Looking for expertise in electrochemical corrosion of water pipes 1

I am evaluating the source of elevated lead and copper in water from a water supply system that includes municipal distribution, local distribution, and building piping. Building piping is the likely source of the metals and electrolysis is a anticipated to be a potential mechanism. Is there a way to pinpoint where electrolysis is occurring in the pipe? The water first out of the tap had lower concentrations of copper in it than what was collected after purging 1.3L out of the pipe. To me this suggests that electrolysis occurs further down the pipe. Thanks.

 

[gibfrog]

1) What is the quality of your source (Cu,Pb,Ph,Ca,etc..) prior to entering the building or your control volume (Like the ambient quality in the main.)?

2) Newer buildings all should have back flow preventors, so the copper and lead should not be from a newer building, unless it is your building. Copper piping and lead solder over 5 years old should be protected by calcium deposits. How old is your building. Have you cut open any existing piping to see its condition?

3) Copper pits in aggressive water (low Ph) and copper suffers from velocity pitting. How high are your copper pipe velocities?

You need to supply better info for better answers.

Clifford H Laubstein
FL Registered PE 58662

 

[BobPE]

I am not sure what you are asking either. You say electrolysis and this to me means the presence of current which means something different when it comes to water system pipe corrosion. There is a school of thought out there that electrical currents carried by copper pipes contribute to corossion of the pipe. This may be true for concentrated areas where DC voltage is applied, but as for AC current, I have yet to see this occur and from my research, it is not a contributing factor to L and C corrosion. Do you really mean corrosion? If you do, corrosion most likely is the mechanism and is caused by aggressive water in the water purveyor's distribution system or water that is made aggressive by a building plumbing system. The corrosion you are talking about on second draw samples is coming from down in the pipe and is caused by high residence times of water in you plumbing system. Corrosion, once it is occuring, happens throughout your entire system and is worst in areas of the system where water sits for long periods of time. I have worked on building that were over 10 years old and had L and C problems. Usually they pipes season after 5 years like Cliff said, but this is not always the case or the water purveyor changes the water system and subsequently strips the protection from your pipes.

Cliff also mentioned errosion of your pipe whice is related to velocity and should be checked.

Where did you collect a sample from? This would be a good starting point.

Bob

 

[cmsu]

i agree with gibfrog and bob p.e., also high levels of dissolved oxygen can cause aggressiveness in water, generally associated with surface waters. are you mixing surface water with ground water? if so, the problem could have been there for a while and the surface water has brought the problem out. are you sampling hot or cold water? heat accelerates corrosion. also, once again i agree with the age of the pipes, and the composition of the pipes and here the pipes were manufactured. some pipes made overseas (galvanized) were substandard at the point where the pipe was "rolled" together. also, check with the water supplier, they should be complying with the lead and copper rule, and/or adding a corrosion inhibitor to the water. check to see if a water softener is being used, the hardness in some source water varies dramatically and if the softener is not adjusted properly it can cause the conductivity to increase. let me know what you find.