Does lead float in water?
Quick answer: No, lead does not float in water. As a dense metal, lead sinks. The real concern is that lead dissolves into water as it passes through lead-containing plumbing materials, making it invisible and undetectable by sight, smell or taste. Australian drinking water guidelines set a health-based guideline value of 0.005 mg/L for lead in drinking water.
Why lead does not float in water
Lead is one of the densest common metals, with a density of approximately 11.3 grams per cubic centimetre. Water has a density of 1.0 g/cm3. For an object to float, it needs to be less dense than the liquid it is placed in. Because lead is roughly eleven times denser than water, a piece of lead placed in water sinks immediately.
The more important question for households is not whether lead floats, but whether lead dissolves into water. It does. Lead is a soluble metal under certain water chemistry conditions, and when it leaches from plumbing materials it becomes part of the water itself, invisible to the eye and undetectable without testing.
How lead gets into tap water
Lead enters drinking water primarily through contact with lead-containing plumbing materials, not from the water source itself. Older homes, fittings, solder joints and service lines can all contribute lead to the water that flows through them, particularly when water sits in pipes for extended periods.
According to the Australian Drinking Water Guidelines, a review found several Australian and international studies that detected up to 0.162 mg/L of lead in drinking water due to leaching from lead-containing plumbing materials including taps and lead service lines, suggesting that leaching from lead-containing plumbing materials can be substantial.
The same guidelines note that in major Australian reticulated drinking water supplies, total lead concentrations can vary in range, with typical concentrations less than 0.005 mg/L. This means the water leaving a treatment plant is generally within guideline limits, but concentrations can rise as water travels through household plumbing.
What Australian guidelines say about lead in drinking water
The Australian Drinking Water Guidelines state that, based on health considerations, the concentration of lead in drinking water should not exceed 0.005 mg/L. This guideline value is based on attaining a blood lead concentration attributable to drinking water of up to 1 microgram per decilitre in children between 6 months and 2 years, using IEUBK modelled data.
Australia's guideline of 0.005 mg/L aligns with international direction. The Australian Drinking Water Guidelines also note that the European Union has recently issued a revised drinking water limit for lead of 0.005 mg/L, to be implemented by 2036.
For context, a California public health goal of 0.0002 mg/L was reviewed but, as the Australian Drinking Water Guidelines note, was not considered feasible or appropriate for the Australian context.
Practical steps households can take
Because lead enters water through plumbing contact rather than the source water itself, simple habits can help reduce exposure. NSW Health notes that the Environmental Health Standing Committee (enHealth) recommends flushing cold water taps used for drinking and cooking for about 10 seconds first thing in the morning to draw fresh water through the tap.
This is particularly relevant for water that has been sitting in pipes overnight, when leaching from fittings has had the most time to occur. Using cold water rather than hot for drinking and cooking is also commonly recommended, as hot water tends to dissolve metals from plumbing more readily than cold water.
Households in older properties, or those with older tapware and fittings, may wish to have their water tested by a laboratory to understand their actual lead levels.
Lead in water and filtration
Because dissolved lead is invisible and has no taste or odour, some households choose point-of-use filtration as an additional measure. The Evolved H2O HydroX Electric Water Filter reduces lead by more than 99.89% (tested reduction). The Evolved H2O 3.5L Glass Water Filter Jug reduces lead by 99.5%.
Key takeaways
- Lead does not float in water. It sinks, and more importantly, it can dissolve into water from plumbing materials.
- The Australian Drinking Water Guidelines set a health-based guideline value of 0.005 mg/L for lead in drinking water.
- Typical concentrations in major Australian reticulated supplies are less than 0.005 mg/L, but leaching from household plumbing can raise levels substantially.
- Flushing cold taps for around 10 seconds in the morning is a simple, practical step recommended by enHealth.
- Households in older properties may benefit from laboratory water testing to understand their actual lead levels.
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Frequently Asked Questions
Does lead float in water?
No. Lead is approximately eleven times denser than water, so it sinks. The real concern is that lead can dissolve into water as it passes through lead-containing plumbing materials, making it invisible and undetectable without laboratory testing.
How does lead get into tap water?
Lead enters tap water primarily through leaching from lead-containing plumbing materials such as older pipes, solder joints, taps and service lines. The Australian Drinking Water Guidelines note that leaching from these materials can be substantial, with some studies detecting up to 0.162 mg/L in affected supplies.
What is the Australian guideline for lead in drinking water?
The Australian Drinking Water Guidelines state that, based on health considerations, lead in drinking water should not exceed 0.005 mg/L. This figure is based on modelled data for children aged 6 months to 2 years and aligns with the European Union's revised limit of 0.005 mg/L, to be implemented by 2036.
Can I tell if my water contains lead by looking at it?
No. Dissolved lead has no colour, taste or odour. The only reliable way to know whether your water contains lead above guideline levels is to have it tested by an accredited laboratory. This is particularly relevant for households in older properties with older tapware or plumbing fittings.
What is a simple step to reduce lead exposure from tap water?
NSW Health notes that enHealth recommends flushing cold water taps used for drinking and cooking for about 10 seconds first thing in the morning. This draws fresh water through the tap and reduces the concentration of lead that may have leached from fittings while water was sitting overnight.
Does boiling water remove lead?
No. Boiling water does not reduce dissolved lead. In fact, boiling reduces water volume through evaporation, which can concentrate dissolved metals including lead. Boiling is effective against some biological concerns but is not a method for addressing dissolved metals in drinking water.
