Furnace question

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I have recirculating hot water for heat. There is an expansion tank and an automatic air vent above it. I am getting a slow leak of water from it. Like a drip once in a while. I put a small tin under it, and keep an eye on it, figuring it would go into summer and get fixed when I have the system cleaned. Well I just looked and there is more water all of a sudden. Guess I put it off too long. I plan to go away for the weekend; anything I should do, so I don't come home to a flooded basement? I do not think I can replace these parts (both are bad), and I doubt the biz that I use for service can get to it this week (but I plan to call tomorrow).
 
You either have to replace the fittings or dissasemble them and re tape and install. If it's a crack in the tank out will have to be welded or replaced. a pic would be nice cause you are not very specific. Im a maintenance tech for a bunch of apartments that have huge Boiler systems and they are pretty much the same as your setups.
 
Shut down the boiler and the water supply to the expansion tank that supplies it with water.
There should also be valves to isolate the boiler from the distribution piping, so close them as well.
There should then be no worries about more than minimal leakage.
When you return, just open all of the valves, since in NH you'll probably still need heat.
Fix everything over the coming summer.
 
you could preemptively drain the system. I do that but my hot water system is plumbed into mains so it makes it really easy. if you did that it would also save a step for the tech who has to come out. mine has a standard hose fitting so all I do is hook a garden hose to it run it into my Mud sink open the valve and crack open the highest fitting on my radiator. if your system is anything like mine you might have to go and buy a special key
 
The technical term for it is boiler not furnace.

Given it is not that cold you can simply shut off the boiler(emergency red switch) when not home. Is it possibly your pressure relief valve is sticking? It likely only drips when the boiler is hot.

You can also shut off the water supply to it (gives system pressure to lift water to upper floor(s)) in case it still leaks when off.
 
The automatic air vent is probably crudded up with hard water deposits and just needs to be replaced. Why do you think the expansion tank needs replacing? Usually its a bladder tank and you replace it when the bladder goes. It should have a small valve like a tire has. If you quickly press it in and let go, air should come out, if water does, then the bladder is shot. Maybe a good idea to add some air to the expansion tank. You can replace the air vent yourself. But you will need to shut down the system, isolate the distribution section from the boiler. Shut off the feed to the boiler, Then let some water out to eliminate the pressure. At that point you should be able to replace the air vent without too much trouble, but I would have the new one wrapped with teflon tape ready to go.

Turning off the boiler and feed will prevent a lot of water from leaking.
 
I agree with Donald. If you can depressurize the system and get to the air valve try the following. Use CLR or vinegar and clean the valve. You can soak the valve and then rinse it off. You can also use an old toothbrush dipped in CLR or vinegar, wear eyewear. If you can't remove the valve soak some toilet paper in either liquid and wrap it around the valve where you see buildup. This should loosen the buildup.
 
I emptied the pan (that was catching the drippage), and the furnace cycled twice; no water. I think I am over reacting. With the temp rise, I bet the basement humidity is rising,and the pan is not evaporating off as fast.

The vent is crusty, and is in need of replacing. Been replaced at least once, if not twice in the ten years I have been here, and the expansion tank once. The last time the service guy showed me how to check the air pressure in the expansion tank. When I went to do that a few months ago, when the leak started, blackish water came out of the schrader valve. I am assuming it is kaput.

Have to leave the heat on for now, our bird would not like it. He would go with us but he does not like to travel, and we do not have space. But I will contemplate that, turning the system off while gone.

Will call tomorrow. Hot water is off the boiler and so it has to run pretty often.
 
Ah, I see some responses while I was typing. I will look at cleaning it tomorrow, but as said, the expansion tank is bad. I think that is why the vent wants to weep.
 
The bladder in the tank usually has a schrader valve so you can check pressure. Do so. If water comes out during the check, the membrane is shot. If there is air in there, ensure the pressure is to spec. Then consider replacing the valve.
 
I went and cjecked this morning. No water leaked out.

I went and pressed on the schrader. Pressurized water comes out. I say kaput.

Is their a one way valve after the four way junction? I see how I can cut water to the boiler, but I am unsure if their is a one way valve to prevent the baseboards from draining.

On the good side, I should be able to see my uncle who does HVAC this weekend. (I'd get him to do the job, but he lives 220 miles away.)

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if it's the hy-vent see pic below,
if you push on the valve then yes pressurized water will come out,
it's supposed to vent air automatically and not leak water out,
if you burped water out of it manually that might have been enough to clean sediment out and now it's sealed and not leaking.
they are a $10 part and easy to replace, hard part is when you can't isolate that area and end up having to drain a lot of water out or make a mess swapping a new one in.
if you do end up draining the system, if there's any age on it drop the expansion tank and check that it hasn't failed and is full of water. when the bladder goes inside it, pulling the air valve out of the expansion tank water rarely ever comes out because the bladder seals over that 1/4" diameter hole. that size expansion tank is only $20, so if there's any age on it (over 7 years) given the labor involved consider replacing it.

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Finally had it serviced today. Surprisingly little soot in the system, some sludge in the fuel filter though. Was shocked to realize I had let it go for five years... oops!

One Extrol 30 tank, one blowoff and two vents, a nozzle and filter, cleaning and efficiency test. $353 and change.

Expansion tank had failed, and the blowoff was suspect, as it was not venting.
 
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