upward facing dog

[AndyHpf]

It would seem to me that this basic problem, corroded pipe threads, must be fairly common, but either it isn’t or I don’t know the proper search terms. I do know a few potential solutions for general conditions but my difficulty is more specific.

A galvanized steel pipe come vertically out of the ground. On top of it is a cast iron fitting, a “no-freeze yard hydrant”. This has been in place for years, I know not how many. I need to remove the cast iron piece to replace internal parts but it covers the threads, they are below it. The cast iron fitting is larger than the diameter of the pipe. For reference, four turns of the pipe’s thread is exposed below the cast iron hydrant. They were painted over long ago.

I’ve used two large pipe wrenches, including trying to tighten it more as compared to unscrewing it, but can’t budge it in either direction. I tried banging on it for awhile with a hammer, hoping to shake something loose, but to no avail.

I understand that heating one part significantly, causing differential expansion in the pipe and cast iron, might help but have also been told heating cast iron unevenly will easily cause it to crack. That would create a major problem for me. Since I have no experience with that process, I am holding it in reserve as a last resort.

A correspondent has recommended wrapping the thread interface with a rag, saturating it with penetrating oil, and letting it soak for an extended time. I’m told many people of personal acquaintance to my correspondent have used this technique.

This makes sense when the threads are below the rag, and possibly could help somewhat with a horizontal joint, but I don’t see how the oil could be expected to be wicked upward, against gravity, through the threads.

After asking several times if any one of those people has successful experience with penetrating upward, I keep getting run around, unspecific answers. This leads me to believe the real answer is no.

What I’m asking here is if anyone knows this approach to work with corroded threads above the application point.

 

[GReynolds929]

That is a lot of words, holy moly.

If you can't get it apart and based on age you should dig it up and replace the whole thing. What brand and model? Do you have pictures?

 

[AndyHpf]

* Information is that the general installation depth here is 2 feet; I think that means the cubic foot of gravel at the bottom is below that 2 feet.
* It is in a location that will be extra difficult to dig. Digging it up means a hole large enough in diameter to keep the dirt out of the working parts at the bottom. There doesn't seem to be room for that as it is only about a foot from the foundation wall.
* If the threads at the top are impossible to work free, how likely are the pipe connections at the bottom to be cooperative?
* A new "hydrant" is somewhat difficult on my SS fueled budget.
* I view the throw-away approach, when a few $ of repair parts will do the job, as a special kind of corrosive insanity.
* It is a Merrill and looks much like this except not new and shiny

I supplied a link on Amazon for a Merrill frost free yard hydrant but this system say no go. It isn't hard to look up yourself.

 

[AndyHpf]

Also, according to the company's technical help, most often, the problem I have (system no t draining after being shut off) is solved by simply taking the cast iron part off the pipe, then turning the water supply on for a couple of minutes to flush out what ever is interfering with the drain valve. The second most common fix is to replace a small part at the end of the control rod, similar to replacing a faucet washer.

 

[Twowaxhack]

I have complete faith in Andy. You can do it !

Andy, have you met Ken ? He just joined the forum also !

 

[AndyHpf]

Interesting that there are comments but no one cares to address the question.

 

[Bird Doo Head]

Hello Andy,

PB Blaster and Kroil penetrating oils are two that I've found that wick upwards into threads by capillary action. (Like putting a stalk of celery in a glass of colored water.) Both products work well. Apply and tap the threaded area to set up a momentary vibration. The wicking will begin.

If you do decide to heat the parts, don't quench the cast iron. It'll surely crack. If the pipe still has water & is closed, heat from a torch won't help and could cause an explosion. Be careful!!

I believe the parts rusted together because there is no zinc left on the threaded parts & none on cast iron. Perhaps try re-installing the parts with anti seize paste instead of pipe joint compound. (I'd use Never-Seeze Regular Zinc. This is something I've used on cast iron-to-steel wet & wash-down location electrical parts for years.) If you don't get a good water seal, wrap over the anti seize with Teflon tape.

Best of Luck On Your Project!
Paul

 

[AndyHpf]

Hello Andy,

PB Blaster and Kroil penetrating oils are two that I've found that wick upwards into threads by capillary action. (Like putting a stalk of celery in a glass of colored water.) Both products work well. Apply and tap the threaded area to set up a momentary vibration. The wicking will begin.

If you do decide to heat the parts, don't quench the cast iron. It'll surely crack. If the pipe still has water & is closed, heat from a torch won't help and could cause an explosion. Be careful!!

I believe the parts rusted together because there is no zinc left on the threaded parts & none on cast iron. Perhaps try re-installing the parts with anti seize paste instead of pipe joint compound. (I'd use Never-Seeze Regular Zinc. This is something I've used on cast iron-to-steel wet & wash-down location electrical parts for years.) If you don't get a good water seal, wrap over the anti seize with Teflon tape.

Best of Luck On Your Project!
Paul

Thank you for an explicit answer. It is the first time anyone I asked responded with more than a theoretical concept, that is claiming to have actual, successful experience.

It seems very difficult to keep enough liquid on the bottom of the threads, against gravity and evaporation, to have any chance of wicking upward but I can now at least try it under some assurance it can actually work in this kind of circumstance.

It is no doubt possible to obtain some kind of anti seize paste, something I’ve never used before. I always though teflon tape would provide long term security against threads getting locked together. Apparently that isn’t true?

 

[pasadena_commut]

This is just a thought, so don't try it before somebody else chimes in. If you don't want to use a torch, maybe enough of a temperature difference can be achieved by going (mostly) in the other direction? Tape a cone of some sort of stiff waterproof material onto the pipe (picture the "cone of shame"). Put the cast iron part in contact with hot water (nothing extreme, say 150F, in a pot). Wait for it to warm up (assumes it is a small enough part to warm up this way). Then put the pot down and pour ice water (with ice chunks in it) into the cone on the pipe. Put the pot back in contact with the iron part. Wait 5 minutes or so. Put the pot down, tear off the cone, apply two big wrenches, one to hold the (still cold) pipe and the other to twist the iron piece on top, and try to wrench it off.

Personally, if there is no hurry, I would try several days of penetrating oil. Each day one time put the wrenches on and tap the top wrench with a hammer, so that maybe the impulse will break the rust loose. Using more force each day.

Alternatively, if you can replace the top part and there is enough pipe to work with, you could cut the pipe right under the iron, then use a die to rethread the pipe. Since the new threads won't be galvanized, use something to prevent corrosion when you put the new iron piece back on. Better yet, put on a brass piece instead, if that is an option. This approach could go very wrong if the pipe is so corroded inside that it won't tap properly.

 

[MicEd69]

Use a wire brush, and paint remover if needed to get the layers of paint off, to clean the joint between the pipe and the hydrant head. Apply the penetrating oil and it will wick up, defying gravity, into the mating threads of the two pieces. I seriously doubt heat will help unless you have an acetylene/oxygen set, so I wouldn't even try a propane or MAP gas torch on this.

When you said you used two large pipe wrenches, I assume you are using a pair of 36" pipe wrenches. If not, were using 24" pipe wrenches with a cheater on each? That is what you very well need to use on this hydrant. And be totally prepared to purchase a new one as disassembly of old items such as this may very well result in breakage of the pipe or the head.

 

[Twowaxhack]

I’d heat the female portion( the hydrant) for about 60 seconds with a torch ( mapp gas for you (air/acetylene for me) Just enough to expand the female threads to allow my wrench’s and my big man arms to unscrew it.

Then I’d use two pipe wrenches, probably 18” or 24” and try to unscrew it.


The threads may fail if they’re rusted/corroded and may twist off or stay in the hydrant. The pipe itself may crush.

In that case, I’d dig it up and replace the entire riser.

 

[Bird Doo Head]

Personally, I'd avoid quenching the cast iron if it's been heated. Ductile iron cracks very, very easily, malleable not quite as easily but can crack. I had a bar-be-que lid crack when it started snowing while I was cooking. Hot Lid + Cold Snow = Crack

Wrapping a cloth around the pipe where you want the penetrating oil to wick up might help keep the area damp with oil so it can wick better.

Andy asked about teflon tape and long term. I'm sure some protection is gained, but I've had troubles taking fittings apart. My guess is that the tape gets pushed off the crests of the threads, allowing metal-to-metal, then corrosion.

I forgot to mention that if you use anti-seize paste, leave the end two threads bare & flush the pipes well. Or, use NSF anti seize paste. Another option is to use a thick, castor oil & zinc based anti-oxidation paste. Penetrox is one brand. They are made for copper-to-aluminum electrical, but the castor oil/zinc ones work for steel to cast iron plumbing.

If the hydrant breaks off, I saw this no digging required hydrant: Yard Hydrant Made Easy™ - Never Dig Up an Outdoor Water Hydrant Again — Midwest Innovative Technologies, Inc. - Creators of the Patented Yard Hydrant Made Easy™ and Wall Hydrant Made Easy™
I don't know if it's a good thing or a bad thing.

Paul

 

[Jim Jensen]

just FYI, in my area, N. FLA, Kroil was HARD to find !!! I ended up buying from zoro.com, and they shipped it, $25 or so for a small spray can.....$$$, but it is VERY effective !!!! I used to tout PB Blaster, which IS good, but Kroil is better, for penetrating threads.....

 

[user 32496]

just FYI, in my area, N. FLA, Kroil was HARD to find !!! I ended up buying from zoro.com, and they shipped it, $25 or so for a small spray can.....$$$, but it is VERY effective !!!! I used to tout PB Blaster, which IS good, but Kroil is better, for penetrating threads.....

Yeah but keep it around if you ever want to remove the spark plugs out of a Ford Triton engine. The park plugs are notorious for breaking off in the head and then you have to use an extractor tool to get them out. Kroil is a miracle penetrant.

 

[Bird Doo Head]

Kroil is a miracle penetrant.

That Kroil smell sure likes to stay on your hands, doesn't it? Gotta resort to the stainless steel stink remover trick after I use Kroil.