Wednesday, August 03, 2011

Testing your drinking water - the whys and why nots

I have been receiving requests to find out more about sending drinking or filtered water for lab testing - how, why, where etc. so I have compiled a short advisory here for those interested readers out there.

Some queries are linked to the use of water filters in the home e.g. filtered water actually makes the children sick. Dear readers, for goodness sake, if you think that filtered water is making your children, just disconnect the water filter and drink tap water straight or boiled. Our tap water is supposed to strictly follow WHO's drinking water guidelines.

You are strongly urged to read through my earlier posts on water filters to get a have a better background of this post.

This is probably the most important question to answer in order to justify testing your drinking water. In most cases, the user suspects that the tap or filtered water is causing health problems in the household. At this point, it will be good to be specific about your health problem and do some research to find out exactly what substance in the water can be causing that problem. E.g. gastrointestinal discomfort? Then that could be caused by bacteria in the water.

Most people say that they want to send their water samples to a commercial laboratory for analysis. But analysis is a BIG word because the laboratory will then ask them, "what components in water do you want to analyse?" This is the point when most users will leave their mouths hanging. You see, there are tens of thousands of chemicals in use today and probably several different methods to analyse each of them. Even WHO's guidelines go up to more than a hundred water parameters. It is simply not economical to analyse for so many components unless you own the water utilities company. And in general, laboratory testing is not cheap - each additional parameter to test heaps on additional cost.

Ideally, you should have answered the "why" question reasonably well so that you have a good idea of what chemicals or parameters to test for. Personally, I feel that coliform or E. coli should be a good test to start with as it gives you an idea of the level of human contamination in the water. The presence of coliform or E. coli should reflect a high likelihood of other human pathogens in the water. Other potential candidates to be tested for include chlorine, fluoride, heavy metals e.g. lead, pesticides though it really depends on your particular situation.

Figure: Testing for coliforms using the membrane filtration method

Figure: Testing for coliforms using the most probable number (MPN) method

There are no lack of commercial testing labs in Singapore though they serve commercial clients most of the time. Do call them up to get a quote for testing your water according to the parameters you specified. Typically, they require a water sample to be sent over to their lab. And if you want to be scientific about it, you may to perform replication in your testing i.e. testing more than 1 sample. Some of the better known testing labs are Tuv Sud PSB, SGS Testing, Setsco Services, CPG Laboratories (a newcomer).

And if you get an "ND" in your testing report, it means "not detected". It would be smart to ask the lab what kind of detection limit (DL) does their testing method involve because ND doesn't mean something is not there or means that the water is safe. ND simply means that that particular could be present but below the detection limit  (BDL). Better still, ask the lab about the level of certainty of your results e.g. +- 5% or +-0.1ppm (parts per million). Professionals will normally know the answers to the above questions.

Interpretation of your test results could be the hardest part of the whole process. Most times, the lab is not qualified to interpret your results and tell you how safe your water is. You should always check against WHO's guidelines and PUB's typical values. But as mentioned in an earlier post, WHO's guidelines are not omnipotent. Therefore, you could be on your own to decide how safe your water is. In the case of water filters, the interpretation could be simplied by testing both the influent and effluent of your filter. E.g. if you filter is supposed to remove bacteria and yet more bacteria is showing up in your filtered water (effluent), suspect that your filter is failing you.

Final thoughts
I know... water testing is a big and sometimes formidable topic but I hope this post has clarified some of the points. I am always a staunch supporter of consumer education so please find out all you can about water testing, ask the right questions and hopefully make the right choice. Good luck.


Superbguy said...

This is a very useful post. Thanks for this.

I have a question. The water in the common bathroom often stinks. When I turn the tap on, a foul odour spreads in the bathroom and it is quite difficult to shower in the bathroom. What kind of testing would you recommend? Or would the testing labs know about this?

CK said...

Have you tried calling your utility company about this? I am sure this is something they are willing to rectify or at least advise you about.