How much should I fear tap water with turbidity levels of 1.7 ntu?

November 30, 2018 9:10 AM

Water company has issued a boil-water notice for my area, which reads, in part: Water samples taken on November 29, 2018 had turbidity levels of 1.7 ntu, which is above the regulatory standard. Because of these high levels of turbidity, there is an increased chance that the water might contain disease-causing organisms. Some quick research shows that European standards allow turbidity up to 4, so do I need to boil everything?
posted by qldaddy to Home & Garden (5 answers total)

If you don't have a water filter that is rated to deal with this kind of thing, yes, you should. Any water that you drink or prepare food with, at a minimum.

Here in Milwaukee, in 1993, we had a nasty outbreak of Cryptosporidium and it is really nothing to play around with. If your water company has measured an unexpected increase in turbidity, this could be harmless, but as noted, it does correlate with a higher potential for nasty little micro-organisms.

I installed a decent reverse osmosis filter and tank and all of the water we drink or cook with is highly filtered. Because the city's water has been cleaner than average since the whole crypto thing, I find I don't need to change the carbon filters anywhere near as often as many other people do.
posted by jgreco at 9:34 AM on November 30, 2018

Personally I'd get some bottled water for drinking and continue to use tap for cooking and washing.

Here in the UK, the standard limits are 4 NTU at consumers' tap. 1 NTU at water treatment works. So if they took your measurements at the treatment plant / source then could breach limits here too.
posted by JonB at 9:44 AM on November 30, 2018

Turbidity is a simple test that measures how cloudy a sample is. It does not necessarily mean that your water is harmful, but it does indicate that there is an issue that *could* indicate contamination (bacteriological, chemical, or physical). Without other tests, you just don't know. It is used as a quick and easy measure of water quality. The water company is most likely doing further testing (the kind that takes days, not minutes). In the mean time, I would take the notice seriously.
posted by jraz at 9:48 AM on November 30, 2018 [4 favorites]

Oops, forgot to say.

If it were me (I work at a drinking water lab), I would use bottled water. The water utility may already know the source of the issue and has determined it to be biological/microbiological in nature. But depending on the type of contamination, boiling water can actually make the problem worse (it concentrates the contaminant).
posted by jraz at 9:57 AM on November 30, 2018 [5 favorites]

It's possible that a higher NTU standard is matched with a higher PPM of chlorine or other disinfectant. So while the 4NTU maybe considered safe in other areas it may only be because the water also contains more chlorine.
posted by Mitheral at 12:55 PM on December 1, 2018