# Boiler loosing pressure



## Jon59901 (Dec 8, 2013)

Ok guys I'm at my wits end on this one. Today I go to service a Weil McLain ultra. It's running fine no complaints from the homeowner, just yearly service. I shut the boiler down as I always do, pull the jacket off to get a good look and I see aluminum shavings in the condensate drain. Ok easy enough it needs inhibitor added before we loose the heat exchanger. I empty the drain and re-attach it. Next I isolate the boiler from the system to check for pressure drop. Sure enough within two minutes my pressure drops from 15# to 0. I start looking for leaks. None in the housing none on the floor. I open the valves to the system and the pressure comes up to 15 then I isolate again. Sure enough pressure drops again. No water coming out of the condensate no leaks anywhere. I even shut off the fill valve thinking maybe somehow it's pushing back into the fresh intake. Nothing. There are no visible leaks on this thing anywhere. I'm at a loss. The boiler is completely isolated and I'm loosing pressure with no leaks. The other weird thing is there is a separate pressure gauge on the boiler side of the isolation valves that lost pressure at the same rate as the one on the boiler. The only thing I can think of is.....Christmas miracle? Anybody have a clue?:huh:


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## rjbphd (Feb 5, 2010)

Jon59901 said:


> Ok guys I'm at my wits end on this one. Today I go to service a Weil McLain ultra. It's running fine no complaints from the homeowner, just yearly service. I shut the boiler down as I always do, pull the jacket off to get a good look and I see aluminum shavings in the condensate drain. Ok easy enough it needs inhibitor added before we loose the heat exchanger. I empty the drain and re-attach it. Next I isolate the boiler from the system to check for pressure drop. Sure enough within two minutes my pressure drops from 15# to 0. I start looking for leaks. None in the housing none on the floor. I open the valves to the system and the pressure comes up to 15 then I isolate again. Sure enough pressure drops again. No water coming out of the condensate no leaks anywhere. I even shut off the fill valve thinking maybe somehow it's pushing back into the fresh intake. Nothing. There are no visible leaks on this thing anywhere. I'm at a loss. The boiler is completely isolated and I'm loosing pressure with no leaks. The other weird thing is there is a separate pressure gauge on the boiler side of the isolation valves that lost pressure at the same rate as the one on the boiler. The only thing I can think of is.....Christmas miracle? Anybody have a clue?:huh:


Where's the expanison tank located and piped?? Alum shaving in cond drain is on the fire side of boiler, inhibitor will only take care of on the water side.. take some pictures..


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## MootsNYC (Dec 19, 2013)

Have you checked the automatic air vent?


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## Jon59901 (Dec 8, 2013)

MootsNYC said:


> Have you checked the automatic air vent?


I have, it's doing just fine. It is on the primary so it can't be a factor when I isolate the boiler. There is a pressure gauge on the primary which holds when I isolate so I know the system isn't loosing pressure. It's somewhere in the boiler but without any visible leaks I can't figure out where.


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## Jon59901 (Dec 8, 2013)

rjbphd said:


> Where's the expanison tank located and piped?? Alum shaving in cond drain is on the fire side of boiler, inhibitor will only take care of on the water side.. take some pictures..


The expansion tank is on the primary, though it is undersized. The pressure in it is good so I know the bladder is holding. But it also is separated from the boiler when I isolate it. My biggest concern is that I need to put glycol in the system but I need to find this leak first or there's no point pumping glycol in it. I opened the drain on the heat exchanger and sure enough, it was beautiful clean clear water. So I know it has a problem somewhere.


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## CTs2p2 (Dec 6, 2011)

I've changed two Ultra heat exchangers that were leaking right in to the condensate pump.

Try adding a little food coloring to the boiler water you'll see it in the condensate I'd bet. 

With the expansion tank isolated, it's only going to take a shot glass full of water to lose your pressure.

Did you notice any signs of moisture in the fire side? Maybe it's a small enough leak it's steaming off and heading out the vent.


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## newyorkcity (Nov 25, 2010)

Is there an indirect water heater on the system?
Are you sure there is no heating pipe running underground?


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## Plumbworker (Oct 23, 2008)

Doublewall heat exchangers? check the weepholes


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## MootsNYC (Dec 19, 2013)

newyorkcity said:


> Is there an indirect water heater on the system?
> Are you sure there is no heating pipe running underground?


 He isolates the boiler with the house side, I thought the same thing at first.


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## Jon59901 (Dec 8, 2013)

Thanks guys for all the advice. I haven't been back to the house since the other day. Hopefully they will call so I can figure this thing out. As of now they are going to "talk it over". He said they'll let me know soon. :icon_rolleyes:


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## Jon59901 (Dec 8, 2013)

newyorkcity said:


> Is there an indirect water heater on the system?
> Are you sure there is no heating pipe running underground?


No indirect water heater. Get this, they have an AO Smith cyclone right next to the boiler. Makes a lot of sense doesn't it. I tried to get them to swap it for an indirect, but no luck. There are heat lines in the slab, but when I isolate the boiler, there is nowhere for the water to go.


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