Water heater condensation

[os1kne]

I have a gas water heater in my basement. For the past couple of months, after most uses of a large amount of hot water (shower, dishwasher, laundry, etc.) condensation will drip from the "exhaust pipe" for the water heater (the vertical portion which runs from the basement to the roof). The vertical part of the "exhaust pipe" looks to have an asbestos coating on it, so I don't want to mess with it much. I know that the water is not rainwater, as I've been on the roof and established that the top is okay.

I assume that this is "just" condensation from the hot exhaust hitting the cool outside air, but when there's a cup or more of water dripping - it gets to be a problem. For now, I've got a bucket hanging under the problem. Is there a better solution?

Thanks.

[LCHIEN]

I have a gas water heater in my basement. For the past couple of months, after most uses of a large amount of hot water (shower, dishwasher, laundry, etc.) condensation will drip from the "exhaust pipe" for the water heater (the vertical portion which runs from the basement to the roof). The vertical part of the "exhaust pipe" looks to have an asbestos coating on it, so I don't want to mess with it much. I know that the water is not rainwater, as I've been on the roof and established that the top is okay.

I assume that this is "just" condensation from the hot exhaust hitting the cool outside air, but when there's a cup or more of water dripping - it gets to be a problem. For now, I've got a bucket hanging under the problem. Is there a better solution?

Thanks.

can you route it to your drip pan below your water heater?

[docrowan]

I wonder if insulating the exhaust pipe (with something NON combustible) would help.

[os1kne]

No drip pan below the water heater, but I do have a floor drain near the water heater - I suppose I could get a big funnel and some pvc (or garden hose) and rig up a solution. It wouldn't be very classy, but it would keep the floor dry.

Insulating the pipe sounds like it might help, I can access about 70% of its length, with the inaccessible portion being near the middle.

Thanks. I'm open to more suggestions.

[master53yoda]

I have a gas water heater in my basement. For the past couple of months, after most uses of a large amount of hot water (shower, dishwasher, laundry, etc.) condensation will drip from the "exhaust pipe" for the water heater (the vertical portion which runs from the basement to the roof). The vertical part of the "exhaust pipe" looks to have an asbestos coating on it, so I don't want to mess with it much. I know that the water is not rainwater, as I've been on the roof and established that the top is okay.

I assume that this is "just" condensation from the hot exhaust hitting the cool outside air, but when there's a cup or more of water dripping - it gets to be a problem. For now, I've got a bucket hanging under the problem. Is there a better solution?

Thanks.

post a picture of thewater heater flue piping as what you have discribed could be a incorrectly piped flue. If this is not the case below is typically what the conditions are.

The drip that occurs during firing when the tank has refilled with cold water is the flue gases condensing on the heat exchanger tube inside the water heater. The main product of combustion for natural gas or propane is CO2 and water vapor. The heaters are designed when above 100 degrees to keep the flue gas temperatures above 300 in order to prevent condensation in the heat exchanger. Insulating the exposed piping will not affect the condensation that you are experiencing. Also do not block in any way the draft hood on top of the water heater that is the flue connection.

The solution to this problem is to provide a large enough water heater so that the heater meets your families water needs without the water getting cold. In many large homes two heaters are paralleled to provide higher capacity or a larger / higher input heater can be used. Neither of these solutions are inexpensive.

There is another alternative but requires a plumbing modification and that is to install a tempering valve on the system that will mix cold and hot water to provide the water to the building. The water heater is run as hot as possible and the heater output is mixed with cold water to reduce the house supply to 130 degree range. the water heater could be running at has high as 175. this provides about 30% more 130 degree water then you are currently getting
Watts 70A Hot Water Extender Tempering Valves Series Watts 70A, L70A Hot Water Extender Tempering Valves are used in residential water supply applications to mix cold and hot water to extend capacity of water heater storage tanks and hot water boiler tankless heaters. It features brass body construction, dial adjustment cap, replaceable thermostat, stainless steel spring and is available with either threaded or solder end connections.

The L before these Watts 70A Valves signifies that the valve is low temperatrure.

[os1kne]

Art,

Thanks for the response. It is a 50gal high-efficiency water heater, a little over 2 years old. Here's a pic of the flue, you can see the water stain running down the wall. (It's not pretty, but I suspect that these things usually aren't.)

Please let me know what you think.

[Daryl]

Is your flu pipe single wall? I think if you used double wall pipe to the roof there would be no hot air hitting the cold. Have you done any recent work around the flue or in the area of it that could of brought on the problem?

[just started]

I think you have a restriction of some type in the flue up near the roof. There was an "Ask T.O.H." episode about this type of problem that I saw about a month ago.

[n2go]

water heater condensation

In my area there are recommendations for vent pipe diameter. A couple years ago I replaced my furnace with a 97% efficient gas furnace. It uses a plastic air intake and a plastic pvc exhaust pipe out the side of the house. I had my 50 gallon gas fired water heater exhausting to my chimney. Unfortunately this would no longer work since the flue gases would no longer be hot enough to exhaust out the chimney. They would cool and condense and their acidic nature would ruin the brick chimney. I had to use a liner to reduce the flue pipe to 4 or 5 inches. I used flexible pipe for about 8 feet and the rest I used insulated steel pipe. This keep the flue gases warm enough to exit the chimney. Since then I have replaced the water tank with a suit case sized "demand type water heater". The gas only turns on when the water water faucet is turned on. This is done by a pressure switch.
That heater is mounted on a side wall of the house and requires a 4" stainless steel vent pipe sloped downward toward the outside. By the picture supplied it looks like the flue gases are condensing it the pipe and dripping down the pipe. My observation would be that the pipe is too large a diameter. If the pipe were insulated it might work. Check local code.

[n2go]

water heater condensation

After looking once more at your setup I have to add a few comments. There is carbon monoxide in that pipe. If the acidic condensation continues it will cause the pipe to rot and leak gases.
Look into dropping a flexible stainless or aluminum pipe (depending on code) into the pipe on the roof and feed it down to the flue pipe at the heater. The smaller diameter pipe should solve your problem. higher efficiency heaters or furnaces mean that less heat escapes through the exhaust. Smaller diameter flue pipes are needed to let that steam( white smoke) escape without condensing in the pipe.
My high efficiency furnace uses a pump to get rid of the water at the furnace...
I am glad you supplied the picture. Fix this situation or place a carbon monoxide detector near those pipes.

Jim

[chrisk]

Is the water heater a power vent (fan assisted exhaust) unit? If its a considerable horizontal run (more than a couple feet) without the fan, it may not be exhausting properly.

[os1kne]

Thanks for all of the replies. I'll try to answer the questions that have been posted. The flue pipe appears to be a metal pipe inside some sort of (asbestos?) coating/insulation. The bottom of the metal pipe is probably about 6", it must get reduced because I don't believe that it's that big on the roof, though I haven't measured. It runs vertically about 25' to the roof through a "chase".

On the other side of the exhaust, is the wall between the house and the attached garage. Several months ago (when it was warm), I cut out a section of the garage side of the wall to facilitate running some electrical wires. I didn't think much about it, but it's probably contributing to the problem - cold air from the garage is able to surrond the pipe within a few feet of the bottom. I should probably patch the hole asap.

The horizontal run is about 3 feet, no fan for assistance. I have a CO detector near the water heater.

I appreciate all of the replies. The more I read, the more I think that there are multiple issues to address. I'll be digging out the manual for the water heater to double check the exhaust recommendations.

[master53yoda]

In my area there are recommendations for vent pipe diameter. A couple years ago I replaced my furnace with a 97% efficient gas furnace. It uses a plastic air intake and a plastic pvc exhaust pipe out the side of the house. I had my 50 gallon gas fired water heater exhausting to my chimney. Unfortunately this would no longer work since the flue gases would no longer be hot enough to exhaust out the chimney. They would cool and condense and their acidic nature would ruin the brick chimney. I had to use a liner to reduce the flue pipe to 4 or 5 inches. I used flexible pipe for about 8 feet and the rest I used insulated steel pipe. This keep the flue gases warm enough to exit the chimney. Since then I have replaced the water tank with a suit case sized "demand type water heater". The gas only turns on when the water water faucet is turned on. This is done by a pressure switch.
That heater is mounted on a side wall of the house and requires a 4" stainless steel vent pipe sloped downward toward the outside. By the picture supplied it looks like the flue gases are condensing it the pipe and dripping down the pipe. My observation would be that the pipe is too large a diameter. If the pipe were insulated it might work. Check local code.

I missed catching this thread again. Looking at the flue that is coming down the wall it appears to be 6 or 7" B-vent If the water heater is the only appliance on that vent it is to large and not drafting properly. if the outlet on the water heater is 3" as it appears to be the main stack should only be 4".

also the 3" vent looks like it is dead horizontal. if it is more the 1' to to 18" it won't draft correctly. Pleas take a picture of the top of the water heater and a picture between the water heater and the main stack. It appears that there are a number of issues with the flue piping.

[os1kne]

Thanks for the reply. I'm away for a few days, so can't take a pic. The 3" does have a rise to it. I believe the manufacturer specified at least 1/4" rise per foot, and I know that it's at least that. (I recall paying close attention to that when I put the water heater in.)

I suspect that the flue may have originally handled the furnace in addition to the water heater. The home is about 45 yrs. old, the furnace was replaced ~ 15 years ago with a high efficience furnace (vents via PVC out the back of the house). I was able to download and look at the manual for the water heater - all that is specified is that the flue be a min. of 3inches in diameter - it's definitely much larger than that.