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27narrow 12-21-2007 10:52 AM

Pinhole Leaks in Copper Piping
I have a radiant heat/gas boiler and keep getting pin hole leaks in copper piping close to boiler. It most likely is the high velocity of the water but we have replaced the pump with slowest one around. Our Plumber wants us to throw out the boiler (it's only 5 years old and house is the same age) but i cannot believe that there is not a way to fix this design problem. I am getting very tired of constant replacing of the copper tubing every 6 months or so. Is there anothe metal that is stronger than cooper i suspect i cannot use stainless steel as this is the drinking water. We have tested the PH level in the water and all is well there (we have a water softener)
It seems such a waste throwing out a fairly new boiler
I have come a accross several individuals having the same problem but no one is offering any solutions


jogr 12-21-2007 01:20 PM

Well 304 or 316 stainless steel is perfectly safe for drinking water but I have no idea if it will help. Is the high velocity water really your drinking water? Normally your potable water system would be heated indirectly through some type of heat exchanger. So the potable water lines would not be subjected to the high velocity that might be occuring near the pumps in the radiant loop.

I would think any reputable dealer and installer could recomend an appropriate solution. It might not even be a piping or water quality issue, maybe something like air in your system which causes excessive wear from cavitation or oxidation. I would try talking to the boiler manufacturer and a different dealer/installer.

Bondo 12-21-2007 02:08 PM


as this is the drinking water.
Ayuh,........... I'm having a Hard time comprehending That.........

You can't be pumping your Drinking Water thru the floor before the Tap,..??..........

redline 12-21-2007 05:40 PM

Is this well water?

What type of copper is installed? (l,k,m)

Have you tried PEX?

skymaster 12-21-2007 06:10 PM

Pin holes in copper is a SURE sign of highly acidic water. get it fully checked out and most probably you will need a neutralizer inline with your softner

XSleeper 12-21-2007 08:20 PM

Are there dielectric unions between all copper parts and all galvanized ones?

cjett 12-22-2007 09:45 AM

Have you tested the hardness of your water to make sure the water softener is doing it's job? You can buy inexpensive hard water test kits just to rule that out.

27narrow 12-27-2007 12:24 PM

Thanks all for the reply
Yes, the water hardness has been tested and that is not the problem. This pump i believe gets the hot water to my faucets if i am correct.
THere is no doubt it is the speed of the water that is the problem that has been deceded by couple of plumbers. I think the cooper is 3/4 and my plumber says stainless steel will not work in this case ... we have replaced the parts we can with plastic tubing (radiant heat tubing) but i am pretty sure there is a problem mixing metals ....

cjett 12-27-2007 12:53 PM

I agree that you don't need much water flow for this application and the pump is causing the pinhole leaks. I have dealt with this for many years in a commercial building and the only thing that has solved the problem, is a properly operating water softener. If the softener quits for whatever reason they have pinhole leaks all over the building until the unit is put back in operation. Then about a month later everything settles back down, with no more leaks.

Also did you check to see that you have the dielectric union where dissimilar metals are present, like was asked above? If none of that helps, maybe you can switch to PEX if that is allowed, not sure about that as I've not used it for anything yet.

Marlin 12-27-2007 06:27 PM

How does fast moving water cause pinhole leaks? That's a new one to me.
How do dissimilar metals cause pinhole leaks? That's new to me too. It can cause corrosion and ultimately leaks at the joints but shouldn't be causing leaks in the lines.
Are we talking about a recirculating line here? Hot water coming off a coil? Or heat lines?

XSleeper 12-27-2007 10:52 PM

I think you answered your own question, Marlin. Dissimilar metals can cause corrosion (one metal acts as an anode, one acts as a diode) meaning copper atoms detach and go elsewhere. That's why dielectric unions are needed between copper and galvanized. Not sure why you think corrosion would only happen at joints, though. The corrosion attacks the copper parts, not the solder. I've found this happens most often at elbows where the metal is already thin.

I've never thought that "fast moving water" could cause it, so that's a new one on me too, but it sounds plausible if the corrosion breaks free and acts as an abrasive.

I almost always see this happening next to a water softener. (lots of elbows, no unions)

Marlin 12-28-2007 05:25 AM

I guess I see how the disimilar metals could cause it, I've just never seen it happen. It just seems that the amount of corrosion/acidity absorbed by the water at the joint wouldn't be enough to do any damage to the copper.

XSleeper 12-28-2007 09:08 AM

The water is the conduit for the electrolysis that takes place between dissimilar parts. Its similar to electroplating. It is due to positive and negative charges, not acidity. (and I meant to say anode and cathode above... not anode and diode)

cjett 12-28-2007 10:11 AM

In my search for possible causes of the pinhole leak problem over the years I was told by more than a few plumbers and supply houses that a recirculating pump will cause electrolysis also.

27narrow 12-28-2007 12:18 PM

pinhole leaks
THank you all for the replies
You are right it is the recirculating pump that pushes the water faster than 4 feet per second. This speed causes the cooper not being able to create it's natural barrier (on the inside) . We have had the pinhole leaks during the last year in copper elbows, copper straight lines etc. THis is though in a very small area just around the boiler were the cooper is attached to the boiler not close to the water softener.

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