How to Keep Your Water Safe

Since water in Flint, MI, was found to contain lead, the issue of what’s in tap water has been in the spotlight. Recently, researchers suggested that faucet-mounted water filters given to Flint residents may actually increase the amount of bacteria in the water.
Meanwhile, some residents of Corpus Christi, TX, are being cautioned not to use their tap water for any reason after possible contamination by an industrial chemical. Even boiling the water will not render it safe, officials said.
How effective are water filters and can they help in any situation? WebMD turned to Ken Spaeth, MD, MPH, chief of occupational and environmental medicine at Northwell Health, Great Neck, NY, to talk about water quality concerns. We also spoke to Nancy G. Love, PhD, professor of civil and environmental engineering at the University of Michigan and a researcher who studied the issue in Flint, about water filters and bacteria.

 What is the benefit of having a water filter?

If there is a concern, belief or evidence that there are contaminants of any kind in the water that could pose a health risk, having a filtration system capable of removing those contaminants is clearly a preventive measure one could take.
There is a wide range of water filters and water filtration systems and also a wide range of what they can and can’t do. This is yet another instance where consumers have to educate themselves.

In general, what can a water filter do?

Some are better at filtering chemical contaminants. Some are more effective at [filtering] microbes such as bacteria, viruses or parasites. Some do both.But there are literally thousands of chemicals and hundreds if not thousands of bacteria, parasites and viruses and heavy metals. So the extent they are effective depends on the individual filtration system.

What’s the best way to shop for a water filter?

Step one is, what is your concern? What is in the water or might be in the water that is raising the concern? The easiest way and probably the most effective is to track down a copy of a recent quality report from the local water authorities. Look at it and see if there are contaminants that exceed the EPA standard. Based on the answer, one can think about ways to address those issues.
Which filter system you use depends on a lot of factors [in addition to which contaminants you are trying to filter].  How extensive do you need—a faucet, multiple faucets, showers, sinks?
Look for third party certification from what is being claimed by the manufacturer or retailer. Typically this means you will be looking for certification from organizations such as the National Sanitation Foundation or UL.
And what’s the budget? The less expensive are the pitcher filtration. But not all are capable of filtering out a lot of different kinds of contaminants. The higher end [systems] would be filtration systems that plumbers install.

Can bacteria from municipal tap water be harmful?

In most instances the presence of bacteria is not an issue, but there can be situations where it can become an issue. The water monitoring [done by municipalities] would typically be identifying the presence of bacteria.
There have been instances of shigella, an infectious bacterial agent [causing diarrheal disease]. Legionella [linked with Legionnaires’, a serious respiratory disease] has been traced back to sources of water. Those are certainly two of the most common ones.
It’s very unusual to have harmful bacterial concerns in municipal water supplies.

Is there anything you can do to kill the harmful bacteria from drinking water?

Typically, you would have to boil your water to be sure that would not be an issue. If you do it 5 to 10 minutes that would be enough.

What’s the best way to clean a faucet-mounted water filter?

You don’t clean a filter cartridge. You replace. The manufacturer recommends replacing about every 100 gallons. The increase in counts starts in two weeks, in our studies. If you do the flushing you remove most bacteria.

Does bacteria build up in all water filters?

These [the ones used in Flint] are the ones that screw on your faucet, I think the most common kind. They are made of activated carbon which will absorb chemicals from the water. The key thing about the filter media is that it is held together with a polymer that has very small pore spaces. So particles will typically not get through these filters. They are also certified for lead.
There are bacteria in all distributed water. Because these are present, when you put in a filter that has a pore space smaller than the bacteria, the bacteria will get caught in the filter. At the same time the filter is removing chemicals from the water and the bacteria can grow on some of those chemicals.
When the filter is off and moist, they grow. [The filter also] takes out the chlorine, which is the disinfectant that would normally kill the bacteria. We don’t know if they are bad organisms; we are still studying that.

What kind of bacteria build up in these filters?

That is what we are looking at. That takes a lot of analytical experiments.

Can you minimize bacteria in the filters?

Yes. When you turn on the faucet first thing in the morning, bypass the filter. Turn off the knob. Then you are not loading the bacteria that grew overnight. Let it go for a couple of minutes. Once you turn the filter back on, let that first minute of water go down the drain. That will help a lot.

Should consumers test their water at home?

I don’t think it needs to be done routinely. In a given situation, if there are specific concerns, if a quality report indicates there may be contamination in a local water supply — if there are legitimate reasons to have concerns — it’s an option.
There are labs that will do it. In some states, public health labs will do it. Commercial labs are also willing to do it.
It’s not always so easy to do. Typically, it requires money. You have to pay in most settings. You have to know what you are testing for. You can’t just send off a sample and say, “Test my water.”
You can still get home kits, but they are qualitative — they don’t give you levels. They will give you an indicator of what is present — kind of a yes [or] no.

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