Leaking Central Boiler OWB

Jon E · Jan 4, 2016

Started a new thread because the others on this subject were pretty old. My CB 5648 (built 2004) is leaking and I am looking for a way to chase down the leak. I am getting water dripping underneath the pump area. It's enough where the water level drop is noticeable over a shorter time period than 'normal'. I did put a new zone and pump on the unit this past summer but I did not re-insulate the area and it is visible - and not leaking from that area. I hate to scrape off all of the foam insulation around the water jacket but I am concerned that the drips are taking a path of least resistance - the leak might even be near the top of the unit or on the other side for all I can tell.

Has anyone had success with a thermal imaging camera? I am curious if I could track the leak that way somehow. There are also mixed opinions on boiler leak-stop liquids such as the Hercules or Gunk products. I have Taco 007 pumps, which are water-lubricated, and a Taco plate exchanger which was big $$$; don't want to gum up either one if I can help it.

I've also read about CB's rather crappy customer service and repair policy. The unit is now 12 years old and I don't remember what the warranty is. I did have my door replaced last year and that took months and I had to pay the shipping fees.

NSMaple1 · Jan 4, 2016

Well - I know some people talk death on the Stop Leak stuff. But I used it with great success.

I did my system over 3 years ago (going into winter 4 now), and when all was said & done I had a couple or three niggling drips from threaded connections that would have meant taking apart multiple connections in tight spaces with big wrenches in order to try fixing them. So, I got 4 bottles of the Gunk stuff. I had to order it & didn't know how much I would need - my system holds around 700 gallons. Had a Grundfoss 15-58 3 speed circulator for my zones, situated down low pumping towards the boiler. Also had a stub with a valve & plug on it just upstream of that. I got things warmed up & circulating by convection, then poured a bottle in the stub. Shut valve & let circulate by convection for a couple hours. The Gunk had to flow thru the pump to get to the leaks, but the leaks were not far downstream of the pump. They stopped almost immediately. Haven't leaked since. I have since swapped that circ out for an Alpha, but the 15-58 was still working fine when I did the swap and it's on the shelf for a spare. I also have a 20 plate HX in the system for DHW. And another 15-58 for my boiler pump. No problems noticed with any of them. I did have the boiler pump stick on me at startup this fall, but not sure why. It did sit all summer whereas I had burned all summer for DHW the past couple of years, and it has been 3 years since I added the Gunk. This is on an indoor pressurized system so not sure what the results would be with an open system OWB. The way I looked at it, if it worked and ruined my 15-58, the cost of a new 15-58 was way worth it compared to all the work I was looking at to take apart & reassemble all that piping.

Thermal camera might help you find it, depending where the leak is & how the water is seeping. I would not count on any help from Central due mainly to the age, I suspect you are completely on your own. Also suspect the leak might most likely be close to the water line up top - but that's just a wild guess.

Good luck.

cantoo · Jan 4, 2016

Any way to pressurize the boiler with air and then you might have a chance of hearing it? I bought a used Pacific Western and I put a couple of line caps on it and pumped it up with air to see if it had any leaks. It leaked around the top filler so I put the air to it and the only place I could hear a slight hissing was the filler tube. Been 3 years now and no leaks.
It might help you to find a place to loo at least.

windthrown · Jan 4, 2016

Did you keep the rust inhibitor up to snuff? CB has some of the best anti-corrosion additive out there. It has to be replaced every 3 years though. I would avoid adding any leak plugging stuff as that will just plug up your heat exchangers. CB has (or had) a 25 year warranty against tank leaks when we installed our Classic model. Dealers vary as to how well they uphold the warranty. Our dealer gave us a new controller and anti-rust stuff for no cost when the controller failed and we had an overboil.

I would scrape the foam off in small sections one at a time and look for the leak. Most likely it is a corner weld. You can buy a can of high density foam and patch the insulation back up real easy. Pressurizing the system to find the leak is hard because they are open systems.

Iska3 · Jan 4, 2016

I think cantoo has the right idea. Do you know any good plumber? I worked with a few plumbers over the years and when we did a make over on a 8 unit apartment building, we had to do a pressure test of the plumbing system. Some of the plumbers have rubber plugs in many different sizes so they could plug a main drain, a stool or even a sink trap. Some of these rubber plugs have a gauge or even a air type do-hicky thing like on a tire; they can pump air in to the system and find a leak... If you could find a plumber that his some of these plugs, you could plug off your top vent, turn off your in and out water lines and fill the system with air. One time we found a bad PVC "T" that in between a wall, (it had a sheet rock screw going in the "T")... The plumber filled the lines with 3 # air and then took a short piece of PVC pipe to his ear and kept working along the walls until he could hear a slight hiss. It's worth a try...

Start at the top of the water jacket and work your way down.. Someone once wrote on a site that his CB had rusted out around the overflow and the tank, something to do with a bad seal around the overflow and the roof and let let the rain water in over the years.. Hope this helps....

cantoo · Jan 4, 2016

Yup, I've heard of guys finding leaks up high at the fill spout and just not putting as much water in the tank as a short term solution. As windthrown said I also wouldn't put anything into the lines or the exchangers. The leak is in the OWB so jerry rig the hoses so you are only working with the OWB. I knew a guy that had the same stove as mine and he had a leak at the door frame. He was adding gallons of water every other day, he ended up using silicone and it plugged it enough that it held water. Much cheaper than replacement.
What I would do on my OWB if I still couldn't find the leak after trying to airtest it is.
- disconnect the supply and feed lines.
- put a ball stopper inside the fill tube pipe out the top (on mine this is how it is filled)
- connect garden hoses ends onto those water lines. T one of the lines and plumb an air hose fitting on it so I could pressurize the tank.
- buy a cheap electric drill powered pump that has garden hose ends on it.
- pour the leak sealer (bar's leak, gunk or whatever you feel will work) into the garden hose end.
- hook the drill pump onto it and start recirculating the water.
- after 10 minutes I would put 10 lbs of air into the air nozzle and keep pumping with the drill.
- another 10 minutes and put some more air in.
The air will help force the sealer into even small holes because if you have 1 you likely have more. If your pump is at the OWB then make sure you bypass it too. No use maybe causing a problem to it.

Jon E · Jan 5, 2016

Thanks for the responses, guys. Did not think of air testing it, I am sure I can rig something up in the spring to run an air test if I don't find the leak by then. I'm pretty sure it's near the bottom of the water jacket.