Wednesday, January 20, 2016

Ok, water from the water treatment plant is clean... do I still need water filters?

Dear CK,

I have read below 2 articles with great interest and I like your logical reasoning very much.

I understand that water level in Singapore is clean and that PUB has exceeded WHO guidelines. However, I have one further question in regards to the need of water filter for home.

The water is clean at PUB treatment plant. But the water will need to pass through the pipes before reaching our home. We do not know when was main pipe in the ground was last changed? For sure, the small pipe leading to our home is as old as the building which we live in.

Please note that I am not affiliated with any water filter companies. I just want to learn more as I am thinking of purchasing a water filter system to clean the water at final stage before boiling and drinking.

I look forward to your advice. Thank you very much.

Best Regards,

Dear KH,

Thank you for enjoying my writing style. I always prefer to keep things simple, straight to the point and free of unnecessary technical jargon, with some humour (dark or otherwise) thrown in if possible. Naturally, some technical terms are unavoidable since water itself is a technical subject.

You are absolutely right. Water straight out of water treatment plants is definitely within specs. The question is what happens in between the outlet of the plant and faucet in your house? We are talking about miles and miles of piping, pumps, valves, tanks.

And if you look at the figure below, we are also talking about third parties like town councils and building management committees  (BMC) sharing in the responsibility of providing you with nice, clean water. (Also, note where the responsibility of one party ends and the other begins.)


Anyway, the same question has been raised before in the media in Jul 2009. Do go through it as some interesting points had been put forth, accompanied by equally interesting answers from PUB, a concerned expatriate, a doctor and others.

  1. In case you did no go through the above articles, I will summarise their contents here. In a nutshell, yes, contaminants can enter your tap water along its tortuous journey. Assuming PUB is doing its job well of maintaining its extensive distribution network (no reason to assume otherwise), it boils down to how well your town council or BMC is doing its job in maintaining its piping and tanks.
  2. Barring unexpected incidents like finding a dead maid in the water tank, by regulation:
    Management corporations and town councils must engage a licensed water service plumber at least once a year to inspect and, where necessary, clean and disinfect their water tanks and certify that the tanks are fit for drinking water storage."
  3. The most common culprit in your tap water is rust (an iron compound by the way) silt. It comes from the corrosion of iron piping, especially older piping. It can be visible in water or seen on your filter elements. PUB maintains that this is harmless.
  4. The recommendation is to run your tap till the water becomes clear. Then you take that water for consumption. (Whatever the case, whether iron or other contaminants, this is my recommendation too! Especially in the morning when water has remained stagnant in your piping for long hours during the night. Stuff, if any, from your pipes tend to leach into your water during this time.)
  5. Finally, though the last portion of the water distribution system is not under PUB's jurisdiction, you can call it up if you suspect anything amiss in your tap water.

Regarding the last point, PUB will typically send a technician down to take a sample of your tap water back for testing. The test result will come back as either the water is in compliance or out of specs. Don't expect to see what water quality tests have been conducted and certainly don't expect to be shown the test data.

Still, if the water is out of specs, I believe PUB will then bring pressure down on your town council or BMC to better on the ball on its maintenance programme. Either way, you are safe. Do you still need a water filter then?

Remember the rusty silt that makes your water look "dirty"? Yeah, it is supposed to be safe. Meaning no one, including your town council, will be doing anything about it. Iron (or rust) can be bothersome because it can impart a metallic (or bloody taste at higher concentration) taste. Another problem of iron/rust is it can stain clothes, walls, floors. What colour of stain? Think of rust - orange, red, brown and any colour in between. 

Notice the orangey stuff inside the pipe - that is the tell tale sign of iron. Yup, it is a form of rust. They usually arise from cast iron or galvanised pipes.

If it bothers you (it BOTHERS me), by all means, get a filter to remove it. Nothing fanciful, a cloth filter can do the job. Or if you want something more reliable and can afford the space, get a 10-inch sediment filter rated for 10 microns or less. The rating tells you the maximum size of a particle that can go through i.e. anything more than 10 microns will not pass through the filter.

Figure: A 10-inch 5-micron pleated filter used for experimentation

So far, I am only talking about iron in water. Piping can impart other less desirable and far less benign pollutants into your drinking water. This is usually true in older piping before people became enlightened about the dangers of various materials in drinking water.

  1. Case in point - lead. Commonly used in old piping networks in solder at the joints. Hong Kong has an interesting case - "Water pipes of thousands of flats in Hong Kong will have to be replaced after initial tests revealed excessive levels of lead in the water of a two-year-old public housing estate in Kowloon." Yup, the year was 2015 and the housing was only 2 years old. The blame was placed on the plumbers (and later the contractors) who used substandard materials containing lead solder (banned in HK) from China.

    As a follow-up to the HK story, attention then turned to
    Singapore as one of the contractors (China State Construction) was also involved in some projects here. Rising to the occasion, PUB categorically replied, "Lead or lead alloy, and water fittings made of lead or lead alloy, including soldering joints with lead content are not allowed for use in potable water supply systems in Singapore"

    Results of lead poisoning are well known. As a neurotoxin, it causes mental retardation. Children are especially vulnerable, leading to learning difficulties and delays in development. Unfortunately, lead can come from the food we eat (e.g. adulterated medicines) and the air we breathe (e.g. lead dust from leaded paint).
  2. Asbestos. This was formerly used in cement piping for reinforcement. Over time, as the cement pipe undergoes wear and tear, the asbestos fibres can end up in the water. Though inhalation of asbestos is the most common route of entry, evidence suggests that cancers in the esophagus, larynx, oral cavity, stomach, colon and kidney may be caused by ingesting asbestos.

    I can't really find any data on the usage of such piping in Singapore. If anyone has any information, please let me know.
  3. Copper. Possibly from copper pipes. The copper corrodes over time into water. Bluish green stains are signs of copper in water. Less of a health concern unless the concentration is high. You can sometimes see the same coloration on the exterior of copper pipes because the copper has reacted with substances in air.

Wednesday, January 06, 2016

Stuff that you should know about UV treatment of drinking water

Happy New Year to you !

I would like to check if you have heard about Tami Water system - Strauss Water.? Searching through your blog, I could find topics on UV treated water.

Would like to hear your professional opinion about UV sterilize water treatment, is it necessary in Singapore ? prolong exposure to UV treated water is it safe?

The BB system you mentioned looks a bit bulky for most kitchen top though I really like stainless steel products. Looking for a convenient and safe water filtration system.

Sorry I don't know how to pose questions via your blog.

Thank You and Best Regards,


Hi R,

Personally, I do not see the need for a water filter for Singapore tap water. The water is already quite clean so any filter will be hard pressed to clean it further. (See this post and others in the filter/purifier tag.) Unless you suspect your pipelines and/or water tank are somehow contaminated. Still, it will be easier to call your residential management to take care of it. Or unless you have a medical condition that requires very clean water to be consistently provided.

A small note on water parlance: "sterilisation" means the destruction of all microbes while "disinfection" means the significant reduction of microbes. Water is normally "disinfected" to make it safe for drinking. It is not practical and necessary to sterilise water for drinking. Sterilisation is usually done in medical applications (e.g. sterilising surgical tools), microbiological setting (e.g. incubation for bacterial count) or pharmaceutical manufacturing.

As for UV (ultraviolet) treatment of water for drinking, you probably have already guessed my opinion that it is similarly not necessary for Singapore tap water.

How does UV work?
UV disinfects by disrupting the DNA in microbes (aka bugs). If the DNA is sufficiently damaged (enough contact time or UV power or both), the microbe cannot repair that damage and its bodily functions will be affected, leading to a halt in reproduction or death.

In case anyone thinks I am against UV, let me proclaim that I am a fan of UV treatment in the situations that it is necessary. Its main advantage is it is a relatively simple system to operate. You just need to plug into a power supply and you are good to go. No messy chemicals to resupply, no need to calculate dosage of chemicals and no chemical waste to fuss over its disposal. UV can work under any temperature and pH. These are two master parameters which will invariably affect any water treatment involving chemical reactions. You do not need to worry over the undesirable generation of disinfection by-products (DBPs) including potentially carcinogenic chloroform in the case of chlorination.

Even though UV treatment has been worded as "UV radiation" or "UV irradiation", there is absolutely no ionising radiation (e.g. X-rays) involved so no way will your water become radioactive. UV is generally safe for water disinfection.

Remember the bugs you killed or injured by UV earlier. Though they can no longer reproduce, their dead and dying cells are still in the water. There is some concern these cells can be pyrogenic (fever causing) or become food for other bacteria further downstream. Nevertheless, unless your dead/dying cell count is very high, I believe this should not be an issue.

Of course, you have to be aware of UV's limitations as well. UV is only for disinfection of bugs in your water. It does not remove metals, pesticides, solvents and other chemical substances. (Admittedly, UV does destroy certain organic compounds but most UV units are not designed for this function. Even those experimental ones designed for this function are usually combined with other methods e.g. ozonation, addition of hydrogen peroxide.)

UV also does not leave any residual in the water after treatment. Let's say chlorination - it leaves chlorine residuals in the water long after leaving the water treatment plant. Enough to last till the water comes out of your tap. In between treatment and your tap, the residuals prevent recontamination by microbes as the water flows through pipes, pumps, valves and whatnot. Not so for UV, your water is on its own after UV treatment unless you intentionally add chemicals e.g. chlorine, chloramines, for that purpose. (Hmmm.... that kind of defeats the purpose of using UV, doesn't it?)

One big challenge of using UV is your inflowing water has to be very clear (turbidity of  less than 1 NTU for the techies out there). If your water contains solids e.g. clay, sediment, the bugs will hide behind these solids and receive shielding from the full power of your UV light.

Yes, you do not have to resupply chemicals in UV treatment BUT you have to replace the UV lamp periodically as it will lose its power over time.

Finally, the lamp may be fouled over usage. Grime, dirt, debris can stick to the lamp and these stuff prevents your UV light from shining out effectively. Cleaning then becomes an important part of maintenance. Industrial UV setups usually have their lamps protected by removable sleeves. Even then, the sleeves themselves can be fouled and thus have to be cleaned as well.

End of UV talk

Tami Water, Strauss Water... No, I haven't heard of them but I made a quick search and took a look at their webpages. They seemed like an aesthetically packaged water filter (carbon blocks + UV) that can provide both hot and cold water. As I said earlier, you don't really need water filters in Singapore. Unless you are interested in their hot/cold water combo function. But looking at the price (S$1200 for the Tami Primo model), I don't think that is the most efficient use of your money.

If you really must get a water filter, Arkwater does provide one in stainless steel housing a Doulton ceramic filter. It is pretty slim and designed for countertop use. (Let me stress that I do not derive any benefits from the sale of their products.)

Figure: My trusty Steripen portable UV water treatment unit. Note the UV lamp on the left end.

Figure: Disinfection in action. Notice the bluish light at the lamp. It is supposedly safe for the eyes as the UV cannot escape from the water surface. It takes 1 minute to disinfect 0.5L of clear water. If your source water is murky, it pays to at least sieve your water through a clean piece of cloth or coffee filter before going to UV.