Water Heaters - Cold Weather Flue Pipe Problems

I have a new Rheem natural gas atmospheric venting water heater that was professionally installed by a local plumbing contractor in September of this year. The flue vents perfectly when the temperature is above 45 degrees. However, when the temperature is below 45 degrees it takes the flue too long to vent and the tank becomes so hot that the plastic caps by the hot and cold water nipples actually melt. However, if the burner kicks back on a short time later while the flue is still warm it vents just fine.

We have a two and a half story house and the flue vents about a foot above the roofline. The flue has to go horizotnal in a crawl space before going outside and there is an elbow, but the plumber says the horizontal pitch is fine. Plumber says a draft inducer would solve the problem, and says we need to find one that we can turn on only as needed when the weather is cold. However, the only after market draft inducer we can find is a Tjernlund but the fan blades would obsturct the flue when not in use so it would need to be constantly operating and wouldn't last long. Told we need a draft inducer that resembles a blower and not a fan but can't find one yet. Any suggestions?

Why is the plumber telling you that YOU need to find a draft inducer to correct the problem? I would be insisting that the plumber who installed the water heater approx. two months ago make it right. This is an unsafe condition that the plumber should be responsible for. That heat build up, aside from melting plastic caps, is backing up exhaust into the house. It will also likely shorted the life of the water heater as there is likely heat build up in the combustion chamber rolling out by the gas control valve.

Regardless, an after market inducer is not recommended this type of application. The problem is likely caused where the vent comes out of the house transitioning from a where it's relatively warm (inside the house), to where it's cold outside. This is one of the reasons that your venting setup is not recommended. It also creates an abundance of condensation that causes the flue pipe to prematurely rot out.

If you have a mason chimney in the house for a furnace or boiler, it might be worth while moving the water heater to where it can vent into the chimney. If the chimney is for a wood burning fireplace, then you wouldn't be able to vent it into the same chimney.

In my opinion, the best fix is to replace the water heater with a power vent type. This has an internal induction motor that blows the exhaust out of the house. There are sensors inside of it that will detect heat build up and shut the heater down. The vent only has to go out the side of the house, not up above the roof.

I would be insistent that the plumber remedy this situation. He is the one responsible for the proper operation of the water heater. It's obviously not working (right) the way it is. Sure it's making hot water but is creating a safety issue.

My 2 cents.
There is another option, and that would be an electric water heater. While it may cost a little more to operate, it has these advantages:
1.) Lower up front cost. Electric units cost a lot less than gas power vent types.
2.) Power vent units have higher maintenance costs and are more complicated to repair.
3.) No flue to worry about, replace, maintain or modify.
4.) Zero risk of carbon monoxide.
5.) Electric water heaters seem to last longer.

An electric water heater is also an alternative as mentioned. Just note you will need a 220V electric line for hookup.

Thanks for the input. May just go with an electric water heater to solve the problem.