Is Kuala Lumpur Water Hard or Soft? Is it safe to drink?

What is the hardness level of Malaysia water source? 

According to Wikipedia, water is classify as soft water when the hardness is below 60 mg/L, below 60 ppm or below 3.5gpg ( grain per gallon) . 

( Hard/ Soft Calssification Table, Source: Wikipedia - Hard Water )
* Parts per million (ppm) is usually defined as 1 mg/L CaCO3. It is equivalent to mg/L

One recently study on Kuala Lumpur Tap Water in 2007 has shown that most populated areas in Kuala Lumpur are soft water.

(source: A Survey Of Tap Water Quality in Kuala Lumpur - March 2007 ) 

Also commentary of the study has confirmed that piece of finding.

"As shown in figure 3, the hardness of tap water in these20 selected areas ranged from 48 mg CaCO3/L to 92 mgCaCO3/L with an average of 65 mg CaCO3/L. The tapwater in all these areas is considered soft as the hardnesslevel is below 100 mg CaCO3/L. Although there is nohealth-based guideline value, soft water and low pH maycause corrosion of pipes resulting in the presence of certainheavy metals such as cadmium, copper, lead and zinc. Ahardness of 100 mg/L would ensure CaCO3encrustation ofthe mains and very little corrosion"

So, can we drink directly from Tap Water? 

According to Syabas, Tap Water supplied by them is safe to drink. 

(source: Frequently Asked Question - Syabas)

From the same study above, it was concluded that Tap Water in Kuala Lumpur areas is safe to drink but it doesn't represent the entire Malaysia. 

"From the analyses of water samples from 20 selected areasin the Klang Valley, the tap water quality may beconsidered as safe for drinking. Among the 16 parametersstudied for each sample, most of them complied withthe guideline values of the Ministry of Health, Malaysia.The only exception was barium, which was higher than theapproved limit. It is suggested that a special study becommissioned to investigate the reasons for the high concentration of barium in all water samples. However,there is no evidence that barium is carcinogenic and causesadverse health effects at low concentrations.

The survey showed that consumers’ feedback on thesmell, colour, turbidity and taste of the tap water wereacceptable except on certain days. The consumer surveyshowed that 74% of the households used to boil tapwater before drinking. Moreover, 50% of the consumershad water filter fitted to their kitchen supply. It showsthat there is a lack of confidence among the consumersabout the quality of tap water. The result of the survey,however, is not the true representative of the whole ofMalaysia. At the same time, the survey covered asignificant area in and around Kuala Lumpur, in theKlang Valley, covering urban population. In general, theawareness about drinking water quality has increased inthe region, which has been reflected in this work as wellas in a recent report published from south-east Asia(Chung et al. 1997, Kruawal 2005)."

Having to say that, it is also highlighted there are other factors that might affect the water come out from the Tap after it went through the water treatment such as:

• Water disruption / Major Water shutdown
• Piping conditions / broken piping / aging pipe as highlighted in Syabas website

"Q 10 - Why does water supplied to consumers sometimes has occurrences of yellowish/ brownish colour?
A - Although treated water currently complies with all the statutory standards, the residual contents of Aluminium, Iron and Manganese and turbidity value in treated water is still considered high causing it to precipitate in the distribution network at sections of the pipe network where the flow velocities are lower than self-cleansing velocity. Whenever there is a disturbance to the flow in the distribution system like upon opening of supply after a pipe repair, the loose sediments in the pipe gets churned and carried in suspension to the consumers’ taps which explains the discoloration of water observed at the tap. However, this occurs only for a very short period of time until the flow in the system attains its steady state. This also happens in cases where some of the residential area is an old residential area and most probably the piping systems are old and needs to be replaced. Dead end reticulation system or the use of galvanized iron pipes/ storage tanks in the home plumbing system normally will cause water to be yellowish/ brownish. Normally air scouring is conducted by SYABAS at identified locations with similar issues to remove the sediments in the pipelines. If the internal pipes or tanks are old and rusted then they need to be replaced."

• Other factors such as household waterflow network and etc. 

Verdict

As a conclusion, although Water in Kuala Lumpur/ Malaysia is considered as soft water and rated as safe to drink, it is best to invest a water filter system that can actively filter contaminated water to ensure it is safe to drink as there is no guarantee if your water is contaminated due to lack of maintenance and aging pipe( which is quite common in Malaysia. 
It is also best to choose a water filter system that have the following certificates: NSF 42, NSF 53,  NSF 58 (RO), NSF 401.

NSF/ANSI 42 establishes the minimum requirements for the certification of POU/POE filtration systems designed to reduce specific aesthetic or non-health-related contaminants (chlorine, taste, odor and particulates) that may be present in public or private drinking water.

NSF/ANSI 53 establishes the minimum requirements for the certification of POU/POE filtration systems designed to reduce specific health-related contaminants, such as Cryptosporidium, Giardia, lead, volatile organic chemicals (VOCs) and MTBE (methyl tertiary-butyl ether), that may be present in public or private drinking water. The scope of NSF/ANSI 53 includes material safety, structural integrity and health-related contaminant reduction performance claims. The most common technology addressed by this standard is carbon filtration.

NSF/ANSI 58 establishes the minimum requirements for the certification of point-of-use (POU) reverse osmosis systems designed to reduce contaminants that may be present in public or private drinking water.

NSF/ANSI 401 addresses the ability of a water treatment device to remove up to 15 individual contaminants (listed below), which have been identified in published studies as occurring in drinking water. While not a public health issue, the contaminants covered in NSF/ANSI 401 have been detected in drinking water supplies at trace levels and can affect some consumers’ perception of drinking water quality. (NSF/ANSI 401 also applies to reverse osmosis (RO) water treatment.)
* Note: NSF is equavilant to ANSI. e.g. NSF 42 = ANSI 42.

References:

1. https://www.syabas.com.my/consumer/frequently-asked-questions-faqs#q12
2. https://en.wikipedia.org/wiki/Hard_water
3. https://en.wikipedia.org/wiki/Water_softening
4. A Survey of Tap Water Quality in Kuala Lumpur (PDF Download Available). Available from: https://www.researchgate.net/publication/249018418_A_Survey_of_Tap_Water_Quality_in_Kuala_Lumpur. Download PDF
5. http://waterwatchpenang.org/water-facts/
6. http://www.nsf.org/services/by-industry/water-wastewater/residential-water-treatment/residential-drinking-water-treatment-standards