Your clean water guide
Clean water depends on healthy pipes and that means the right products, investment and design says John Fennell.
A healthy plumbing system has to consider everything from design, installation and commissioning to the operation of the system for the entirety of its service life. Plumbing systems that are poorly designed, or where the systems operation has changed over time, can lead to poor quality water.
One of the greatest threats to the quality and longevity of a plumbing system is stagnant water. Allowing stagnant water to develop can generate biofilms in the pipes, potentially allowing the growth of pathogens which are harmful to people. Uncirculated water can accumulate
toxins from chemical absorbed through plastic pipes or heavy metals being leached from metallic pipes over time.
The Plumbing Code of Australia and Australian Standard AS /NZS 3500 set out requirements and guidelines to ensure that these problems do not arise. For other useful design ideas and methods, download the Hydraulic Services Design Guide from http://www.copper.com.au
Design & Installation
The correct design of a plumbing system is key to healthy, high quality performance. During design, dead leg piping should be avoided or restricted to being as short in length as possible. A flushing facility (tap) should be provided where there is low draw-off and fixtures that are seldom used should be placed on flow lines or close to a regularly used service.
Cross-connections of the drinking water supply to other water supplies, such as rainwater or recycled water, is another potential contamination. All water supply systems must be designed and installed so as to prevent contaminants from entering the drinking water supply.
Where there is a possibility of cross-connection, protection is achieved by the installation of backflow prevention devices and air gaps between supply pipework and storage systems. Identification and marking of non-potable water supplies and colour coding of pipework is another way of reducing the chances of contamination. Section 4 of Australian/New Zealand Standard AS/NZS 3500.1 deals with this aspect and must be strictly adhered to.
Correct pipe sizing during design is also crucial. There needs to be sufficient water for all the intended uses, including peak demand, and if the pipe size is too small the water velocity and friction losses will be too great, potentially causing erosion and wearing of the pipes. If the pipes are excessively oversized however, there will be insufficient flow to minimise biofilm build up and settling of silt. AS/NZS 3500.4 which deals with heated water has a section on circulatory heated water systems with information on velocity, temperature and flow rates velocity requirements.
Commissioning & Operation
During commissioning all systems shall be thoroughly flushed out as soon as possible after installation to remove foreign matter and should continue until the water runs completely clear. The system can then be pressure tested in accordance with the relevant regulation.
Water from reticulated systems (municipal water supply) is usually satisfactory for flushing and testing purposes. Where non-disinfected water is to be used for flushing and testing, water shall be disinfected. A procedure for disinfecting water is outlined in AS 4809 and AS/NZS 3500.1.
If more than 8 weeks between installation and full system use is unavoidable:
the system shall be kept completely full and clean water shall be flushed frequently (every 2 weeks) from each fixture until the system is used, or;
the system shall be drained completely and dried out by blowing air through the system, then, if practicable, the piping shall be sealed to prevent intrusion of water and foreign matter.
When the system is connected to the permanent water supply with all taps and valves installed and all draw-off points should be opened until clear water exits the system. This will assist in the development of the protective internal film within the pipe work and draw fresh disinfected water into the system.
In large installations, the flushing should be performed in sections. Multi-storey buildings should be flushed by commencing on the uppermost floor and working down storey by storey.
Water services used to supply drinking water shall be protected against contamination during installation, commissioning and repairs. If any water supply service is exposed to foreign substances or contaminated supply, the service shall be flushed, chlorinated and tested before being placed in service.
After the water system is in operation, special care needs to be given when modification, change in usage patterns or where extensions are added to the systems. The entire system needs to be checked so that all requirements of the Standards and Plumbing Code of Australia are continually being met.
How can copper tube help?
Copper tubing has been the primary material for Australian and New Zealand plumbing for over 50 years. Design information, including the governing standards, are based around copper and copper pipe sizes.
Taking the extra care and consideration when designing, installing, commissioning and operating a plumbing system will improve the quality, performance and life of the system. Of the utmost importance is the profound effect these steps can have on the quality of water being conveyed in a system.
What Are Biofilms?
Biofilms are formed when bacteria adhere to a solid surface and enclose themselves in a sticky polysaccharide (slime).
Biofilms are ubiquitous (ever-present) in the environment. They are formed inside all of our water pipes, toilets, and drains, and, in fact, everywhere there is persistent water.
Biofilms on other surfaces can be scrubbed away, or disrupted using very hot water (steam is best) and concentrated oxidizing agents. However, they will return quickly unless the water source is removed. Hence, there are always biofilms present where, by definition, water is always present (e.g., in the ocean, rivers, our mouths, and our water pipes). It is important to remember when people express concern about biofilms that every drop of water that we drink has been in constant contact with a biofilm.
Biofilms can also become colonised with organisms that may be dangerous to some people. One such pathogen that colonises biofilms is Legionella pneumophila and most isolated cases result from exposure in homes, often from showering in water that passes across Legionella-colonised biofilms. In this case, the best control is to keep hot water temperatures high.
To avoid the risk of scalding, mixing of hot and cold water should be done directly at the tap. While most people do not need to be concerned about Legionnaires’ disease, people with immune system impairment should be aware of this risk. This is why hospitals and nursing homes are of concern.
Using municipal water supply containing a disinfectant helps minimise the formation of biofilms and copper is a natural disinfectant. Legionella cannot survive when in direct contact with copper, however biofilms will continue to increase in all other pipework systems unless treated or removed.
John Fennell is the CEO of the International Copper Association Australia.