I found there is a little leakage above a pump. How can I stop it?

 

Judging by the rust it looks like it's been leaking a while. How bad do you want to fix it? That will be a bit tricky for such a small leak as you can not tighten the fitting without cutting or unsweating the pipe. You can cut the pipe in the middle so you have plenty of room to install a coupling. Then you can try tightening it a bit more or you can completely unscrew the pipe, add new pipe dope or Teflon tape and put it all back together.

How old is the pump? Is it old enough to consider replacing the pump while you have it taken apart?

 

The system is about 11 years old. The issue is the thread connection failed. I probably will reconnect it in the Spring. It is not that bad.

 

Yes, dissimilar metals (copper pipe to cast iron pump) causes galvanic corrosion.

 

copper pipe to cast iron pump is not good. Is there a way to avoid corrosion? more Teflon/pipe joint compound?

 

Tapered NPT threads which you have seal by intimate metal to metal contact. Pipe dope or Teflon tape is a lubricant to make it easier to get the fitting tight without the metal galling. There are special isolation fittings with a plastic isolation piece in the middle to keep dissimilar metals from touching but quite often they are not used because they take up space and add cost.

 

This leak may be caused by galvanic corrosion - but I think that it is more likely that the joint simply wasn't sufficiently tightened originally. Notice the same type of connection joining iron and copper, located beneath the pump - it shows no visible sign of corrosion. With the many cast-iron and steel boilers in use, along with popular use of copper piping, it would be quite a chore to avoid dissimilar metal joints in boiler installations. Also, many local electric codes wind up requiring grounding of metal parts that might conceivably become inadvertently energized. I agree with Pilot Dane - electrically isolated pipe fittings are not frequently used.

 

Leaks around circulator flanges are common. Installing nuts bolt on top reduces issues from rust, easing removal. Annually put a few drops on oil on them just in case.

Gaskets made with black rubber have longer life than other colors. Remember white wall car tires.? Looked nice, but did not last.

Flat red rubber flange gaskets, while easier to install, deteriorate over years, become porous creating problems.

Recently had to replace steel flanges after red gaskets deteriorated leaving rust pits on surface. Used Taco round, 1/4" square cross section gaskets. https://www.supplyhouse.com/Taco-007...Pair-4662000-p

 

This leak does not appear to be coming from the flange itself or from the flange gasket. It appears to be coming from the joint from the male copper fitting where it threads into the flange female connection. In my opinion, likely caused by that threaded joint not being adequately tightened.

 

Subject of thread is how to handle leakage. The various solutions can raise a number of related ones.

When fixing or repairing something DH always looks for way to make things better.

Getting my rusted flange nuts off was difficult in hard to reach location. Next time will be easier.

Replaced rusted steel flanges with bronze. Live and learn.

Few are aware that different coloring agents used in natural rubber can reduce service life.

Hopefully some DIYer will benefit from DH words on related issues.

 

My temp solution:

0. cleanup the site
1. apply enough pipe joint compound
2. cut two strips from my daughter's swim cap
3. tight with a wire

After a week, it looks clean and dry.

 

Remind me to never let you repack my parachute.