Copper or Black Iron?

EngineerinBoxford

Is the reason that black iron piping is most often used for the actual connection to a hydronic boiler because it was strong enough to support the near boiler equipment or is it because of the potential for corrosion between dissimilar metals and the desire to move that out away from the boiler?

Garth

Ron Jr._3

We use black iron

for the reason you state first ........ to support all the circs and flow checks and expansion tank .



We adapt to copper from iron 4 or 5 times with every typical install . And remove a boiler that has the same amount of iron to copper fittings . I've never seen corrosion happen due to dissimilar metals . I've seen plenty of corrosion due to a fitting not being tight enough !



The place where we see leaks the most ? Steel nipple into an iron circ flange .

icesailor

Flanges:

Teflon Pipe Tape and pipe paste is a wonderful thing. Correctly applied is almost assured of no leaks.

Mark Eatherton

Technically speaking...

The piping near the boiler is not supposed to support the weight of anything but the pipe itself. That said, it does come in handy during assembly, and once installed is supposed to be supported from above or from below, but not bear weight on the boiler. So technically speaking, it doesn't matter.



As for disimilar connections, using a brass fitting between the two disimilar metals avoids any galvanic issues. Even a brass ball valve will do the trick. Theoretically, the two metals have to be connected in an "electrolytic" (oxygenated water) solution in order to complete the battery required for galvanic action. In a true closed loop system, the oxygen is removed and or consumed in a "bridging" process, hence it doesn't matter.



ME

Ron Jr._3

Bridgiing process ?

Is that why the water has a grayish color and smells like bile when we drain a boiler ?     

Ron Jr._3

Correctly applied

has different meaning for many people .........



We use Teflon tape and thread sealant . The trick is to apply sealant to the outer AND inner threads of the fittings  . Haven't had a thread leak in forever !

Mark Eatherton

Muy muerto agua....

Interpretation; Really dead water ;-) Yes, that is why it stinks.



I had a job the other day that was a 5 year old W/Mc aluminum boiler, that didn't pass the water test strips they send out with a service kit. I had to drain some water out in order to make room for the chemicals I had to pump in to alleviate the bad water condition, and the water I drained smelled SO bad, it almost turned my stomach. Hydrogen sulfide gas is my best guess.



ME

icesailor

Correctly Applied:

"Correctly applied" doesn't include tape on the union nut and nothing on the union face. And by "nothing", I mean no sealant on the mating faces of the union. Same with flare fittings. I have removed quite a few flare fittings where the only pipe tape used was on the nut. Not on the male threads of the fittings but on the male threads that connect the nut.

Ron Jr._3

i agree somewhat

Applying sealant to the threads of a flare or a union does nothing.



But we routinely add a dab of soft setting sealant to the mating surface of flare fittings. And pesky unions. System 2000 recommends this practice when installing their hot water heat exchanger. Trying to put one of those in without some Dope on the union ends will guarantee you a leak.



Would you care to elaborate why doing this is a no no?

Ron Jr._3

Makes you wonder sometimes

How old some of this water is in some systems! We replace equipment that looks all original over 5 decades old.........

Jean-David Beyer

Someone should bottle that old scuzzy water

in 1/2 pint screw-cap bottles. Whenever someone wants to use a hot water heater to provide both hydronic heat and domestic hot water without even a heat exchanger to separate the domestic, have them sniff that and then reconsider.

gennady

tread sealant

Application of tread sealant on female part of the joint leads to pushing this sealant into the piping system and contaminating inside of the piping system. Properly done treaded joint does not need any sealant, because on conical treads when parts joined together pressure between  joining surfaces is so great that molecules of 2 joining metals starting diffuse into each other . It is same as welding. Pro dope, consisting of lube oil and polishing paste, does 2 things: makes easy to rotate joining parts and removes unevenness in the joining surfaces. Thread sealant does not make good joint, proper treading and application of  pro dope make good joint.

As per support of parts, first those parts must be supported and then connected, not the other way around. Principal of support is, if any part of system is removed, the rest of the

system must not move.

gennady

SUPPORT

I would say, boiler must not support any pipe, all piping must be supported in such a way, that if boiler is removed, piping stays unchanged

Ron Jr._3

It don't matter how careful

you are with thread sealant , it WILL get into the system .



I'd rather have too much sealant on a joint than not enough and have to back out 4 inch and a 1/4 black tees . Been applying all kinds of sealant to the inner threads of countless thousands of joints and hardly ever had an issue of sealant messing things up inside a system . A good hot purge will clean the system out of everything ...



As far as having proper support of all the parts .................. 



Again I'll go by experience here and say we never had an issue building a black steel header on any boiler and having problems removing parts from it . We add indirect heaters to existing boilers all the time and are able to back out at least one black steel fitting to connect a supply or return ,



Agree to disagree ?

gennady

deleted

deleted