Plumbosolvency Water


Here is a word that comes with a health warning!

Plumbosolvency happens when water dissolves heavy metals. Small amounts of lead and other heavy metals can accumulate in water that is left sitting in a pipe fitting for a while and these metals can end up in your glass of water.

Although the health risk is small it is cumulative, so the Ministry of Health recommends that you tip out that first 500 ml of water run from the cold tap in the morning and again after returning home at the end of the day. Boiling the water does not reduce the risk.

Please don't tip the water down the drain. Instead, pour it onto your pot plants (but not your vege patch) or save it for washing dishes (which you then drain and wipe).

FAQ's - Answers to frequently asked questions

What is plumbosolvent water?

Plumbosolvent waters are slightly acidic waters that can dissolve metals that they come into contact with. 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. 

Heavy metals commonly dissolved in drinking water from household plumbing fittings include 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?

Heavy metals are a health concern whether they come from drinking water, air or food. The Ministry of Health believes that the risk from heavy metals in drinking water is small.​ However, as a precaution it is recommended by the Ministry of Health that all households flush a mugful (500ml) of water from their drinkingwater tap each morning to eliminate the risk.

Infants, children and pregnant women are more susceptible to the toxic effects of heavy metals, so steps should be taken to reduce heavy metal concentrations in water that may be consumed by this group. 

Water that has *safe levels of heavy metals poses no risk.

*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.

Is there a problem with the water supply? 

No. This is not about the chemical quality of the drinking ​water supply but about whether the water has had prolonged contact with metals. ​

Does it matter if I am on public or private water supplies? 

No. Flushing of taps is recommended for all households, including those on public and private water supplies. ​

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 or bath, 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: for example: lead flashing, lead-headed nails, and lead paint. 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 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 500ml of tap water wasteful?

The first 500ml 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:

  1. Contact the environmental health officer at your council offices and ask for the address of a testing laboratory.

  2. Collect the correct sampling containers from the laboratory; a container you have cleaned yourself will not give reliable results.

  3. 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.

  4. Fill the sample bottle almost to the top but without it overflowing.

  5. 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.  You can find a technical fact sheet on Plumbosolvency from the Ministry of Health.​

Page reviewed: 18 Sep 2018 2:58pm