I have a fairly new on demand water heater that somehow got a crack in the copper pipe that coils around inside the unit. It is not possible to cut the bad place out and solder in another piece. After draining the lines, sanding and cleaning the pipe with acetone, I used JB weld. It lasted about 2 weeks and now I have the same problem again in the same place. The water began seeping from under the weld and runs out the edges of the weld. I took a drimmel and sanded off the weld that was over the crack. Does anyone have another suggestion than using the JB weld again. I can't afford to replace the water heater. Thank you

I have in the past repaired a cracked water line in a commercial ice machine by brazing the split. I would check to see if this is covered under a manufacturers warranty. How old is the heater?

How about a picture of the area using "Go Advanced/Manage Attachments"

My husband bought it about a year and a half ago. He installed it in our remodeled barn for game room/bed/bathroom, we built in the upstairs of the barn. My husband became ill and died Until this winter, it had never been used much. It is being rented out now. I am trying to do things on my own but it is difficult. He was the one who purchased it and I have no idea about the warranty and even at that, I probably messed that up since I used JB weld on it. I'm sorry but I'm not familiar with the procedure you mentioned. Would it withstand the temperature of the hot water pipe? My husband was such a wonderful guy and he was so knowledgeable at being a DIYer. I've learnt a lot from him but so much of this is over my head, but I'm willing to learn.

I'm very sorry for your loss.

Yes, brazing will withstand the heat but it is not exactly a beginner process. Also it requires specific equipment.

If you contact the manufacturer with the model number and the serial number they will be able to tell you if it is still under warranty. Chances are that it is. I would go this route first and foremost.

Brazing is also called silver soldering. Air conditioner lines are silver soldered primarily because of the high pressures involved. Silver soldered pipes are extremely strong.

At a minimum you need a MAPP gas torch, Oxy acetelyne will work and so will oxygen - MAPP.

You need a clean pipe, flux and silver solder and a torch big enough to heat the pipe. You may need one that's maneuverable as well. That's part of the reason to post a picture.

Silver soldering is a skill and practice will be required.

These heads + a <$20 disposable cylinder is probably the cheapest method. TurboTorch Extreme Self Igniting Propane/MAPP Torches (http://store.cyberweld.com/exselito.html)

You won't have maneuverability in a cramped space.

MAPP gas will work but make sure you have a MAPP gas torch head and NOT a propane head on a MAPP cylinder. Keep in mind that brazing or silver soldering ARE NOT THE SAME AS SOFT SOLDERING. I say that not for sake of argument but in case any other user has a similar problem and considers doing this type of repair with normal soft soldering. Also and type of weld you decide upon you will need to evacuate all water from the pipe beforehand. And as K.I.S.S. mentioned, brazing is a skill. I am an HVAC/R technician and I have brazed more pipe then I care to remember and my first attempts were a trainwreck. Even today, after 5 years I still have some welds that are difficult. Again I urge you to contact the manufacturer with the info on the unit. It could very well be a factory defect. I have seen brand new, out of the box copper line sets develop a crack due to a factory defect.

Thank you both so much. I did read and watch a video on cutting out the area, using flux and soldering in new. My husband does have a propane torch, not sure if that is as good. As most everything around here, my digital camera quit working on me, so the pic is out for now. It is in tight quarters. I know that my husband purchased the heater at our little hardware store in town which they had to order. I will go in tomorrow and check with him and see if he knows anything about the warranty. I'm just afraid because I messed around with it, the warranty won't be any good. Plus, I really can't wait that long to replace the whole unit since I'm renting it out. If I hire a plumber, do you have any idea what it would cost me? Thanks again

In addition, MAPP gas doesn't work very well on pipe larger than 3/4" refrigeration pipe, which would be 5/8" plumbing. I've never seen 5/8" plumping but I'm not a plumber either :D.

Thank you both so much. I did read and watch a video on cutting out the area, using flux and soldering in new. My husband does have a propane torch, not sure if that is as good. As most everything around here, my digital camera quit working on me, so the pic is out for now. It is in tight quarters. I know that my husband purchased the heater at our little hardware store in town which they had to order. I will go in tomorrow and check with him and see if he knows anything about the warranty. I'm just afraid because I messed around with it, the warranty won't be any good. Plus, I really can't wait that long to replace the whole unit since I'm renting it out. If I hire a plumber, do you have any idea what it would cost me? Thanks again
Propane is not the same as MAPP. Depending on where the section is it may or may not work. I wouldn't ask the hardware store guy about the warranty. If he had to order it then it may not be a common unit that he stocks and he may not know much about it. I would bypass the store and contact the manufacturer. In my line of work when I have a question as to the warranty I go straight to the manufacturer. They have all those numbers on file and have much more info available. I would worry more about replacing the section voiding the warranty then the JB weld.

Cake compared to sealing stuff in quartz tubes under vacuum with a Hydrogen Oxygen torch. You basically collapse the tube onto itself and hopefully seal both ends without letting air in. Fun.

My first attempts at MIG, TIG and stick were good too.

Silver soldering is VERY different than soft soldering.

Note that those torches aparently handle MAPP and Propane.

Note that those torches aparently handle MAPP and Propane.
Yes. MAPP heads will accept propane and propane heads will accept MAPP cylinders but MAPP burns hotter. That and the head is designed differently.

And to clear up something, unless you have a small holding tank you do not have On-Demand hot water. You simply have a tankless water heater. Nit picking I know but it is a pet peeve of mine... one of many apparently.

Soldering and Brazing:

Copper.org: Plumbing: TechCorner - Soldering and Brazing Explained (http://www.copper.org/applications/plumbing/techcorner/soldering_brazing_explained.html)

I appreciate both of your advice. I can certainly tell this one is over my head and beyond my skills. I'll check with the manufacturer tomorrow as you suggested.
Sites like this have been a big help to me since my husband passed away. I was able to change my back brakes in my Yukon, and take off, clean and replace a jet in the carborator of my moped that had sat for a few years and gunked up. I had it running nicely before the summer was over. I couldn't have done it without help from guys like you.

5/8 refrigeration would be 1/2" copper

Copper.org: Fuel Gas: Table 2 - Dimensions and Physical Characteristics of Copper Tube: Types K, L, ACR and Gas (http://www.copper.org/applications/fuelgas/fgtables/table02.html)

5/8 refrigeration would be 1/2" copper Grade K and L

Copper.org: Fuel Gas: Table 2 - Dimensions and Physical Characteristics of Copper Tube: Types K, L, ACR and Gas (http://www.copper.org/applications/fuelgas/fgtables/table02.html)

5/8 refrigeration would be 1/2" copper Grade K and L

Copper.org: Fuel Gas: Table 2 - Dimensions and Physical Characteristics of Copper Tube: Types K, L, ACR and Gas (http://www.copper.org/applications/fuelgas/fgtables/table02.html)

Yes I know that. I said 3/4" refrigeration.