Water is a resource that can be taken for granted in the developed world. Ubiquitous access to clean water makes it easy to forget that a great deal of thought goes into ensuring that our water is fit to drink.
According to Richard Bolton, marketing manager at press-connection manufacturer Viega, those responsible for commissioning drinking-water systems for buildings need to consider a wide range of factors.
First, it is important to select the right pipes and fittings.
Materials can be copper, stainless steel or multilayer composite pipe, and each has its advantages and disadvantages.
“With copper, it is very inert and non-permeable,” Mr Bolton says, “meaning it does not absorb anything it comes into contact with. Additionally, installers are familiar with it”.
While stainless steel is even more inert and is highly resistant to corrosion, it is harder to shape.
Copper and stainless steel pipe are ideal solutions for projects that require fewer fixing points along the pipe length or where improved resistance to fire is an advantage.
Multilayer composite pipe, meanwhile, is cheap and flexible – it can achieve complex routing around voids and obstacles within buildings, fit into tight spaces, and accommodates long runs where minimal joints are required.
“However, it can be susceptible to heat, and some types of plastic pipe can leach chemicals that contaminate water,” Mr Bolton says.
As a result, when selecting materials, thought needs to be put into what a building will be used for.
“On houses, many installers favour plastic because it’s easy, quick and cheap,” he says.
“Press connections simply require a press gun, which provides consistent force on every connection that you do”
Richard Bolton, Viega
“If you’re doing a job on a prominent building, however, you would favour stainless steel and that is certainly the case for healthcare facilities because it’s essential to keep contamination to an absolute minimum.”
The type of fitting can also have a significant impact on potential contamination, leakage or inconsistency. The main options include soldered joints, compression fittings, flange fittings and solvent welded.
“You don’t want solvent coming into contact with drinking-water system, and with solder you have to use heat, so there may be flux or swarf or other debris that can also contaminate, and there is also a risk of fire,” he says.
“Compression is clean but relies simply on the plumber’s muscle to connect the pipe together, so there is no consistency in the strength of the joints. It may hold during testing only to begin leaking when the building is complete and occupied – resulting in the need for costly remedial work. There can be similar issues with flange fittings.”
As a result, the method favoured by Viega is press connection. “With press connections, you do away with all of those issues,” Mr Bolton says.
“Press connections simply require a press gun, which provides consistent force on every connection that you do.
“Designed with a double pressing both before and after the compression, it ensures a permanent seal that will withstand both torsional and longitudinal forces.”
Another issue to consider is how materials are supplied. The products may be certified as safe for use on drinking-water systems, but if they aren’t packaged or handled correctly from the point of manufacture, there is a danger of contamination.
“For example, wet leakage tests during manufacture can introduce bacteria that can be difficult to eliminate, especially if the conditions the products are stored in allow the bacteria to grow,” he says.
“A warm environment will enable bacteria such as pseudomonas aeruginosa to thrive as the optimal breeding temperature range is between 25 deg C and 45 deg C. It is always recommended that specifiers look at the product details and select systems that have been dry-tested during manufacture.
“Also, while on site, the pipe, fittings and other components must be kept in a hygienic space to avoid accidental introduction of dirt and contaminants.”
Great attention should also be paid to the design of the pipework.
“With drinking-water systems, there are some golden rules,” he says, adding that it is critical to avoid ‘dead legs’ – parts of the system where water remains static for a significant amount of time.
Considering building usage
“You need to think about how the building is going to be used,” he says. “A school can sit for six weeks in the summer with water in the pipes going nowhere. Hotels can have similar issues.
“If you have stagnation, and especially if you add heat to that, it accelerates the risk of microbiological contamination.”
And that has the potential to be disastrous.
“If this happens, you will need to clean out the system and undertake close monitoring and often lengthy remedial works, which leads to disruption and adds costs,” says Mr Bolton.
“However, these issues can be avoided by designing the potable water system according to best practice, choosing the correct materials and ensuring contamination is prevented both during and after installation.”
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