A number of factors can cause plumbing pipes to corrode, but a common factor is joining plumbing parts made from different plumbing metals. While professional plumbers know to avoid this, householders who fix their own pipes or do DIY plumbing jobs may not be aware of the risks of joining dissimilar plumbing metals.
The Risks of joining dissimilar plumbing metals
In any plumbing system, pipes and joints should always be of the same material. When parts made from different metals are used, the result is usually corrosion. Corrosion can occur much more quickly than expected. Corrosion can lead to brittle pipes and complete breakage or disintegration if the problem is left unaddressed for long enough.
Brittle or broken pipes can, in turn, lead to leakage, flooding and water damage in the home. In industry or manufacturing applications, the mixing of dissimilar metals can cause equipment to break down very quickly.
Galvanic corrosion – also known as dissimilar metal corrosion – is caused by an electrochemical process that occurs when different metals come together in a damp or wet environment. The corrosion is caused by an electrochemical reaction, which can lead to rust and clogging in steel parts where they are used. The water running through the pipes acts as an electrolyte that sparks the corrosion.
Corrosion can appear anywhere in the plumbing system. It could result in the areas where screws and pipes come into contact, or it could result where two separate sections (made from different metals) of a pipe connect.
The area where fixtures come into contact with pipes can also experience corrosion. The extent to which corrosion occurs and the speed at which it occurs may also be affected by the environment. A damper environment with no temperature control could lead to more rapid corrosion when certain dissimilar metals are used together.
You can avoid corrosion by seeking advice from a licensed plumber before making changes to your plumbing system. If you are replacing a joint or some other part in your pipes, make sure that you use the same metals for connections.
In the event you must use different metals, consider using a plastic or fibre connector, or a dielectric ‘nipple’ or union between the joints. These insulating parts are typically made from non-conducting materials, and they act as a barrier and prevent the different metals from coming into contact. Dielectric unions are inexpensive and they have a washer and sleeve that separate the metals.
Sometimes applying a layer grease can be sufficient for insulating steel and aluminium parts. Encasing metal parts in plastic or epoxy or painting over one of the two parts to be joined could also be effective. Where possible, use the same metals or metals that are closely matched and are known to create less ‘galvanic current’.
If you are at all unsure about the possible ramifications of your DIY plumbing job, then call a professional plumber and have them check over your work before costly damage is caused.