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Ricky
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Discussion Starter #1
Here's my question and a little history.
Q. What are the opinions as to how copper pipe develops pinholes in domestic H/W re circulation lines?
We've installed several with not so good results. They were mostly installed in houses on municipal water systems with neutral PH levels so acid didn't play a roll. They usually have a 1/40th hp or smaller pump and at least 3/4" pipe size through-out. The earlier installs ran continuously and the later ones have thermostats and timers. I've yet to get pin holes in the later installs but I'm still a little worried just due to the havoc we encountered with the continuous systems. I've also started using cpvc on the entire loops and have had no problems with those yet but if I leave just a short nipple of copper anywhere it causes problems.
I've been told it's an Ox problem due to too much velocity. I've been told it's a copper quality problem but I doubt it due to so many different jobs with the same problem and all were type L copper. We've even seen pinholes if fittings.
What do you think?
 

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Professional Bullshioter
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6,092 Posts
My opinion would be one of 2 things.

Too much velocity. I use a 92 watt B&G circ pump.

or

When you cut out a section that has pin-hole leaks, does it have an excessive amount of residual flux in the area of the hole?
 

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Ricky
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Discussion Starter #3
I tend to think velocity is the killer too. The sections we've cut out don't really look to be corroded as in too much flux, they look more eroded like too much flow. Maybe I need to use the much smaller pump along with the Tstat and a timer. ILPlumber have you had any of these pinhole problems?
 

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٩(͡๏̯͡๏)۶&#
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I agree with the velocity theory. It's only happening on the recirc lines and not the rest of the system right? If that's the case, the constant erosion of the pipe due to velocity must be playing a major role. If you have been using cpvc without any problems then why not just use plastic from now on?
 

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Ricky
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Discussion Starter #5
I agree with the velocity theory. It's only happening on the recirc lines and not the rest of the system right? If that's the case, the constant erosion of the pipe due to velocity must be playing a major role. If you have been using cpvc without any problems then why not just use plastic from now on?
That's what we've decided to do on new or accessible work, I'm searching for more info for the inaccessible retro fits that are piped with copper. I just want to know what people are running into. We are constantly asked to cut the wait times for H/W to master baths and kitchens and I don't like the single pipe systems due to the luke warm water in the cold side. I'd like to hear from plumbers that have used recirc lines with copper pipe to see if they are seeing pin holes, and if not how are they piped. I just hate not knowing the actual cause of the pinholes or the correct way to do the install. It's just a pet peeve of mine.
 

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I've run acroos many places where the design engineers oversize the recirc pumps. I guess they just want to make sure circulation is eveywhere. What I've done in the past is install automatic control valves on each recirc line in a high rise condo and their pinhole problems almost totally went away. They were made by Griswold Controls and were called "K Valve". They can be ordered for whatever GPM you want. I believe what I installled were 3/4 GPM. You only need a little flow to keep the hot water available and these keep the velocity down no matter how oversized the pump is.
 

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Professional Bullshioter
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ILPlumber have you had any of these pinhole problems?

Never. We have never in 30 some odd years in business had to repair a pinhole leak. It must be a combination of the feet per second flow with the chemical makeup of the water.

With the loop insulated the flow is VERY low. I use these to set flow. Made by Tour and Andersson. They also come in solder end. Couldn't find a pic of that in my 20 second search.
 

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I'm ALWAYS fixing pin hole leaks ,,,, hot and cold lines . Doesn't work with the pump theories .

I think is manufacturer AND flux .

My .02
 

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Ricky
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Discussion Starter #10
Cal
Are you talking well systems? Low PH can eat copper in short order but it won't be found in public water systems. Do a PH test next time and you might be able to sell a acid nutralizer.
 

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Cal
Are you talking well systems? Low PH can eat copper in short order but it won't be found in public water systems. Do a PH test next time and you might be able to sell a acid nutralizer.

NO SIR !! Public water systems . Fairfax County Va . BIG city system .

Happens ALL the time :cry:
 

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٩(͡๏̯͡๏)۶&#
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In my area it seems to be related to chlorine and flux. The PH is always in the low 8s and the chlorine is 3.4 to 3.8 ppm. The leaks are almost always at or near the locations of flux and usually on the bottom of the pipe where the flux collects when liquid. The older hard copper systems with minimal flux used (better workmanship) last longer than the newer soft copper systems. I don't ever do repairs on soft copper systems that are flared or compression (no flux used). It seems that the chlorine somehow accelerates the corrosive abilities of the flux.
 

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I also notice that 9 out of 10 leaks are on the cold side of the system. This is due to the fact that the anode in the heater tank reacts with the chlorine in the water and causes it to precipitate out of solution. This theory is supported by evidence of an increase of pin holes on the hot sides of systems with newly installed tankless heaters (no anode). Water velocity and the total volumes that the pipe has seen also play a role though to a lesser extent than the chlorine and flux.

I hope this helps. Please keep in mind that water chemistry is complex and what I have observed in my area may not apply to your area. Water in Fl and Il is different, and so is the water in your area.
 

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Former Moderator
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Question - By velocity, are you referring to the rate at which the water flows through the copper? or the general velocity of hot water vs. cold? Hot water from a water heater is not identical to the water from the main. Could the answer be that it is directly related to the heat properties and not the constant motion of the water being recirculated? If my question is stupid, just disregard and don't slam me.

"Water is a compound made of the elements hydrogen and oxygen. The smallest
particle of water is a molecule made of two hydrogen atoms and one oxygen atom.
Unless the temperature is absolute zero (0 K), all molecules are in constant motion.
When the sample is a solid, the molecules are touching, but vibrate continuously. If
the sample is a liquid, the molecules are still touching and move in random
directions, tumbling over one another, colliding with each other and the walls of the
container. This activity will demonstrate the result of molecular collisions and how​
a change in temperature affects this molecular motion. . .

At higher temperatures, molecules contain more kinetic energy. (Kinetic energy is
energy due to motion.) The reason they contain more kinetic energy is they are
moving at greater speed. This greater velocity results in more collisions per second.
Furthermore, these collisions are more energetic. This means that, in the warm
water, the faster molecules will be distributed throughout the container more​
rapidly"
 

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٩(͡๏̯͡๏)۶&#
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8,329 Posts
Yes.

No.

Question - By velocity, are you referring to the rate at which the water flows through the copper? or the general velocity of hot water vs. cold? Hot water from a water heater is not identical to the water from the main. Could the answer be that it is directly related to the heat properties and not the constant motion of the water being recirculated? If my question is stupid, just disregard and don't slam me.

"Water is a compound made of the elements hydrogen and oxygen. The smallest
particle of water is a molecule made of two hydrogen atoms and one oxygen atom.
Unless the temperature is absolute zero (0 K), all molecules are in constant motion.
When the sample is a solid, the molecules are touching, but vibrate continuously. If
the sample is a liquid, the molecules are still touching and move in random
directions, tumbling over one another, colliding with each other and the walls of the
container. This activity will demonstrate the result of molecular collisions and how
a change in temperature affects this molecular motion. . .

At higher temperatures, molecules contain more kinetic energy. (Kinetic energy is
energy due to motion.) The reason they contain more kinetic energy is they are
moving at greater speed. This greater velocity results in more collisions per second.
Furthermore, these collisions are more energetic. This means that, in the warm
water, the faster molecules will be distributed throughout the container more

rapidly"
 

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Another source of pinholes that I come across is "copper chloride". When we have larger size homes with 4 or 5 bathrooms and two people living there, all of the piping doesn't always get used. That standing water causes the chlorine from the municipality to destroy the protective layer formed inside the tubing (cupros oxide) and then the chlorine eats the tubing from the inside out.

We usually tell our clients to operate all fixtures at least every two weeks.

Not that this addresses the op's problem, but it's interesting what actually destroys copper tubing. :)

I believe that errosion of copper tubing begins to happen at 8feet per second, but I could be wrong.
 

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I It's only happening on the recirc lines and not the rest of the system right? If that's the case, the constant erosion of the pipe due to velocity must be playing a major role.
Would not the velocity of the water be the same throuhgout the system on the hot side? If so then the entire hot side should have pinholes and not just the recirc line.


quote=trick1;38395]Another source of pinholes that I come across is "copper chloride". When we have larger size homes with 4 or 5 bathrooms and two people living there, all of the piping doesn't always get used. That standing water causes the chlorine from the municipality to destroy the protective layer formed inside the tubing (cupros oxide) and then the chlorine eats the tubing from the inside out.[/quote]

I will agree to this. We mostly see it on 1/8" copper ice maker lines.

Another possiblilty is stray voltages of electricity (millivolts/amps). This voltage may come from an appliance that is tied to the water line, within the electrical field of a wire, etc...

If the problem is under a slab the lines could be buried in "Donna Fill" with out any protection.
 

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٩(͡๏̯͡๏)۶&#
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How does standing water cause a reaction to take place?

As far as the voltages, I say hog wash. Where would these voltages becoming from? An AC power source? AC does not cause corrosion only DC. Dc currents do not produce moving magnetic flux lines and therefore cannot induce a voltage into neighboring pipes.
 

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Certified Lunatic
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How does standing water cause a reaction to take place?

As far as the voltages, I say hog wash. Where would these voltages becoming from? An AC power source? AC does not cause corrosion only DC. Dc currents do not produce moving magnetic flux lines and therefore cannot induce a voltage into neighboring pipes.
Ever hear of galvanic corrosion? The stuff we use dielectric nipples and unions to prevent? The water touching 2 widely different metals can induce it's own voltage.

The pipes are often bonded and a bad main panel ground, perhaps a high resistance connection on the neutral lots of juce could be flowing through the pipes...:eek:

Ever do the science experiment where you make a battery out of various fruits and vegetables, a penny, and a nickel? The longer that water is stagnant the more stuff leaches into is and the more corrosive it becomes...
 
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