In am plumbing my tanks and have to go from a steel tank that has a galvanized reducing bushing to copper. Should I put a brass nipple in between the galvanized and the copper or use a dielectric fitting or is there a better way to accomplish this. The fittings on the tanks are 2 1/2 and I have a galvanized reducing bushing down to 1 1/4.
PLUMBING STEEL TANKS TO COPPER
- Thread starter jimde
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
- Status
I think you need to ditch that galvanized fitting and replace it with a black iron fitting. Throwing that zinc coating into the boiler system mix seems to be considered a serious NoNo by the pros that post here regularly.
Grainger has black iron fittings in 2-1/2". They list hex bushings down to 3/4" in that size. Less than $8.
I've heard it both ways about the preference of putting a brass adapter between the steel and copper. I'd do it just because once you've got that 2-1/2 down to your copper size it won't be much money to put a brass fitting in there. You'll need some kind of adapter anyway if you're going to sweat fittings. Can't hurt.
Grainger has black iron fittings in 2-1/2". They list hex bushings down to 3/4" in that size. Less than $8.
I've heard it both ways about the preference of putting a brass adapter between the steel and copper. I'd do it just because once you've got that 2-1/2 down to your copper size it won't be much money to put a brass fitting in there. You'll need some kind of adapter anyway if you're going to sweat fittings. Can't hurt.
I did not now that galvanized was harmful to the boiler. I have a friend who is a commercial plumber that deals with hot water storage tanks for schools,laundramats,etc and told me that galvanized to brass nipple to copper is the way to avoid dielectric fittings. I have all the fittings ordered ,but they can be returned for different options.
You really don't want zinc or aluminum, for that matter, in your system. This was on a recent discussion, dissimilar metals , galvanic corrosion.
Rob
Rob
Galvanized fittings are iron (steel or various types of cast iron) dipped in molten zinc, also known as hot dipped, as opposed to electroplate, which gives a thinner, smoother coating, always silver in color, like all metals except gold or copper and it's alloys.
jimde said:
Use brass or the dielectric union, you can use a brass nipple to a copper reducing coupling, or a brass bushing, or combination.
The dielectric union would allow you to have a union fitting from easy maintenance, cleaning etc...
If you use a nipple, teflon tape and pipe dope. most plumbing fittings are now make over seas and are not round and they will leak
my $ .02
Tom
If you think ahead you can usually use a valve and they are brass so they make a good go between from steel to copper. Any time you can lessen fittings helps on costs
leaddog
leaddog
I will return to Grainger tomorrow and have them switch my order from galvanized fittings to black iron. The tanks already are equiped with gavanized fittings. One of the tanks was from a laundramat and the galvanized fittings are very corroded to the point that I am having trouble removing them. Even the exposed threads that are not in the tank have turned to rusted powder. Can anyone explain why this happened?
Here is a link that explains the importance of saying with certain materials.
http://www.engineersedge.com/galvanic_capatability.htm
Zinc the silver coating on the bushing in question. Zinc is used as a "sacrificial anode" placed into a system to be consumed on purpose to protect other metals in the same system. The way to avoid this protection is to use similar materials while building.
I sounds like you need to consider removing all the fittings and start from scratch. If you don't have a cutting torch here's another trick that you can do with a saw. The first cuts you make a back-wards piece of pie and then hammer it in. This works well for CI radiators too.
Does this help?
Rob
http://www.engineersedge.com/galvanic_capatability.htm
Zinc the silver coating on the bushing in question. Zinc is used as a "sacrificial anode" placed into a system to be consumed on purpose to protect other metals in the same system. The way to avoid this protection is to use similar materials while building.
I sounds like you need to consider removing all the fittings and start from scratch. If you don't have a cutting torch here's another trick that you can do with a saw. The first cuts you make a back-wards piece of pie and then hammer it in. This works well for CI radiators too.
Does this help?
Rob
Attachments
Thanks Rob, As I stated one of the tanks has completely rusted galvanized fittings. There is four 2 1/2" threaded ports along with multiple smaller ports. Two of them have galvanized plugs in them which I cannot get out even after heating them and using a four foot pipe wrench. The hex lug on the plug keeps breaking apart when I wrench on it. This particular tank came from New Orleans. I dont know if it was the water or the humidity that caused this problem on the galvanized. The tank is glass lined so interior corrosion is not a issue. The second tank is the same year which is ten years old and the galvanized fittings and plugs are in perfect condtion. This tank is out of Michigan. One thing that I noticed is that on the rusted tank I could not see any pipe or fitting tape or paste. The good tank has obvious pipe dope which will make it easy to get the fittings out. I will eventually get all the bushings and plugs out ( hopefully) and then clean all threads ,reprime and paint, then replace with black iron bushings to go from 2 1/2 to 1 1/4". From that point I will install the four inch brass nipple and then convert to copper. Its amazing how much time and energy it takes to do it right ( and money). Does the black iron to copper nipple to copper sound like the way to do this?
jimde said:
If you have a metal, oxygen, and electrolytic water, you get corrosion. If you find iron rust, then iron was the metal that was corroded. If you find rust on the exposed threads outside of the tank it is necessarily true water, oxygen, and an electrolyte were also present on the outside of the tank.
The corrosion of the iron was not caused by the galvanized fittings. Galvanized surfaces on pipes and fittings are put in place to protect the iron from corrosion by forming a protective layer of zinc compounds that prevent corrosion from attacking the underlying iron.
You typically don't find galvanized materials in boiler systems for two reasons.
First, once the oxygen inside the system is eliminated or absorbed, there is no longer any oxygen inside the system to support corrosion. You have iron, and electrolytic water, but no oxygen, so no corrosion (except by acid, hence the need to keep pH on the basic side). In this case the iron won't corrode, so there is no need to go to the expense of galvanized materials to prevent corrosion.
And on the outside of the system the system components are generally hot, warm, or at least above dew point, so no electrolytic water, and no corrosion except 'surface rust'. Here again, in the case of a boiler system, no need go to the expense of using galvanized materials.
Your laundramat tank, on the other hand, was presumably not part of a closed system like a boiler system, rather it was exposed to a continuously replenished supply of oxygenated water, so they used galvanized fittings to provide a corrosion resistant surface layer of zinc hydroxide/zinc carbonate.
The cut threads, however, weren't so lucky, so they rusted.
It is perfectly harmless to believe that galvanized fittings are not compatible with boiler systems -- even though it's not true -- since black iron should perform just as well and should be less expensive. Furthermore, galvanized is incompatible with propylene glycols based antifreeze compounds, a factor that may or may not need to be taken into account.
However, I wouldn't go out and buy new Chinese or Thai black iron if I had any serviceable galvanized pipe and/or fittings in inventory that would otherwise sit around waiting to be used.
--ewd
Thanks EW, very nice explanation. I looked at the grainger website and found two types of iron fittings. Black Iron or Black Malleable Iron. Should I stick with standard Black Iron?
jimde said:
As I understand it, "black iron" means simply "not galvanized". The 'iron' itself could be steel, cast iron, or malleable cast iron.
In the context of fittings like elbows, tees, reducing couplings, and reducing bushings, as you've noted it's narrowed down to cast iron and malleable cast iron. Malleable cast iron is cast iron that has been annealed to become more buttery and less glassy. In order to be suitable for annealing the cast iron recipe has to be controlled for proper proportions of iron, carbon, manganese, and so forth, so you can't necessarily anneal any old cast iron to make malleable, same as you can't smoke any old corned beef to get pastrami.
If you've ever dismantled an old boiler system you may be aware that cast iron is brittle and cast iron fittings can be smashed by backing them up with a sledge and pounding on the other side with a BFH. Not so with malleable, since it's called malleable for a reason, and it performs better under tension.
At any rate I would think that plain black iron fittings would be suitable since we're not piping in high stress or vibration applications.
(But if you're adding fittings to a steel tank somewhere in the project, you're going to want weldable steel couplings or half-couplings, not cast or malleable.)
--ewd
Well explained Eliot, I was thinking that, as the zinc coating was consumed, you would start developing multiple leaks.
I didn't get the fact that these were glass lined tanks. If the fittings are in that tight you might want to go with cleaning the threads and putting system together. It would be nice to start with a "clean slate" but how much heat and pounding can the lining take ?
Rob
I didn't get the fact that these were glass lined tanks. If the fittings are in that tight you might want to go with cleaning the threads and putting system together. It would be nice to start with a "clean slate" but how much heat and pounding can the lining take ?
Rob
RobC said:
The zinc isn't a consumable sacrificial anode, it's corroded itself into a highly insoluble surface coating. You should be fine if you clean up the threads and treat the surfaces with Permatex pipe glom. (Be careful of Permatex, it appears to be benignly inert and viscous, but it has a mind of its own and can crawl rapidly up your arm and has been known to leap small distances, like up behind your ear, for instance.) Plug the tank as a sub-assembly and pressure check with air and soap bubbles. Once the system is in service and any oxygen has been consumed there shouldn't be any significant corrosion from then on out, unlike the situation it suffered in the laundramat where new oxygen was supplied as makeup water moved through the system.
It would be a real shame to mess up the glass lining, but the integrity of the lining shouldn't matter so much for a sealed oxygen-free system. It's not my tank, but if it was I wouldn't be worried about flaking off some of the lining if I needed to get the fittings out with field expedient methods.
jimde said:
I believe you want "Class 150 Black Malleable Iron Fittings", not "Class 300 Malleable Black Iron Fittings, and not "Forged Steel Black Pipe Fittings".
Class 150 is 300 psi WOG / 150 psi saturated steam. Plain old Black [Malleable] Iron.
Class 300 is 300 psi WOG / 300 psi saturated steam. Same stuff, thicker than Class 150. If you actually need this stuff you're doing a job that you probably can't do legitimately yourself.
Forged steel is 3000 psi. Could be used instead of plain black iron but is more expensive and not needed, unless you need to weld to it. Can be welded-to by competent amateurs for use in low-pressure applications.
I ordered plain black iron, BUT NOT MALLEABLE. Class is 150. Says it's even useful for potable water. Looks like I screwed up again. I should have waited for a response to the last question before ordering. Should I change my order again to black malleable or leave as is?
I don't believe Grainger's sells any cast iron fittings that aren't malleable, but non-malleable should be fine for what you're doing anyways, so no problem.
--ewd
--ewd
OK, I got the plumbing under way. All fittings are out and all the threads are clean. There was alot of hard water deposit and rust in the tank. I was able to shop vac almost all debris out of the tank through the 2.5" openings. I think the rust I see is just deposit on top of the glass lining. The new steel plugs,bushings, and the copper nipples are in hand. The 11/4" ball valves came today. I have repluged the tank and have 2 gallons of rust,calcium and lime (RCL) remover that I will place in the tank and fill it with water. I was planning on letting it sit for a couple days and then doing the final rinse. Does anyone have any further comments or ideas for the final cleaning of my tanks?
These guys sell a lot of water treatment stuff to OWB owners but have a little FAQ page for closed systems. It's a bit of a product pitch but might be some help.
http://www.woodboilersolutions.com/facts_closed.cfm
http://www.woodboilersolutions.com/facts_closed.cfm
Well its been awhile ,but I have been busy at work and making wood. The cleaning of the tanks has went OK,but one tank has been difficult. I have used different rust removers ,but I have not been able to get the rust deposit or surface rust off of the glass lining of the tank. I hope that the lining has not degrageded and the rust is on the steel itself. I contacted the seller where I purchased the tank from and he said the rust is on the lining due to the heavy iron and hard water in his area. If I am not able to get it all off will this hurt my system?
Have you tried CLR cleaner ? We get iron build up on our Tree Nursery water filters and the stuff works well. Never been a big fan of As Seen On TV products. My iron was almost like mud stuck in a 200 mesh nylon filter. Nothing would clean it. 15 minutes in a dip of that stuff was like bleaching it. Took off all the iron gunk and the stain too. I don't know about dried on deposits but if something was worth a try this would be it. Can you get a pressure washer so after it soaks for a few days you can agitate the insides too ?
Rob
Rob
I like the pressure washer idea. I have used the CLR. It has made the water orange while soaking ,but it has not taken the surface rust stains off the tank lining.
- Status
Similar threads
