leaking copper pipe

Dan M

My hotwater system is setup for constant circulation . It seems that one down-side to this is that it would increase the errosion effect ? My second floor pipes are new 1" copper and are in the wall so a leak would be a real pain. The system heated well before the pump was set up to run constantly, should I consider going back to running it only when the boiler is heating ? . On a quiet day you can hear the flow pretty good.

thanks
Danm

joe_17

leaking copper pipe

I work in small office building which has a domestic hot water heat exchanger which uses steam for heating.This building is about years old.The copper pipe for domestic hot water lines are starting to get small pin hole leaks in them.The HX has a small B&G circ. pump to circulate water in the tank.There is another inline circulator pump for the building loop.I left out this building is 16 years old.Any ideas on whats causing pin hole leaks in the copper hot water lines.I am thinking maybe its electrolytic corrosion or errosion from velocity being to high.There has been a lot of repiping at the inline pump,maybe different types of metal used,will have to take a closer look.Could it be electrolisis.Is that the correct term.Thanks for any help.

Boiler Guy

pin hole leaks

I think you are on the right track with erosion - especially if the problem is close to fittings and directional changes. Good chance thhe piping was never reamed which will create additional turbulence too

Tom Anderson

Check to see if water is acidic. A ph less than 7.0 will also create the pinhole leaks.

George_10

We solve this problem

by using small injector feed pumps, which pump in the chemicals, which add just enough chemical (based on the system flow) to the system to keep it from becoming acidic. You are constantly adding new water to the system, therefore bringing in an abundance of oxygen which is released when the water is heated. This is a perfect situation for creating pin hole corrosion in the copper pipe. The addition of chemicals needs to be safe for water that is to be used for human consumption. We do this currently for large hospitals in our part of the country. But it would work in other situations. If you need further info please contact me direct.

jackchips_2

Many pin hole

leaks on domestic water lines are caused by high pressure and velocity. They wear from the inside out.

Domestic water pipe should be sized to keep the velocity below 8 feet per second for cold and under 4 fps for hot.

Doug_7

Leaking Copper Pipe

In recirculated domestic hot water systems, the cause of pin-hole leaks is almost certainly flow-accelerated corrosion or erosion-corrosion.

Cause is too high flow velocity. Happens when pump is too big or piping is a bit too small. Also the higher the temperature the faster the corrosion. Happens in "open" domestic hot water recirculation systems due to oxygen content in fresh water make-up. Does not occur in closed systems where oxygen is excluded.

High flow-velocity wears away the copper oxide protective layer causing pinhole. Occurs in turbulent areas such as where there are burrs on the end of piping due to cutting tube without reaming or downstream of elbows.

Prevention - Flow velocities should not exceed 5 ft per second up to 60 degrees C and should not exceed 3 feet / secong above 60 degrees C.

If you have an e-mail I can send you several articles on the subject.

ScottMP

PH

You said this was Steam, I would look at the Ph level in the condesate as a source of the problem. Also what these other guys have said about velocity and erosion is right in the money.

Scott

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joe_6

leaks

Thanks everyboby for reply.I am thinking it is velocity as has been suggested.

Doug_7

Domestic water leaks

Pin-hole leaks in domestic hot water recirculation systems is a real problem and expensive to fix, especially when piping leaks inside walls.

I assume your DHW recirculation system is in a 2 storey home and is just there to keep domestic hot water quickly available to second floor taps ?

Suggest you check pipe flow velocity and make sure it isn't above 3 feet per second. Look at pump curve - if you know the pressure differential across the pump you know the flow. You might be able to reduce the velocity by reducing the size of the circulator.

Grundfos make a neat little domestic hot water recirculation pump. It has a built-in thermostat and a timer. It only recirculates DHW when it needs to - the thermostat turns pump ON only when the DHW temperature drops and shuts it OFF as soon as it is warm again. The timer does not allow the pump to run during parts of the day when you would not want hot water - eg. not at night.

Saves money on power to run the pump, DHW heating cost and on piping repair.

You would be surprized how much heat is wasted by constant recirculation DHW through uninsulated piping. My DHW recirculation heat loss in a small condominium was 40% before I insulated the DHW supply and return piping and after insulating it is only 19% of total DHW heating demand.