Soft Water
is also commonly referred to as aggressive, corrosive, low ph or thin water. This is not strictly true . Soft water is deficient in calcium and magnesium and low in alkalinity. The aggressive water corrodes heating elements, metal fittings such as taps, basin outlets, pipe fittings and heating elements in geysers, dish washers etc.
Causes pipes to rust leaving nasty stains that are almost impossible to remove. This can also be a side effect of previous .. hard water… that has been softened using a salt based water softener.
I’m sure many of us have woken in the middle of the night or early morning to experience the unpleasant effects of a burst geyser that has been rusted through by the water. It sucks to have to climb into a dark , hot roof to attempt to repair. Then try and remove the broken geyser from that confined space and get a new one into position. I empathize with plumbers who do this vital but unpleasant job.
This is what happens when borehole water ph drops and the water which was stable becomes soft and aggressive. This client had galvanised piping throughout his older house , in the walls and foundations and we had to find a solution fast.
Fixing the burst pipe caused by soft water is not so easy but preventing the same happening can be . In the case above the water had very little calcium and magnesium and the water was not prone to precipitation. This was determined by referring to the langelier saturation index for the values of his water. Initially we installed a calcium carbonate based media filter but the water could not absorb enough as it flowed over the surface of the media.
In order to counter that problem it would have meant increasing the media and FRP vessel size to industrial volumes, which would have not been financially viable. Instead we installed a soda ash dosing system which was ph controlled and set to ph8.7 .
Within 3 hours the hardness had increased substantially and within 24 hrs there was no more blue bath. The dense soda ash was almost pure calcium carbonate and we didn’t suffer any precipitation. The system runs 24/7 today and the ph is stable . If the ph changes due to nature then the system adjusts for that automatically. Approximate cost R16 700 ex vat.
One bag of Potash required every 6 weeks at R335 ex vat per bag to counter act the soft water. Nice healthy, mineral and calcium rich drinking water resulted.
But…. that’s not the easiest and cheapest method of countering soft water problems. It has been mentioned in the Limescale section and that is the rust inhibitor system. This method works equally well for aggressive water and hard water.
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