This article was posted before 01/01/2011 and is most likely outdated.

Fire Hydrant Corrosion (01-29-2K)

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Question No. 1:

I have a problem with fire hydrants corroding in an unusual manner. It seems that the outside of the bolt heads on the fire hydrants is disappearing; that is, they just shrink away. This isn't a citywide problem but it occurs intermittently here and there. The city Water Supervisor believes that it may be due to voltage potential on the fire hydrants. He suggested that bonding jumpers to the water pipes in the homes should be removed. I don't think that is the answer.

Do you know of a way that we can test the fire hydrant and its general proximity to see if there is a problem with voltage at the hydrants? Or, do you think that there may be another problem that is causing the bolts to disappear? This is a rather perplexing situation that I haven't been able to get any concrete answers to. I hope that you may have some suggestions for me or perhaps you can send me to someone that may have the answers. Thank you for any information you may have and, keep up the good work!

Joe Stammeyer,

Response No. 2:

My company has a similar problem that I would like help with. At one of our convenience stores, the copper water piping entering the building has rapidly corroded. The building grounding system is bonded to this copper pipe. Do you know what the cause and cure for the problems are? My guess was that current was being impressed onto the copper pipe causing it to corrode. I was going to suggest installing an anode bed in the ground to sacrifice itself over the copper pipe. What do you think?

Michael Chow,

Response No. 1:

I suggest you look into cathodic corrosion protection at the location this occurs. I doubt the house grounds cause the corrosion. If it were, it would occur everywhere there are houses or other buildings with that type of grounding (all buildings with power and metal water pipes).

Response No. 2:

I think the fire marshal just got a batch of cheap fire hydrant bolts and the heads are simply rusting away!

Earl C. Dean

Response No. 3:

Have the fire department check for dissimilar metals between the bolts and the hydrant bodies. This sounds like a classic case of electrolysis.

Response No. 4:

As a former Chevron engineer, I can tell you that pipeline corrosion is very complex. I suggest that you obtain a good corrosion protection manual or consult an engineer who specializes in corrosion problems.

Jesse Kray,

Response No. 5:

I don't believe grounding is any part of the problem. As an industrial electrician, it would seem the better you are grounded the less opportunity there is for any cathodic action. In Alaska here, we do use a ground grid under the oil tanks in our tank farms consisting of titanium and another sacrificial anode tied in with sodium bromide bags, at an outrageous cost. Have you contacted other fire departments around the country with a typical climate such as yours in seeking solutions?

I have no personal experience here but would give serious consideration to contacting the U.S. Navy about your metal corrosion problem. They must have a team of experts in metallurgical problems. The problem may be that if dogs are relieving themselves, the system is rich in hydrochloric acid thus creating problems.

Rocky Dippel,

Response No. 6:

like a cathodic protection problem. Major pipelines use this method to keep their pipelines from disappearing prematurely. I know that there must be some corrosion analysts in your area. I would contact them. Also, see if other water utilities in the immediate area are using cathodic protection. Your problem could be one of induction. Good luck! Corrosion problems are never easily solved.

Dale Kessler

Response No. 7:

It could be a weird case of electrolytic action, either due to the already stated potential differences causing highly rapid oxidation, or perhaps the bolts are of a dissimilar metal or alloy relative to the hydrant body. This alone would create metal destruction. The services of a competent metallurgical lab are required for this one.

Allan Soifer,

Response No. 8:

Disregarding bonding jumpers should not be done. One thing you might try would be to get a special alloy bolt that will not deteriorate by electrolysis, one that is the same strength as the steel bolt.

Charlie POPPE,

Response No. 9:

My name is Ed Chavern and I teach a seminar that covers this topic. With the correct meter, which costs about $100, the current and the source of the problem can be detected. Don't disconnect any jumpers. This is a problem that is not too difficult to correct.

Ed Chavern,

Response No. 10:

I believe the problem is something else; however, one way to test if there is voltage potential on the hydrants is to drive an independent ground rod (a short one) about 18 inches into the soil 3 to 5 feet away. Then take a voltmeter and read AC and DC voltages from the hydrant to the independent 'rod'. If more than a couple of volts are measured, then some electric circuit is not returning the current back to its source. This can be a bad connection or an open circuit. Investigation must take place by the Utility and/or nearby electric users. If higher voltages are detected, then underground corrosion is a strong possibility and can be very dangerous. The problem can be cathodic or anodic. Any metal part touching the earth will deteriorate where the current "gets off."

Ron Nelson,

Response No. 11

I would suggest looking for a source of DC, not AC current. The only source I could think of would be electrified trains. I worked for the Chicago Transit Authority for 10 years. This kind of thing was a common problem in and around rail terminals. If anyone still thinks home ground jumpers could be the problem (I doubt it myself), a piece of plastic pipe should be inserted by the city in new water main hookups OUTSIDE the home, at least 10 feet from the building. This will allow for the grounding properties to remain, while removing the possibility of current flow through the pipe.

It has been my experience that if there is a problem with AC current in a water main, it is the fault of the Power Company, who has loose neutral wires. Green scum (copper from the pipes) can sometimes be seen in washbasins and toilets. Dimming and brightening of lights is also a symptom.

Mark Elkins