting Response
Jonathan D. Cuppett, Susan E. Duncan and Andrea M. Dietrich
Chemical Senses 2006 31(7):689-697; doi:10.1093/chemse/bjl010
The lower level lead problem has
responded well to flushing and
cleaning of aerators
Building pipes were not thoroughly
cleaned with aerators off when
commissioned, or if it was cleaned, it was
not successful
 Flushing drops lead by removing
sediments and hastening formation of
protective film on brass

CAUSE OF THE LOW
LEVEL LEAD PROBLEM
8.0 x 10-3 in2/mL
Meringue dezincification
> pH 8.2
 High Ratio

– Cl-:HCO3
Hot Water
Zinc enriched scale forming in
brass from home with
complaint elsewhere in water
system
Turner Diagram
(15 mg/L hardness, 14 mg/L Cl-)
OWASA Lead Study
(12 waters x triplicate conditions)
Preliminary
Trends
(OWASA RESEARCH)
18
t = 6 days
16
Lead (ppb)
14
Unusual problem can
get better
at lower pH!
12
10
8
6
4
2
0
pH 8.3, 0.2 PP
pH 7.7, 0.2 PP
pH 7.7, 0.5 Zn oP
Legislation

Lead Free Drinking Water Act
– Would reduce allowable lead to 0.25%
– Reintroduced a few weeks ago

CA Assembly Bill 1953
– Limits the amount of lead in brass at wetted
surfaces to < 0.25%
Acknowledgements
UNC Administration
 OWASA
