Thank you to everyone for your suggestions and insights.
Well I would think it would be not too hard to repair with just soft solder? Cleanliness is super important with any sort of soldering. I'm not familiar with those water heater units, is it actually bronze and not copper or brass?
sold - that is my next attempt
I don't actually know what the material is, and I don't know how to find out. I assume it is some type of bronze based on the label:
I sanded down the weld and area around my previous attempt. I cut a patch from a short length of copper pipe and shaped it to fit the contour of the boiler. I sanded the inside of it, coated both surfaces with flux and wired the patch tight to the tank. I then soldered it on; preheating the surrounding tank area until the flux began to bubble, then applying heat to the middle of the patch to draw the solder in from the edges.
Not a pretty job, but I think the solder flowed under the entire patch and bonded to the tank and patch.
if you don’t care if the repair is ugly, Loctite PC 5070 is a water-activated epoxy adhesive combined with a fibreglass filament tape. A heavier duty version is called Rapp-It, Crofton Pulp uses it all the time to fix leaks in their piping systems. Unified Alloys in Langley is the distributor.
Rapp-it may be my next attempt if needed. Looks like an amazing product. The tank is tucked into a tiny closet, so looks not important.
This is just an idea, but I suspect the problem with the silver soldering is that it ends up on the surface rather than wicking into the pin hole. I wonder if you could use a good epoxy and get a tiny bit of vacuum into the tank to suck it into the pin hole. This could be as easy as warming the tank, plugging all the ports and then cooling the tank. Ideally I would use a vacuum gauge so you know what forces you are actually putting on the tank. Maybe a good vacuum cleaner could do it.
On another note, I have a bronze water hot water tank too. It is to be a heat storage tank for the waste heat from my Lister clone diesel. I haven't pressure tested it yet but if it had a leak my first thought would have been silver solder. I wouldn't mind seeing your system sometime.
Chris
I'm sure you are 100% correct about the solder not penetrating the hole. I don't think anything could penetrate the hole without a very powerful vacuum or external force. I do have a vacuum pump, so this approach is within reason.
You're welcome to drop by anytime Chris.
Yes I'd love to see pictures of any of these hot water heater systems, they sound kind of neat.
Here's a sketch of the system:
Cold water from the city enters through the top of the pre-heat tank; the supply pipe actually continues about 2/3 of the way down the inside of the tank and has holes to discharge some of the cold water where the elements would have been installed. Pre-heated water is drawn from the top of the tank and supplies a modern HW tank.
The wood stove is an air-tight, built in fireplace, so it has an outer sheet metal shell, and a thicker steel firebox. There is framing and drywall up to the edge of the outer metal shell. There are refractory castings to line the bottom and sides of the firebox, and 2 refractory castings above to create a secondary burn chamber. When I installed it in the early 90's it was one of the cleanest burning stoves available. I punched holes through the sheet metal case and steel firebox for supply and return water lines to a copper coil I strapped inside the secondary burn chamber. This way I did not have to penetrate the refractory. Except for when I significantly over fire the stove, flames do not touch the coil. Foolishly, I have solder joints inside the secondary burn chamber so I must not use the stove unless there's water in the coil to transfer the heat away. The cooler water in the bottom of the tank flows to the bottom of the coil, and when heated, rises to return to the top of the tank. Convection keeps the water circulating through the coil and tank.
Water from the pre-heat tank feeding the standard HW tank will exceed 160F if I get the fire going too hot for too long. When I get worried about temp/pressure, I enjoy a soak in the tub.
Not shown in the sketch are the expansion tank, temperature and pressure relief valves, drains.
My biggest design mistakes:
- no pan and waste drain under the pre-heat tank. There's a basin to catch leaks but it doesn't connect to the DWV. A major leak would flood the 2'nd floor, and then the main floor, and then the basement...
- solder joints inside the wood stove mean that we can only use the wood stove when there's water in the coil and a tank to capture the heat
So far, I've been OK with the risks, but rationally, I know that the pennies I save would never cover the repair costs caused by a major leak. If I weren't so obstinate, I would remove it and repair the holes in the firebox.
Just remember when the dentist fills a cavity he first enlarges the hole to create clean material to anchor to and often a shape to hold the filling.
Anyone welding that would also likely first open the hole in order to clean up the material for the weld.
I didn't do a particularly good job of cleaning when I tried to patch with silver solder in 2021. This time, I did consider cutting a window in the tank, and then sliding in a bigger patch and somehow holding it in place on the inside while soldering from the outside, but it got too complicated and I was too chicken to cut into the tank. However, doing so would have led to a better understanding of how thick the tank is and how pervasive the deterioration is.
I'm hoping that a better cleaning job, and a patch will be sufficient this time - the pin hole it still there; just covered up with a copper band aide.
Lots of good suggestions.
Can you post a photo of this pin-hole?
In particular I'd like to see the seam that you mention.
How thick is the tank wall?
Here's a pic from 2021 of the original pin hole. I can't feel the water spray until it accumulates enough to form drops. It is as fine as spider web.
The new patch covers that entire crack.
Steve
Clever system to take advantage of your wood heating.
OK, the leak. Do you know what the hole actually looks like under the surface?
Not being smart about it but is it leaking because there's a crack that may propagate or is there corrosion on the inside that has only shown itself so far as a pinhole leak but is actually the thinnest point of an area weakened by corrosion kind of like what you see when you knock the scale off a piece of old rusty steel?
For peace of mind I'd want to know that any fix I did was structurally secure and guaranteed to contain supply pressure with a good factor of safety. I'm seeing city water up to 100 PSI and maybe 60 on a well. Do you know the pressure in your system when the water is hot? I'm thinking of expansion of the water as it is heated. Worst case scenario is scalding hot water erupting from the tank because of failure of a hidden flaw, I wouldn't want you to have to deal with that.
Not saying that the rules apply but there are probably areas in boiler codes (ASME Etc.) that could give an idea what safety factors are recommended for the pressure and temperature combination.
Hope this is useful to you, good luck & be safe!
D
I suspect you're correct that there is a larger crack and the water has found it's first exit point. Hopefully, this patch contains that crack, but I would not be surprised if the crack expands, or another one opens up. The tank came from my father-in-law's 1949 home. I repurposed it about 30 years ago. I don't remember why he removed it. Preventative maintenance maybe, or perhaps insufficient capacity, or conversion to natural gas - I don't recall...
Our household water pressure is regulated down to 75 PSI and there's a large expansion tank that has been handling the heated water, and although it's been a while since I hooked up a pressure gauge, the pressure didn't seem to increase with use.
I can manage another incident of a small leak, but a catastrophic failure would cause a lot of damage... As I said before, it would be prudent to pull it and deal with some minor drywall repair to access the firebox to plug the holes.
A dozen years ago, or so when we had out hydronic heating system updated, I confessed about the pre-heat system to the installer - he was aghast and certain that it would explode. He might be right if we wait long enough. I know this is a redneck hack, and not by the book, and I really hope I'm not back online crying about the mess I've caused in the future.
If you have a TIG welder the cheapest repair is to weld it - if it is a pin hole as you say it is than you do not need any filler material.
Drain the tank.
Make sure to mark the pin hole location.
Clean in very well.
Say tank is very thin, like 1mm or so and the weld is also very thin as well. Start your TIG at just 20 amps and see how it goes. Go in increments of 5 amps. For welding 1mm bandsaw (so steel) in the middle I need 25 - 28 amps and for the edge I drop to 20 or even 18. Since your stuff is just a pin hole its like 100x times easier job, just point TIG torch at it and as soon as you see tiny melt pool stop. Done.
Note that bronze or copper or similar will require more amps than steel due to better heat conductivity - but still start low. There is nothing to be afraid of - in the unlikely even of a screw up & inability to fix it - you can fall back on many ideas above.
Thanks so much for the advice and parameters
@Tom Kitta. I'm a crappy MIG welder, and have very little time with the TIG, and no satisfactory results with it yet. I have some 1 1/2" copper pipe that I could practice with by welding on patches. The TIG process looks like it should be so easy, but I get so frustrated with myself when I screw it up. MUST PRACTICE!!!
Again, thanks everyone for your wisdom and suggestions. I also very much appreciate the safety concerns, even though I carry on a bit recklessly.
Ok stop throwing stuff at me...
