My home is 10.5 years old. I have a 75 gal gas HW heater for a 4700SF two story house. It uses a small hot water circulating system that keeps hot water to all fixtures at all times. It works great.
Nine months ago, I experienced a pin hole leak in the recirc return line about 8 feet before the pump. Four months later I experienced another pin hole leak about 3 feet before the pump. In both cases I have saved the leaking section and cannot see any visible corrosion or erosion at the pin hole leak point.
How do I determine the root cause of these leaks and correct.
Replies
I have read that there has been some pretty crummy copper pipe (technically, tubing) from overseas that's probe to pinhole leaks.
Do you have unusual minerals in your water?
I was told of a problem with "bad copper pipe" during the mid 80'S. I have no confirmation of that. My home was built by a custom - not mass builder in 1991. I bought it as it was being completed.
My water supply is Fort Worth city water and no signs of unusual corrosion or build up in any lines includiing where the pin holes are.
Where did the leaks originate? I had a pin hole develop because I inadvertantly shot a trim nail into it.....it took about 4 months to soak the floor.
Ditch
Both leaks were in the water heaters closet - no activity that would cause damage from the outside. Appears to be thinning wall in minute spots from the inside.
No signs of hardness deposition inside or outside.
Does anyone know about galvanic action in a copper pipe causing this?
A lifetime ago in a former life, I saw this problem in a very high power radar at Whte Sands Missile Range, NM. It even used triple distilled water for a coolant. The designer built in a high purity copper nail w/ a VERY sharp point to sacrifice itself, but no maintenance instructions to ever check it. Matter of fact, it wasn't even on the drawings! Any time you have electricity even near a copper water line, you can get galvanic action. Doesn't take many milliamps over several years to wear it out. Also, your system is running 24/7 to circulate water - lotsa time to work on the tubing. Betcha if you very carefully sectioned the tubing at the hole and miked the wall thickness you would find it was thinner for a considerable distance around the hole.
DonThe GlassMasterworks - If it scratches, I etch it!
http://www.wsscwater.com/cfdocs/copperpipe/pinholescroll.cfm
Here is some local information from Maryland about a pinhole leak outbreak.
Edited 9/3/2002 8:38:35 PM ET by Patrickjd9
Interesting web site. Obviously I have much more to learn about pitting in hot water copper pipe.
If the leaks were near fittings, here's a scenerio reported by a few: Plumber pad a whole wad of flux on the pipe end or in the fitting (someone described a plumber dipping the pipe in the flux insread of painting a bit on). Years later hole develop where there was an exposure to a lot of acid (the flux).
Could there be more erosion of copper in the position of the leaks? I thinking about a 24/7 circulator pump and there will be places, near 90s, that see a higher velocity, maybe even turbulant flow. That, coupled with a water that is a bit corrosive (acidic or very pure), could cause thin-wall pipe to leak. What horsepower (1/25? 1/40?) is the pump? Model number or performance curve?
Note, as you get these leaks fixed, that there is K, L, and M pipe. M is the thinnest and what everyone uses (except underground) because it is the cheapest. In your situation, until you figure it out, I'd step up to type L copper tubing. It's only $2 more per 10 foot length.
David Thomas Overlooking Cook Inlet in Kenai, Alaska
I'd like to reply to two issues.
1. We have an outbreak of pin hole leaks in the Summerville, SC area. The pipes effected are about 25 to 30 years old. To date, Puplic Works has not found any answers. I believe the problem is that type "M" copper was used almost exclusively. Type "L" should have been used in the walls and type "K" under ground. What type copper is yours? It should be marked on the side.
2. I think you need to get an electrician to rewire your circulater pump. On 24/7 is not only a waste of electricity and wear and tear on your plumbing, it's a waste of hot water. I use a relay that is activated by the bath room light switch. This enables the pump. The pump is then turned on and off by a thermocouple attached to the pipe. I always have hot water at my finger tips, and my pump only runs a few miutes a day.