Holding Tank Fitting Replacement Presenting a Challenge

[IOLANI]

So I discovered that I had a crack in the 1" Street Elbow fitting on top of my blackwater holding tank that would spew some blackwater each time the V bunk head got flushed. Obviously this led to some unpleasantries. Merely touching the elbow to analyze the situation made it crumble (looks to be original cast bronze) and shear off flush. After several days of applying penetrating oil I attempted to back out the broken section of nipple using the appropriate size (#9) extractor using a 3/4 drive breaker bar and quite a bit of force to no avail. Won't budge.
I'm faced with either stepping up my game to some serious cheater bar placed over the breaker bar and hope for the best or try a different approach all together. Applying the Hippocratic oath of "first do no harm " I'd rather not end up somehow tearing out entire top plate or distorting the surrounding area. I'd rather leave a situation where if need be I could always chase the thread with a 1" pipe tap if necessary.

I'm thinking maybe a hacksaw blade or three corner file to make some vertical slots in the broken fitting to possible relieve the tension and then try and back it out again or just try to fold it in and chip it out in pieces with a small chisel. I'd likely lose the broken bits into the tank but hopefully they'd be small enough to cause no harm or get sucked out on the next pump out.

Anybody tackle this exact issue before...? Any other suggestions or advice.

 

[Briankinley2004]

Maybe take a heat gun and heat it up good to soften the old pipe dope and see if that helps?

 

[IOLANI]

Maybe take a heat gun and heat it up good to soften the old pipe dope and see if that helps?

So I think I've read in other posts that there is a solid plate glassed into the top of the tank that holds all the treaded bungs....is it made of steel...stainless steel ? Aluminum ? Brass or bronze ?

 

[Captain Ralph]

On our last Hatt tank issue like this, There was also a Dumbetic multi tank level sender, Offering a 3" service hole.
I chipped out the threads, then dock side pump out, and cleaned the black tank with a shop vac.

It did stink, lost of stuff removed that was not going to the pump out or pick up.
Many trips to overboard (after dark) from the 16 gallon shop/vac on the above deck.
Took lots of rum (days) to clear my pallet. But the clean up was well worth it.

Trust me, you really do not want to pull that service plate off of the glass tank top.
A real cleaning of that tank helps your future, if you survive the cleaning..☺☺☺

 

[Bob Quinn]

I would say put 3 cuts in it with a sawzall or jigsaw to relieve the pressure like you are saying.

The bad part is you would be likely cutting into the threads.... so how do you get the new piece to seal right? Maybe screw new fitting in with 4200 or screw in then 4200 around it?

Just thoughts. It's not like it's seeing 100 psi, just needs to seal and hold a vacuum when pumping out.

OR, as I have done with things like broken taps on the cnc machine... this might be tricky:
Find a drill that is the correct "tap drill" size for the thread and drill out the remaining pipe.
All that would be left is the pieces of metal in the thread that you would hopefully be able to pick out with a pick. The problem with that might be finding the drill motor big enough to do the job and holding it without it ripping your arms off. They make large magnetic drills that will mag down to a steel plate, but you probably have no steel plate or even room enough for one of those units.

(the CNC shop version of this method is to use a carbide end mill and circular interpolate the hole to the tap drill size if you can picture that)

OR use a die grinder and remove the material down to the threads, but that would be a pia too. However a die grinder with a burr style bit might be more controllable if you wanted to put 3 cuts in it. (more controllable than say a jig saw) Also if you just go deep enough to reach the edge of the threads you might be able to do it without damaging the threads.

Another thought would be some kind of acid that might eat into the brass but not the stainless? I don't know if something like that exists? Or what about the strong acid used for cleaning clogs that dissolves almost anything? Maybe it would relieve the corrosion? <--o.k. probably a bad idea, just thinking out loud

 

[whoover]

I would try just one cut with a Sawzall then try to hammer and chisel the remaining piece out. It's tough because of limited room to work and the tank flexes a little each time you hit it. An air chisel would be a help if you can get a big enough air source. If you can get an oxy-acetelene torch on it that would help with your extractor, a heat gun is not hot enough.

Walt Hoover

 

[Sadey]

Not sure I would put an open flame around that tank. I personally have seen what happens with a lighter and a fart.

 

[bostonhatteras]

When a new tank access has to made into an existing tank, typically it's done with a pre-threaded plate positioned below the fiberglass tank top which then the new configured tank top plate will thread into. The way to get the pre-threaded plate into position through a hole that naturally would be smaller than the underneath plate, if round or square, would be to cut the underneath plate into two equal halves and then both halves are easy to install. If you make the underneath plate oval or rectangle then no need to cut in half provided one segment of underneath plate is smaller than the long segment of the tank cut out. The underneath plate will have four or so threaded holes that will allow the plate to be attached with screws to the tank through the fiberglass. With the bottom plate adhered with screws and 5200 it will become a permanent part of the tank allowing the new top plate to be removed whenever you want. You can do this on a new section of the fiberglass tank or remove the original tank plate and make a new bigger plate where the original was. The hatteras plate is relatively small for this mod, but could be done. The hatteras plate is likely 3/16 plate, I think. the original plate can be drilled and retapped to a larger size thread but its not easy in place. Bronze/brass has an absolute hate relationship for twist drills, CNC is a far better option. Any competent machine shop can make you the matching bottom and top plates with the necessary threaded holes, although you might have to supply the brass plates to them. Is Bob Quinn listening?

 

[bostonhatteras]

drill motor

WOW someone else who uses the correct term!!!!!!! A drill does the cutting, a drill motor turns the drill. I've found my people haha

 

[jmooney]

As the holding tank is vented, a fitting installed does not have to be air tight. I would use a die grinder to thin out the remaining part of the broken 90 or nipple . Then make 3 slots as deep as you can stand. The pieces should be able to be driven out with a chisel. Making a new plate has got to be a real hassle.

 

[Captain Ralph]

I would try just one cut with a Sawzall then try to hammer and chisel the remaining piece out. It's tough because of limited room to work and the tank flexes a little each time you hit it. An air chisel would be a help if you can get a big enough air source. If you can get an oxy-acetelene torch on it that would help with your extractor, a heat gun is not hot enough.

Walt Hoover

Would you want a torch over a tank of methane fumes?

 

[IOLANI]

Thanks for all the replies guys lot of good input. Ralph you scared me with that story, I don't think there's enough rum (or beer in my case) in the world to get me to shop vac my blackwater holding tank.

It's good to know I could fashion entire new bung plates if it ever came to it, I'm going to do my best to salvage the existing one in the meantime. I think I'll try to slit the fitting and chip it out and hopefully wont do too much damage to the threads. As noted as long as I can get it to be liquid tight that will suffice. I was thinking back to my machinist days in Exxon and remembered the large NPT tapered reams we would use prior to tapping any large NPT threads as they would help shape the hole in the proper size. Perhaps one of those would help clear the old fitting . The problem with all of these tools is they have a large drive on them, like 1" square. I don't like operating them with a ratchet and socket or breaker bar because your pulling one-sided....a large T-handle setup would have a much better feel to it.
And yeah I've envisioned the big old 1-5/32 bit grabbing on me with a 110v drill motor and the prospect of an open flame with methane gas also crossed my mind when thinking about heating it up so we're all thinking alike.

I shall report back

 

[IOLANI]

Success! Using a hacksaw blade I cut a single slit it the 12:00 position and then a long narrow chisel to fold the fitting inward. As soon as I made the cut you could actually see the tension relieved in the broken fitting and it came out easily and I kept all the pieces. . Amazing actually as I could not budge this thing with a 2 ft long 3/4 drive breaker bar. The problem with those extractors in a case like this when it's thin wall pipe is they exert a lot of outward force so at the same time your trying to turn it you're also making it tighter. The new fitting threads in nicely.

It did leave a thin scar in the original thread but I'm pretty confident I can get that to seal, maybe use some No1 or No2 Permatex. Tempting to use 5200 but if for some reason it doesn't seal I may never get it out again.

While I'm in here it's a good opportunity to change out the hoses which are relatively short since they only run next door to the through hull /holding tank selector.

Thanks again for the help it's always nice to be able to bounce some ideas back and forth before trying something. Misery loves company.

 

[Captain Ralph]

It is great you were able to recover the old pieces. You will miss the opportunity to clean your black tank.

 

[IOLANI]

It is great you were able to recover the old pieces. You will miss the opportunity to clean your black tank.

Haha....I'm ok with that Ralph.

On a similar note while I was in here I managed to wrestle off the cap to the clean out and look inside. I can see it's the original brass tube and, knock on wood, it's still working well. I suppose it would not be a bad idea to replace it before in breaks off but for now I think I'll list this under "leave well enough alone" or "if it ain't broke don't fix it"....

 

[Sadey]

It’s so nice to get a win every once in awhile!

 

[SEVEN]

If it’s necessary to seal it don’t use 5200. The strongest would be 4200. Great job.

 

[whoover]

Nice job, these kinds of boat repairs can go downhill fast sometimes. As far as using heat go's, fill the tank with water, problem solved. What do you guys eat for God's sake!

 

[Bob Quinn]

Glad you got it. I know how frustrating that had to be..... these damn old boats haha!
on the up side you probably never felt so good about fixing a sh*ter.

 

[rwaldrop13]

I had to replace the elbow on Pau Hana - Just FYI I'd go to Ferguson Plumbing Supply, they're most likely to have the same fitting, and they're a nationwide company. Probably pricier than some other vendors, but I spent a rainy afternoon running around Ft Myers before remembering them from previous experience. They were great.