Best method to clean water heater tank anode threads?

[pasadena_commut]

Took the anode rod out. Its threads are all fine, other than the remaining teflon tape. The threads in the heater were a bit of a mess. There was a blob of teflon tape about 3 threads up from the bottom which was a bear to get out. A toothbrush wouldn't budge it. It was finally scraped out along the threads, gently, with a big canvas sewing needle (the bent kind). The bottom 2 threads in the tank were nothing but rust. Ran the tap in and out, shaking it in a bowl of water in between to dislodge the grit, just until the bottom most tank thread was clean. Did this with about 37 gallons of water still in the tank, so that emptying it would carry out at least some of the rust particles.

The tank was a little odd after it was finally drained. The drain valve did not seem to be jammed - poking around with a long wire did not release anything. But pouring a couple of cups of water in through the anode hole didn't immediately pour out the drain. It took about 30 seconds to start dripping out, although it seems to have all come out in a minute or so and it stopped dripping then. Almost like it was filtering through sand.

Won't know for another 8 hours or so if the thread cleaning fixed the sealing issues from last time, since the tank is currently soaking with 3 gallons of vinegar in it.

 

[wpns]

That draining through sand' thing is a little disconcerting, when you get it back in service and before you power it up, I'd try draining it with the pressure on and see if you get any crud out of the bottom.

 

[MicEd69]

"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

Well Bird Doo Head, I think pasadena_commut has resolved his issue, but you are still a little confused on pipe and conduit threads.

Both rigid conduit and pipe have exactly the same tapered male threads. The dies they use to cut the thread on the pipe and conduit are identical. I am a Registered Professional Mechanical Engineer, and in my career I've been project manager on projects up to $680M in chemical plants and refineries. I've had electrical and piping subcontractors share pipe threading machines.

You are correct that female conduit fittings (couplings) and conduit taps do have straight threads. However, all female pipe fittings and pipe taps have tapered threads. Both male and female tapered pipe threads have a continuous taper of 1 per 16, or 3/4 per foot, or 1 degree 47 minutes, as does the electrical male pipe and male fittings. As such, if you use a pipe tap and run it all the way through the hole, you will ruin the female pipe connection.

See the following:





I did read the table wrong on the 3/4" pipe threads per inch in one of my earlier posts. I used 11 (rounded 11.5) instead of 14.

 

[pasadena_commut]

After 3 hours a little of the vinegar was drained out through the valve and its pH tested with some paper. It was somewhere between 6 and 7, so no point letting it sit any longer. (The starting vinegar is around pH 4.) Also a good indicator that there was a lot of calcium carbonate present, to neutralize that much acid that fast. Unfortunately the damn nylon drain valve was jamming every few seconds, and the flow rate was terrible. To get some motion the valve was disassembled, a wire pushed through a rubber disk of the right size, and the cap put on with the disk/wire instead of the normal valve. By moving the wire in and out through the rubber disk it was possible to get it to flow sometimes, and a ton of sediment came out, although with a slow flow rate. The tank was acting very strangely though, like at one point the cold water was opened for a few blasts and then we heard dripping. Somehow or other that cold water blew water up and out of the hot nipple, even though the tank wasn't more than a quarter full (and probably a lot less). The hot water line was not in place yet, neither was the anode, no pressure in the tank. The whole top of the tank was wet, as was the wall behind it, and the floor. It took quite a while to dry up that mess.

I don't think the tank is drained down to the level of the valve yet, not sure it can be with what appears to be a metric butt load of sediment still in it. It was getting late and dark, so enough for today. Tomorrow I will try to find some stiff plastic tube at the hardware store which can be threaded down through the open anode hole to vacuum out the remaining water with a shop vac. Once that is done the nylon drain valve will be replaced with a brass tube/ball valve. That is about 1/2" clear all the way through, which should be able to pass the sediment better.

 

[pasadena_commut]

The saga continues. Bought 10' of 1/2 PEX and an adapter to hook it up to my shop vac (more or less, lots of tape still needed.) Also purchased a Klein Tools ET16 boroscope, because at this point I really wanted to see what was actually going on in the tank.

Quick product review - the ET16 is inexpensive and the way the cable bends is excellent. Unfortunately the picture is just so so, and the way it takes pictures results in significant motion blur, which is a problem when 5' of camera cable is dangling in a tank. Also it only worked with 2 out of 3 Android phones we tried, and the dinky USB connector is sufficiently finicky that it takes 3 hands to use it. Luckily I had a helper. It was good enough for this, but only just barely.

Anyway, a peek into the tank showed a lot of water even though nothing was coming out of the drain. The PEX "catheter" was inserted into the tank three times, pulling up 4 gallons, 2 gallons, and a quart, along with quite a bit of sediment. (Note, this Ridgid shop vac was never very powerful, it didn't have enough oomph to vacuum sediment out of the tank vertically.) Another peek then showed what looked like a beach in the bottom of the tank.

With all the water hopefully gone the nylon drain was removed, revealing a wall of sediment through the hole. But it really was dry enough that not a drop came out. A 3/4" brass drain with a ball valve was inserted. A gallon of water was poured through the anode hole and captured in a bucket - containing a massive amount of sediment. A garden hose was attached and the tank drained. The cold water was turned on and off and back flow from a second hose was used to stir things up. A very large amount of sediment came out.

Sadly, like before, no matter how many times the stream ran clear (no new sediment) a backflow would stir up more. Once more the boroscope went in and it appeared that the large cake of sediment had been "sliced", with the region between the cold water dip tube and the drain, and a bit more on each side cleared out, but with the other 60% or so of the "beach" little changed from before. I think one reason the back flow didn't break up this mass is because the drain tube is aimed directly at the central flu, resulting in most of the flow being blocked from directly reaching the sediment.

So tomorrow I need to construct some sort of water jet want which will fit into the anode hole, to break up and dislodge this mass of sediment. My son has some tube bending and flare tools. I'm thinking maybe a piece of 3/8" copper with a slight bend to allow aiming, and female garden hose connector? Whatever the final construction, it has to be such that it cannot be lost down that hole!

 

[wpns]

Wow, sounds like what we call "An Easy Task".

If you install the new anode (or cut off the old anode and use it to cap the hole) fill the tank, bleed off the air, and open the drain into the hose with the cold water inlet turned on, will you get more sediment out? The hydraulics of the system full of water and under pressure have got to be different from letting a few gallons of water into the tank at ambient pressure...

Too late now, but I'd dump a gallon of cheap vinegar into the tank and let it sit overnight. If that works but not fast enough, I might upgrade to an appropriate dilution of muriatic acid, but that's hydrochloric acid, so don't mess with it if you don't know what you are doing, and ask the plumbing pros here for details.

 

[Bird Doo Head]

Your plan of copper tubing sounds good. Maybe flare one end and attach it to a fitting that ends in male garden hose threads. Make it longer than the distance to the bottom of the tank. You can hold it while "sweeping" the bottom of the tank with water from the hose and use the end of the tubing to scrape & sweep the cake- but don't bash the tank bottom. When I was a kid, we'd use a sorter version to clean car radiator tanks.

I'm kind of goofy about flushing my water heater every 4 months, the space was available so I put a permanent ball valve in place of the factory, plastic, drain. (Not my idea. got it from an on-line Family Handyman magazine article.) If the valve clogs while draining, I can poke inside with a plastic rod or even attach a vacuum hose.

I don't know if it meets code since the hot water would shoot straight out, instead of at the floor, if you bump the valve open. I took the handle off of mine and tied it on the valve body.

Thanks Micedge for more details about the threads.

I found my self puzzled, so I looked at my dies. The plumbing dies have one reduced end. The electrical dies don't. I measured the end of a black pipe nipple I had and a new piece of RMC. One was smaller at the end, one didn't. The thread forms, pitch, crest height, etc. all match.

Quote: "I've had electrical and piping subcontractors share pipe threading machines."
I've been on more than one job where lengths were rejected because the electrician used the plumber's heads in the machine. Once it was my apprentice. I remember that one very well.
We used to have a machine for each size we were running. Most recently a Ridgid 300. The fitters & plumbers were welcome to use it, but generally had their own. When shared, we'd have both die holders on the arms and flip down the one we needed- plumbing (reduced end) or electrical (not reduced end).

Quote: "As such, if you use a pipe tap and run it all the way through the hole, you will ruin the female pipe connection."
I ran my 3/4", 1" and 1-1/4' all the way through conduit couplings that I have in the fittings rack. Smooth as silk. I guess I don't understand.
By coincidence, yesterday I had to change the dip tube on my heater, as water was stacking. (It fell off the fitting). Since this was on my mind, I tried a tap. It was able to go all the way in to the tap holder- well past the threaded part of the tap.

Just To Confuse Things More...
Paraphrased NFPA 70 344.28 (if I remember correctly) "Where conduit is threaded in the field, a standard cutting die with 1 in 16 taper shall be used."
We were taught, and inspectors love to bring this up, that this was the thread standard- not the ends being reduced. it's from somewhere in ASME B.1.20, if I remember right. Auto plant in-house inspectors really go nuts on this.

And we can't use running threads for couplings (into other fittings = ok). NFPA 70 344.42 (B) I think. More confusion. People think this means the end reduces in diameter. It means no extra-long threaded portion. This way, both pipes in the coupling have an equal distance into the fitting.
We do thread longer than plumbing so that lock nuts and bond bushings will fit on both sides of a non-threaded item, such as a cabinet.

I stand puzzled and will peacefully remain so. (Since I'm mostly retired & don't have to care.)

 

[Bird Doo Head]

Boy Oh Boy do I ever waste peoples' time with my zillion words and I apologize.

When I taught, to clear up the confusing terminology, here's how I'd explain:
A) Install a factory made plumbing nipple or length of pipe in a panel or cabinet as though it were conduit. Make it up tight with locknuts, as usual.

B) Put the required bushing- plastic, ceramic or bond- on the end. It'll fall right off because of the reduced diameter for the last few threads.

C) Repeat Step A with an electrical nipple or a length of RMC or IMC. The bushing threads on properly & stays on.

 

[MicEd69]

pasadena_commut, maybe think about inserting a 10-penny nail in the end of your 3/8" copper tubing and squeeze the tubing with a pair of pliers or vise grips to make a nozzle of sorts. That will increase the velocity as you try to wash out the beach in you water heater.

And hey Bird Doo Head, if you didn't notice, I get a little wordy as well. And I don't look at it as wasting people's time since the engineer in me has the urge to provide information to people. They can either read it or not.

I don't understand your description of conduit dies not having a "reduced end". As both pipe and conduit threads have the NPT standard taper of 1 in 16, are you saying the downstream side of a "conduit die" is larger than the downstream side of a "pipe die"? In any case, the end of the conduit has to be smaller in diameter than the rest of the threads or else it will not have the required 1 in 16 taper. And I'm really surprised about lengths of conduit being rejected because of male conduit threads. I've never heard of such an issue in my 48 years as engineer and project manager in chemical plant and refinery project.

Quote: "I ran my 3/4", 1" and 1-1/4' all the way through conduit couplings that I have in the fittings rack. Smooth as silk." Yes, that would be the case. What I said was "...if you use a pipe tap and run it all the way through the hole, you will ruin the female pipe connection." In my earlier post, I said, "You are correct that female conduit fittings (couplings) and conduit taps do have straight threads. However, all female pipe fittings and pipe taps have tapered threads."

Male and female pipe threads are designed to contain internal fluids under pressure through intimate contact along a significant length of tapered threads. I'm sure conduit threads simply came about using the standard tapered pipe threads that existed, then used matching straight threads for the female parts for easier assembly as their purpose was just to keep external water from entering the conduit.

I've been retired from industrial work, and now just piddle with running house gas lines, plumbing, HVAC, and electrical work for myself, friends, and acquaintances. But this has been a very interesting conversation.

 

[pasadena_commut]

Too late now, but I'd dump a gallon of cheap vinegar into the tank and let it sit overnight. If that works but not fast enough, I might upgrade to an appropriate dilution of muriatic acid, but that's hydrochloric acid, so don't mess with it if you don't know what you are doing, and ask the plumbing pros here for details.

Already tried that. 3 gallons of vinegar was almost completely neutralized by all of the calcium in the tank in about 2 hours (pH rose from 4 to 6). For this much sediment it might take 20 gallons or more to dissolve the sediment. I'm hesitant to try a stronger acid given the age of the unit. Don't want to convert any incipient pinhole leaks into real ones. Note that the old anode rod, which was about 50% consumed, had only a fine layer of carbonate on it. Also the dip tube just looked like any other pvc tube in the boroscope - it was not covered with big blobs of crud.

Since we're all craving a hot shower after several days without, the sediment sweep has been postponed a day. Instead the anode was put back in and the pipe from the hot water nipple to the wall was replaced. Even though the threads from the anode had been cleaned with the tap, and with pipe dope, it still wept water when pressurized until it was torqued down to within a millimeter or two of the top of the fitting. Then it stopped. Putting on the hot water pipe was also a problem because the threads on both sides were pretty rusty from the previous one leaking slightly. Cleaned them for quite a while with a brass bristle brush and then the nuts would finally fit onto the threads. The previous pipe's nuts were if anything a bit loose, but maybe the corrosion chewed them up somehow, or the tolerances were on the large side. As I write this the unit is sitting for an hour to see if anything starts to leak, and if not, it will be fired up.

Tomorrow the over pressure valve comes out it will be washed from there. Easy to get to on this unit, as it is near the front, whereas the anode rod is tucked in pretty close to the cold water nipple and the flue.

 

[pasadena_commut]

The heater warmed up nicely from cold with just a few pop sounds

I did notice one thing though while once again checking the top for leaks after all four of us took showers - the cold supply line, installed by the plumber, goes very close to the flue, the closest approach is about 1 inch around 7 inches up from the nipple. Is that a problem? The supply line's label says that it is good to 180F, and my IR thermometer showed the flue at only 130F. On the plus side if the burner is on while cold water is entering the tank this will recover some of the waste heat. On the minus side, it is going to repeatedly thermally cycle a thin metal pipe (there is no plastic inside in that region, only for an inch or so at the ends), and for some materials that might eventually cause a failure.

 

[wpns]

repeatedly thermally cycle a thin metal pipe

You mean the cold water inlet, which I presume is copper pipe filled with water? Not a problem any universe.

 

[MicEd69]

I really applaud your tenacity and dedication to get this water heater up and running. It sounds like something I would do.

But when you mentioned being concerned about the age of the unit and possible pinholes being present, perhaps you should have considered a new water heater from the start instead of purchasing a pipe tap, socket for the pipe tap, new anode, vinegar, etc., and expend all this time to perform this work without having any hot water. I just hope all this will allow this unit to make it another few years at least.

Good luck!

 

[pasadena_commut]

According to the sticker it was made in 1995, so it is way past the typical lifespan. If the unit wasn't being maintained we would probably be on a third heater at this point. The maintenance costs aren't too high compared to the replacement costs. Since I'm retired now my time isn't really a cost.

I bought an inexpensive water detecting alarm to put under it, in case it ever does start leaking spontaneously.

Really crappy drain pan under it, by the way. It is almost exactly the same diameter as the unit and comes almost up to the bottom. So there is only a couple of millimeter gap in most places to see into the pan. "Luckily" it is slightly bent outwards in one section, perhaps because it was accidentally damaged when the tank was being installed. At one point during this process a little water was splashed on the side and it ran down into the pan. The drain hole is in the side and starts maybe 1/4" up, so the water just sat there. It was blotted out with an old sock. The boroscope just barely fit through the one expanded region, and showed that there was only water in that one place. That is good, because if the pan sloped down away from the front there would have been no way to dry it.