Dealing with blue water
The term blue water is used to describe the pale blue/green discolouration of water that consumers sometimes experience when running their taps or see in the form of similarly-coloured stains on sanitary ware. However, this is not to be confused with the relatively recent incidents involving ‘loo blue’ being siphoned from WC cisterns and being drawn primarily from kitchen taps.
How does this happen?
Research shows that when some newly-installed plumbing systems haven’t been used, but have been left with water within the pipes, the internal bore of the copper pipes can corrode and may start to turn the water blue. This happened in the first lockdown for some who left systems on test.
The other thing that can corrode copper is excessive use of flux, so using the correct type of flux with lead-free solder is important. The older types of fluxes that are based on petroleum jelly tend to solidify within the pipe after the soldering process and don’t tend to be flushed out with cold water alone. They also tend to produce carbon, which when left inside the pipes becomes corrosive. Therefore, making a soldered joint correctly is an important process, not just to be water tight, but to avoid corrosion at a later date.
It’s important to not flux inside the joint, only the outside of the pipe. This is because after you have brightened up the ends and inside of the fitting (use scouring pads and not wire wool as this leaves metal particles behind), when the joint is pushed back together the excess flux slides back along the joint and won’t ooze inside the pipe.
Blockages
Where flux can’t be washed out, for instance within a gas supply, any excess flux actually becomes a restriction or blockage. In cold water, the excess flux may block the tap and other filters or the orifice within the float valves, which just makes the commissioning a lot harder to get rid of it. This might lead to the system requiring chlorination, which isn’t something a lot of people are suitably qualified to do, and more expense.
If a system is not going to be used, for example if the occupiers are not ready to move in or may be away for some time, then draining down the system will help stop the corrosion of the copper. This is even more important in soft water areas as the water is more corrosive than those in hard water areas.
Softened water has been known to cause pitting in some cases and corrodes copper tube. It’s not unusual to find green speckles on the outside of the tube. Don’t wipe these off, as the pipe will almost certainly start to leak. The green speckles are pitting from corrosion. If this is visible then the system is badly corroded and will need replacing as it won’t be in just one place.
You should read the labels on the side of the flux you purchase to ensure you are using the correct type. Cleaning off the joints afterwards is very important as the residue is corrosive. Residue can lead to joint failures some time down the line.
Useful information
• On the Water Regulations UK website, under Publications, installers can find the Water Industry Approved Installation Methods specifically relating to solders and fluxes (WRAS 9-04-02 Use of solders and fluxes).
• Make sure you have good ventilation from the fumes as they are known to be causes of lung cancer. See the latest update from the HSE on welding fumes/COSHH regulations on the HSE website.
• Soluble fluxes will be flushed out as part of the commissioning process. Again, the Water Regulations UK website information leaflets set out some excellent information on commissioning plumbing systems (9-05-01 Commissioning plumbing system).
APPROVED PRODUCTS
Below are the links for various approvals websites:
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