Explained: Main reasons why your water is corrosive

Cathal Walsh
Environmental Blogger

Friday, 5th April 2019

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Pipe leaking with water pouring out of it

The problem: Corrosive water is probably one of the most common problems in drinking water. Many have learned this the hard way when they have found pin hole leaks emerge in their pipework and fittings. Leaks like these can cause a lot of damage to buildings, especially when they start upstairs or in the attic. You may also see extensive damage to the inside of your radiator, and the pipes surrounding it if you have corrosive water. For this reason you may also find that when looking at your immersion heating , the copper cylinder is burnt out, or has holes in the surrounding pipes. It is true that corrosive water can cause damage to your household plumbing in a variety of ways.

The tendency of water to cause corrosion or scale in pipes and fittings is measured using a useful scale known as the Langelier Saturation Index (LSI).

Water with a negative Langelier Saturation Index proves to be corrosive. Corrosiveness in water can cause a range of problems, especially for those with metal pipes. A large problem is that in many houses, especially old houses, the whole plumbing system is made up of a network of metal pipes. Often the homeowner may not know that the water is corrosive and the damage goes under the radar. Corrosiveness in water often results in pinhole leaks appearing in metal pipes. These holes then get larger and larger.

This can be a particular problem where a leak starts when a family goes on holidays or leaves their home for an extended period of time and returns to find their whole house flooded as a result of these leaks finally bursting a pipe.

There are also a number of health concerns that occur as a result of corrosiveness in water. The main one is again a result of corrosiveness and its reaction to metal pipes.

When corrosive water comes into contact with copper, it dissolves some of the copper into the water. This results in blueish- green stains around some fixtures in the house. It can also be ingested into the human body if someone drinks this corrosive water. Excess copper in the human body can cause stomach and intestinal distress such as nausea, vomiting, diarrhoea and stomach cramps.

Corrosive water may also dissolve any lead it comes into contact with into the water. Lead is a cumulative poison that can severely affect the central nervous system. The world health organisation (WHO) has warned that the ingestion of lead through drinking water has been shown to have an adverse effect on the health of the individual.

About the index:

The Langelier Index is one of several tools used by water operators for stabilizing water to control both internal corrosion and the deposition of scale. Water supply operators can optimize their water supply systems and identify leakage potentials with the Langelier Index

This index was made to calculate the level of saturation of calcium carbonate in water. The level of calcium carbonate saturation should be as close as possible to 0.0 LSI, generally though this is hard to achieve so an index of 0.0 + or – 0.3 is normally an acceptable index.

A negative LSI means that the water is under saturated, this leads to the possibility of corrosion. A positive LSI however means that the water is oversaturated, this could lead to scaling in the water.

Not only does water with a negative index (corrosive) pose the risk of leakages in the water source, it also can pose a health threat to those consuming the water as corrosive water may dissolve enough metals in its travels to the consumer (e.g. copper and lead) that it may then be deemed unsafe for human consumption.

The Langelier Saturation Index consists of 6 variables: