View Full Version : Furnace water leak ?

April 3rd, 2006, 06:24 PM
Water is coming out of mky furnace. After everything dried up around the furnace,I found out where the water is coming from.There is a relief valve pipe coming down the side of the furnace.I assume there is a pressure problem could the pressure valve be no good? Thanks for any help on why this is happening,Vin

Mr T
April 3rd, 2006, 06:37 PM
What kind of furnace?
Gas, electric, oil, heat pump, hot water heat?

April 3rd, 2006, 06:46 PM
Hi Mr T.The Furnas is a Burnum oil furnace with an 50 gallon Electric water heater next to it.

Mr T
April 3rd, 2006, 07:43 PM
I'm not a furnace junkie, hopefully others will post in too...

First question.. Are you sure its not coming from the water heater? The heater has a expansion valve for pressure/temp overload. They sometimes can leak. Put a bucket under your overflow tube if you can and see if anything is dripping into it. There also is a drain valve often hooked into the cold inlet. Check that too for leaking. If the heater is old, it could be about to 'rot' through. Check around the edge along the bottom seal of the heater casing. If it appears wet, be prepared for a flood and get that thing replaced fast. (dont go away for long periods of time)

You can also put a few pieces of cardboard down around the floor to see if any of them get wet. It may tell you where the water is coming from.

Does it smell like fuel oil?

Unless this is a hot water furnace, there shouldnt be any water piping hooked up to it. I am not sure about modern oil furnaces (this doesnt too new...is it?), but modern (90% and up) gas furnaces have a condensate drain tube (2 if you have AC). There is a trap and sometimes a filter on the furnace one. If this tube gets plugged up, it will overflow.

April 3rd, 2006, 09:32 PM
Vin stated that it is a "Burnum oil furnas". Actually Burnham makes hot water boilers (and steam boilers too,but sounds like this is a hot water boiler).Boilers do indeed have relief valves and they can trip on overpressure,and they can also fail.It needs to be checked to see if it just doing what it is supposed to or if it needs to be replaced.

April 3rd, 2006, 09:35 PM
I do have a vent valve above the expanshion tank and it was dripping. I repaced the inside part and it's good now.The furnace has a pressure valve on it with a little lever instead of a knob. I lift up on it and it makes water come out a vent pipe on the side of the furnace. I put a soda bottle under the pipe last night and today it was full.So I now know where it is coming from but,I don't know why.

April 4th, 2006, 02:20 PM
It sounds like from what you are describing, that you have one of those small expansion tanks above the boiler. Probably one of those camper propane tank looking ones, perhaps? If somehow something happened to the bladder inside and you have lost air pressurre...what hapens is that when the boiler tries to heat up the water, the water expands and makes the water pressure climb. (And this should not happen any more than perhaps the water pressure going up a couple or few psi) Boilers are equpped with usually 30 psi pressure relief valves. If there isn't sufficient air in the expansion tank, then the pressure can approach that 30 psi and cause the pressure relief valve that you have leaking, to leak.

I recently had this senario on a boiloer, just like you. Found when I took a tire pressure gauge check at the bottom valve stem of that expansion tank that it registered 0 psi, even though there was water pressure in the boiler! How could that possibly be, you may ask? Well, the bladder collapsed around the valve stem and blocked any of the water in the tank above it from exerting static pressure at that tire-like valve stem. I removed the core out of the valve stem with one of those cap covers you can get at auto parts stores that also can unscrew valve stem cores, and I poked, gently up inside with something that wasn't pointy and I got the bladder unstuck after I let water out of the boiler to relieve the pressure. Then I put the core back in the valve stem and aired up the expansion tank to 12 psi, (which they are normally factory set at). I later checked the pressure and it was holding at 12 psi weeks later.

Regardless, whether you have my exact problem or not. It could be due to a weak pressure relief valve. It could be from a water logged expansion tank. Or, it could be from a boiler whose water temperature is being over exceeded.

Do you have a temperature/pressure gauge on your boiler. It should have one factory built in. What do these read when it is cold and what does it read when it warms up? If expansion tanks are water logged (they are supposed to have air in them) is that the water pressure significantly goes up when the water is heated, compared to the low reading when the boiler was cooled down. If it goes from like 12-18 psi cold, to 25-30 or more hot, then it is definitely the expansion tank that is water logged.