Best method to clean water heater tank anode threads?

Help Support Plumbing Forums:

pasadena_commut

Well-Known Member
Joined
Sep 10, 2016
Messages
166
Reaction score
32
Location
,
I replaced the anode on our American Water Heaters tank with a KA90 purchased directly from the manufacturer in 2011. In 2016 it was pulled out and inspected and 95% of it was still present. Both times it was a pain to remove and I had to use an impact to break it free. The second time it was really hard to make it stop leaking. I tried a bunch of things, like varying amounts of tape, and cleaning the tank threads with a brass toothbrush and some vinegar. Eventually it sealed after thread cleaning, teflon taping, and then tightening down hard. That was not with the impact, but by hand. ("Hard" being relative, I am pretty skinny so what feels like a lot of force to me might not seem like much to a bigger guy.) Both times I verified that there was electrical connectivity between the nut on the anode and the steel of the tank. Also, to the extent I could see the threads in the tank, they didn't look chewed up, but it wasn't shiny metal, so probably some rust.

Time to replace this rod again. I want to do a better job of cleaning up the tank threads this time, because I suspect the sealing problems were due to some chunks of rust that were still present on those threads. I have seen videos which suggest using a 3/4" NPT tap, and others which suggest that working a 3/4" nipple in and out is sufficient. Is one of these better than the other, or is there something in between that is better than those extremes? I'm afraid that the tap might cut new threads, and the nipple is continuous thread, so it doesn't really have a way to work rust out, other than maybe by driving it down the spiral and into the tank.

(Yes, I did ask in another thread about ways of getting vinegar into the tank without taking out the anode. I neglected to check my notes first, so I didn't see that this maintenance was now due.)
 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
A 3/4" pipe tap is obviously tapered and will only cut "new threads" if you run the tap farther than you should. And as you inferred, it will do a MUCH better job cleaning the female threads. If you use it, you will not need any other cleaning methods, and it will not hurt a thing if you go another turn after it gets fully engaged. Cutting another turn will not hurt a thing. I would use a tap and Teflon pipe dope instead of Teflon tape.
 

pasadena_commut

Well-Known Member
Joined
Sep 10, 2016
Messages
166
Reaction score
32
Location
,
Found a 3/4" NPT tap. Next problem - it has an 11/16" square shaft. There must be some sort of socket for a ratchet with an 11/16" square hole, but no luck so far finding one. Does some size 12 pt or 8 pt socket fit that square well enough to use?
 

Bird Doo Head

Active Member
Joined
Jan 11, 2010
Messages
42
Reaction score
7
Location
,
I am not a plumber, but to clean up and give low electrical resistance to old, female rigid steel conduit threads we use the steel fitting brushes that are meant for cleaning copper tubing fittings before soldering. (Picture attached)
Get one that is considerably smaller diameter than the opening on your water heater. Press it lightly against the threads and run your hand around in a clockwise circle a bunch of times.

If you prefer a tap, an adjustable wrench can be used to drive the tap since the threads are already present and you don't need a lot of down force. Be sure to stop before the last thread so the tap doesn't fall in.

Hope this helps you save you some money.
Paul
 

Attachments

RS

Well-Known Member
Joined
Dec 25, 2019
Messages
419
Reaction score
146
Location
USA
Found a 3/4" NPT tap. Next problem - it has an 11/16" square shaft. There must be some sort of socket for a ratchet with an 11/16" square hole, but no luck so far finding one. Does some size 12 pt or 8 pt socket fit that square well enough to use?
To fit properly you need a 8 point socket, a 12 point will work but not very well.
 

RS

Well-Known Member
Joined
Dec 25, 2019
Messages
419
Reaction score
146
Location
USA
They do make tap handles specifically for this, but you need a lot of room to turn them. Most people would just use an adjustable open end wrench, you're just cleaning, not cutting new threads.
 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
I am not a plumber, but to clean up and give low electrical resistance to old, female rigid steel conduit threads we use the steel fitting brushes that are meant for cleaning copper tubing fittings before soldering. (Picture attached)
Get one that is considerably smaller diameter than the opening on your water heater. Press it lightly against the threads and run your hand around in a clockwise circle a bunch of times.

If you prefer a tap, an adjustable wrench can be used to drive the tap since the threads are already present and you don't need a lot of down force. Be sure to stop before the last thread so the tap doesn't fall in.

Hope this helps you save you some money.
Paul
Remember, pipe threads are tapered, so unlike machine thread taps, you never run the tap all the way through. You must stop the tap WELL BEFORE the topmost thread on the tap even gets close to the top of the hole being chased or tapped.
 

pasadena_commut

Well-Known Member
Joined
Sep 10, 2016
Messages
166
Reaction score
32
Location
,
https://www.amazon.com/Lisle-70940-3-Piece-Tap-Socket/dp/B000Q6SG4A says that "#10 is for 11/16" (18mm)", so either that specific one, or https://www.amazon.com/TEKTON-Drive-12-Point-Socket-SHD23318/dp/B07R754QBP if you want to save a few bucks should work.
I tried Lisle - none of their tap sockets are right for this. That 11/16 does not refer to the size of the square hole in the socket but to something else.

I think the next step is to take the tool to O'Reilly's or Autozone and try all the 12 point sockets to see if one works.

If not...

There are 4 point sockets, and probably somewhere somebody has one for 11/16".

As RS pointed out their are 8 point sockets (although not in any local hardware stores), and this one might work:

 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
I tried Lisle - none of their tap sockets are right for this. That 11/16 does not refer to the size of the square hole in the socket but to something else.

I think the next step is to take the tool to O'Reilly's or Autozone and try all the 12 point sockets to see if one works.

If not...

There are 4 point sockets, and probably somewhere somebody has one for 11/16".

As RS pointed out their are 8 point sockets (although not in any local hardware stores), and this one might work:

pasadena_commut, you do not need a socket to chase threads. A simple crescent wrench or an open end wrench of the correct size will work just fine. You will be able to screw the tap in by hand quite a ways. Using the wrench, carefully screw the tap in 1/3 to 1/2 a turn, then unscrew it about 1/4 turn. Repeat this process until the tap gets rather tight. You are not trying to cut any threads, you are just trying to scrape the rust and residue from the existing threads. As there are tolerances in taps and cut threads, you will likely have some metal cuttings, so I would have someone hold a shop as close to the hole to try to catch as much of the debris you will be producing by chasing these threads. Some will probably fall into the water heater anyway, but maybe you can suck up the majority of it. I don't think you will need and lubricant, but you could use food grade mineral oil if you are afraid of getting the tap stuck and tearing the threads in the water heater. I mention this because it sounds like you have very little experience with metal working.

Good luck.
 

pasadena_commut

Well-Known Member
Joined
Sep 10, 2016
Messages
166
Reaction score
32
Location
,
A 13/16" 12 point regular depth socket (from O'Reilly's) fits the square base of the tap pretty well. There is a tiny amount of play but given the small amount of torque which will be applied here it doesn't look like rounding off the square base of the tap will be a problem.

Would cooking oil be OK instead of mineral oil, as I have the former and not the latter? I actually do have some tool cutting oil, but that stuff is nasty and I wouldn't want it in the tank. Either way, it looks like some oil is likely to drip into the tank. The tank will be flushed afterwards, but since oil will spread out on top of the water, and possibly stick to the tank walls, it is probably going to stay in there until it breaks down or very (VERY) slowly dissolves into the water. The youtube videos on RV water tanks show them being hosed out afterwards, which seems like it might do a more thorough job than on a home water heater since the RV ones are mounted sideways.

Hopefully draining/rinsing the tank will remove most of any metal bits which fall in.
 

wpns

Well-Known Member
Joined
Feb 15, 2022
Messages
143
Reaction score
34
Location
Tamarac, FL
Don't get so carried away, use water as a cutting fluid (I can't imagine a hot water tank without some rust particles in the bottom), just turn the tap enough to clean out the threads (just remove the rust, don't cut any new threads), and use teflon pipe dope or teflon tape to keep it from leaking and make it that much easier to remove it for your yearly inspection next year.
 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
A 13/16" 12 point regular depth socket (from O'Reilly's) fits the square base of the tap pretty well. There is a tiny amount of play but given the small amount of torque which will be applied here it doesn't look like rounding off the square base of the tap will be a problem.

Would cooking oil be OK instead of mineral oil, as I have the former and not the latter? I actually do have some tool cutting oil, but that stuff is nasty and I wouldn't want it in the tank. Either way, it looks like some oil is likely to drip into the tank. The tank will be flushed afterwards, but since oil will spread out on top of the water, and possibly stick to the tank walls, it is probably going to stay in there until it breaks down or very (VERY) slowly dissolves into the water. The youtube videos on RV water tanks show them being hosed out afterwards, which seems like it might do a more thorough job than on a home water heater since the RV ones are mounted sideways.

Hopefully draining/rinsing the tank will remove most of any metal bits which fall in.
No don't use vegetable oil. As wpns said, you aren't cutting new threads. However, my concern is that it appears you are not mechanically inclined, and to you very well may cut the metal in a few places due to thread tolerances, threads that are rusted, and/or threads that have galled. And if you are not experienced in cutting threads, you stand the risk of not going far enough to chase the threads adequately to get a nice seal, or you possibly will go too far and get the tap stuck unless you use some lubricant. And water is NOT a lubricant for chasing/cutting threads in metal. You can get 3 oz. of mineral oil at Walgreens for a little over $2.00.
 

Bird Doo Head

Active Member
Joined
Jan 11, 2010
Messages
42
Reaction score
7
Location
,
Quote from MicEd69: "No don't use vegetable oil."
I once did a months long wiring project at A. O. Smith. I got to know my liaison from Smith, so I'd get after work tours of the plants. The cast-in threads on the tanks' bosses were being chased with a Dry tap to clean up the threads & remove the glass particles left from over-spray.

I remember being surprised, so I asked my father, originally a German tool maker by trade. He said cast steels are always machined dry and ground wet because cast steel does not undergo a eutectic transformation when cooling due to the very low carbon content, plus the graphite can be high.

For tapping or drilling, the chips would make a slurry & pile up in the tool and the work. The same rule holds true for cast iron. ( I don't remember if the water heater tanks were cast steel or cast iron. I think steel. The plumbers here will know for sure. The heating boiler water sections were cast iron.)


If you're concerned about sending the tap in too far, twist-tie a piece of wire between the lands on the tap at the length you want & leave a tail. A scrap of solid copper wire works well. It'll stop the tap at the depth you want it to stop & also keep it from accidentally falling in. (I do this with high voltage bus ducts when there are live parts below.) If you've got any laying about, small zip ties work.

If you can return the tap, to save money, maybe a pipe nipple will clean the threads for you. Perhaps shrink the end threads with a grinder or file- but ask the plumbers here first. I've got one I made for a one-time size that is a sharpened nipple with a tee on it. The tee is held from unscrewing with a conduit lock nut. A bar or screwdriver through the tee is the "adjustable" handle.
 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
Quote from MicEd69: "No don't use vegetable oil."
I once did a months long wiring project at A. O. Smith. I got to know my liaison from Smith, so I'd get after work tours of the plants. The cast-in threads on the tanks' bosses were being chased with a Dry tap to clean up the threads & remove the glass particles left from over-spray.

I remember being surprised, so I asked my father, originally a German tool maker by trade. He said cast steels are always machined dry and ground wet because cast steel does not undergo a eutectic transformation when cooling due to the very low carbon content, plus the graphite can be high.

For tapping or drilling, the chips would make a slurry & pile up in the tool and the work. The same rule holds true for cast iron. ( I don't remember if the water heater tanks were cast steel or cast iron. I think steel. The plumbers here will know for sure. The heating boiler water sections were cast iron.)


If you're concerned about sending the tap in too far, twist-tie a piece of wire between the lands on the tap at the length you want & leave a tail. A scrap of solid copper wire works well. It'll stop the tap at the depth you want it to stop & also keep it from accidentally falling in. (I do this with high voltage bus ducts when there are live parts below.) If you've got any laying about, small zip ties work.

If you can return the tap, to save money, maybe a pipe nipple will clean the threads for you. Perhaps shrink the end threads with a grinder or file- but ask the plumbers here first. I've got one I made for a one-time size that is a sharpened nipple with a tee on it. The tee is held from unscrewing with a conduit lock nut. A bar or screwdriver through the tee is the "adjustable" handle.
Bird Doo Head, the issue here is cleaning up the rust, any galled steel, and any tolerance differences between the tap and the existing threads that may exist. And you apparently still do not understand that a pipe thread is tapered. There is absolutely no need to mark a depth on a pipe tap because if you tried to run it all the way through into the tank, you would break the tap off well before the tap would drop into the tank. And depending on the taper existing in the anode boss, you cannot establish how far you need to go to properly chase the threads in that boss. It's more of a feel and an experience thing.

Also, my suggestion on a lubricant is because it is obvious that pasadena_commut is not a plumber, mechanic, machinist or engineer. I have had to remove broken taps from holes because the operator just started running the tap in without backing it off periodically and without using any lubricant. One needs to develop a "feel" for taping and chasing threads. You can't learn to swim watching an internet video either.
 

pasadena_commut

Well-Known Member
Joined
Sep 10, 2016
Messages
166
Reaction score
32
Location
,
MicEd69's characterization of my expertise is spot on. So I bought a 3/4 NPT 14 female to female coupler to practice on with the tap. It was a cast iron part and the threads had some obvious imperfections. The tap was run in until it stalled, then out, then in, etc. until it felt pretty smooth. Without having cut any metal (or only a tiny amount) the tap would go in more than 6, nearly 7 turns. Then I tried to screw the replacement anode into the same coupler. The anode threads looked very clean, other than a couple of very tiny shiny spots on the thread crest. I counted 8 thread crests on the side of the anode. Tried to run this anode into the coupler and found it would only go 2.5 turns from first engaging to sticking hard enough it wouldn't turn by hand any further.

This raises a question I had not considered before - how many full rotations once the threads are engaged should a normal anode go into a normal water heater before meeting resistance? And how many turns with a wrench after that would be typical for a full seal?
 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
1653181039520.png

With a 9/16" engagement length and with 11 TPI (treads per inch) your final assembly would theoretically be a little over 6 turns. You should be able to turn the anode another 2.5 to 3 turns with a wrench I would guess, so I would think you are OK. Again, I would use Teflon pipe dope rather than Teflon tape.

Good luck.
 

pasadena_commut

Well-Known Member
Joined
Sep 10, 2016
Messages
166
Reaction score
32
Location
,
The total thread length below the nut on the new anode is 1/2". (Plus or minus a smidge because of course the threads are at an angle.) The diagram appears to skip the first two turns of thread on the male side, which would seem to preclude getting enough threads into the "A" region for "Normal engagement". (1/2" * (8-2)/8) = .375". But 9/16" is .5625".
 

MicEd69

Well-Known Member
Joined
Dec 4, 2021
Messages
341
Reaction score
87
Location
Missouri
The engagement is for pressure piping, so I wouldn't worry about meeting the 6 turns. Impact wrenches are often used to remove these anodes. Put some Teflon paste on the anode and tighten is up. If it leaks, just tighten it some more. You'll be fine.
 

Bird Doo Head

Active Member
Joined
Jan 11, 2010
Messages
42
Reaction score
7
Location
,
"And you apparently still do not understand that a pipe thread is tapered."
Yes, I do understand that the end of a plumbing pipe is reduced in diameter.

In ASTM terminology, the word "tapered" for NPT refers to the thread form or thread shape, not the fact that the last two or three threads on a plumbing fitting are of a reduced diameter. NPT means "National Pipe Taper". It's a standardization of the thread shape * isn't related to the diameter reduction.Take a look at Tapered thread form versus Buttress thread form for an extreme example.

My father, a German engineer with 2 PhDs (one of which was in mechanical engineering), explained thread standardization to me and it stuck. He was around long before even SAE threads were standardized.


Maybe This Explains Better:
National Pipe Threaded pipes & nipples used in plumbing have the end 2 -3 threads reduced in diameter. They are called "tapered threads". The threads are tapered shaped. The pipe is tapered at the end.

National Pipe Threaded pipes & nipples used in electrical do not have the end 2 -3 threads reduced in diameter. They are called "tapered threads". The threads are tapered shape, The pipe is not tapered (reduced in diameter) at the end.


In a hardware store, pick up a nipple for rigid conduit. Hold it next to a nipple for plumbing & you'll see the difference. NFPA-70 (National Electrical Code) requires "tapered" threads. The form, not the diameter reduction. ASTM & NEMA prohibit reducing the diameter of the electrical pipe at the end of the thread. So they're tapered, but not tapered. A mechanical engineer can explain better.

Go to a project. You'll see that the fitters & plumbers have one thread cutting machine & the electricians have another. The dies are different. I once saw hundreds of lengths of rigid conduit get rejected on an auto plant re-tool because the electrician used the plumbers' threading dies. Why? The threaded portion reduced in diameter at the end.



"There is absolutely no need to mark a depth on a pipe tap because if you tried to run it all the way through into the tank, you would break the tap off well before the tap would drop into the tank."
Since I've accidentally sent taps into cabinets more than once, that statement surprised me. I just took a 1-1/2-11.5 NPT tap and sent it all the way through a threaded fitting. It went in the top and came out the bottom. Repeated with 3/4-14.

The micrometer shows that after the starting threads the diameter is the same for the entire threaded portion & the plain body of the tap is a smaller diameter. This holds true for all of my NPT, UNF, UNC, Acme & JIS taps over 6 mm diameter. Plug, forming or cutting taps- it doesn't matter. That's so one can cut threads longer than the tap with an extension rod. (A long tap would be brittle & snap.)

Thus the reason that I put a wire "flag" on the tap when I can't fit a tap wrench and have to use a different driving tool that does not have a grip on the tap.
The wire "flag" isn't marking anything. It is to keep the tap from falling in. (safety belt)

But, we are way off the original poster's question & I apologize for contribution to the wayward path.
Paul
 
Last edited:

Latest posts

Top