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Plumbosolvency
Frequently
Asked Questions
What is plumbosolvent
water?
Plumbosolvent water is water that
can dissolve metals. If left undisturbed for several hours in a
pipe or on a metal surface it absorbs small amounts of dissolved
metals which can then be delivered via the tap to your glass,
cup or kettle.
In New Zealand,
the heavy metals that dissolve in drinking water from plumbing
fittings are lead, nickel, cadmium, copper and antimony.
All water is
plumbosolvent to some extent, but soft, slightly acidic water
dissolves metals most readily. Roof water that has not been
stored in concrete tanks (which make the water alkaline) tend to
be acidic because of dissolved CO2 which forms the
weakly acidic carbonic acid when dissolved in water.
Can heavy metals affect my health?
Yes they can,
whether they come from drinking-water, air or food. However,
water that has
safe levels
of heavy metals poses no risk.
Lead is the
main heavy metal in drinking-water and the one that poses the
greatest health concern. Lead cannot be removed from the body,
so it builds up in the skeleton and can damage nerves and
organs. Infants, children and pregnant women are most
susceptible to lead’s toxic effects, which can include brain and
kidney damage.
Where do lead and other heavy metals in drinking water come
from?
In most houses,
especially older ones, heavy metals come from the taps and from
the solder in the fittings that connect the taps to the pipes.
The brass alloy used to make the taps can contain a low
percentage of lead, and a very small amount of this lead is
released into the water when the water stands in the tap.
Copper residues
can also come from cold water pipes made of copper.
Heavy metals
can also leach from roof and guttering materials into rainwater
collected for water supply.
Is
plumbosolvent water poor quality water?
Plumbosolvent
water is usually of good chemical quality so long as it does not
have prolonged contact with metals.
How do I know whether or not my water is plumbosolvent?
Natural water
that is used for water supply in New Zealand is often soft and
mildly acidic. All water supplies are therefore classified as
plumbosolvent until the water supply authority can show that
their supply is not plumbosolvent.
Blue or green
staining in the sink, often under the hot tap, is an indication
that the water is plumbosolvent to a degree (and that the washer
should be changed!)
What are the health authorities doing to address the problem of
heavy metals in water?
To comply with the Ministry of Health’s
Drinking-water Standards for New Zealand a water supply authority with
plumbosolvent water must advise its consumers twice a year how
to minimise heavy metal levels in their drinking water.
What can I do to avoid drinking water containing heavy metals?
Get into the habit of flushing the first half-litre –
500 ml - from the cold tap every morning and after a long
absence.
If your house
has a rainwater supply, check your roof and guttering for
materials that may contain metals that could contaminate the
water: lead flashing, lead-headed nails, and lead paint, for
example. These should be replaced if you find them.
Flushing cannot
easily rid drinking water of copper if copper is being released
from copper pipes. Copper is much less of a health concern than
the other heavy metals, and levels that might be a health
concern do not arise often, but baths and sinks can become
stained blue or green.
Do I need to
flush the hot water tap?
No. You only
need to flush water that is going to end up in your mouth. Water
from the hot tap is not usually used for drinking or cooking so
will not usually need to be flushed.
In fact, hot
tap water is likely to have higher levels of heavy metals than
cold water because of the higher temperature. This is one reason
why it should not be used in drinks and food preparation.
What if I accidentally swallow some hot water while taking a
bath or shower?
The health
effects of metals generally develop as a result of repeated
swallowing over a long period of time.
Swallowing an
occasional small amount of water, even if it contains a high
metal concentration, will not have a health effect.
The one
exception to this is copper. A high concentration of this metal
can cause vomiting.
Will boiling the water reduce the risk to my health from heavy
metals?
No. Unlike
bacteria, heavy metals are not destroyed or changed by
boiling. In fact, because of the loss of water as steam, boiling
may slightly increase the concentration of metal particles in
the water.
Isn't flushing the first 500 ml
of tap water wasteful?
The first 500
ml to come out of the tap is only a small fraction (0.25%) of
the estimated 200-250 litres of water that each person uses each
day.
However,
everybody should try to save water whenever they can. So,
instead of letting it run down the plughole, save the first half
litre from your cold tap to use in watering pot plants (but not the vege garden) or washing dishes (always remembering to drain and wipe them
afterwards).
Can I check the metal content of our water myself, and how do I
do it?
Yes, you can
check the water yourself, but you will need a laboratory to test
the water, someone to explain what the results mean, and money
to pay the laboratory services. A health protection officer
from the District Health Board may be able to help with
explaining the results.
To collect the
sample:
-
Contact the
environmental health officer at your council offices and ask
for the address of a testing laboratory.
-
Collect the
correct sampling containers from the laboratory; a container
you have cleaned yourself will not give reliable results.
-
Allow the
water to stand overnight before taking the sample first
thing in the morning. Take the sample from the kitchen
tap. Make sure nobody uses the tap during the night before
the sample is taken.
-
Fill the
sample bottle almost to the top but without it overflowing.
-
Take the
sample to the laboratory for testing. You will need to tell
them which metals you want tested. Lead is most important,
but you may also wish to check on the levels of nickel,
cadmium and copper in the water.
The results
from this sample will tell you how much heavy metal was in the
sample of water that was standing in the tap if the tap was not
flushed first. However, different samples will have
different concentrations of lead in them, depending on temperature, the length of time that the water
was in contact with the fitting, the composition of the fitting,
etc.
For this
reason, sampling the water will only tell you that the water was
plumbosolvent, but will not tell you how plumbosolvent. That's
why the results cannot
be used for comparative purposes.
If you wish to
know what the metal concentration will be after you have flushed
the tap, remove two glasses of water before taking the
sample. You may wish to get two sampling containers from the
laboratory so you can take the second sample after you have
taken the first sample and flushed the tap.
Where can I get some more technical facts on this?
Glad you asked. Just
click here
Safe means a concentration less than the
maximum acceptable value (MAV) listed in the
Drinking-water Standards for New Zealand. The MAV is the concentration of a metal that, on the basis
of present knowledge, is not considered to cause a health risk
even if the water with that concentration of the metal is
consumed for a lifetime.
