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No draft in hot water heater's vent connector

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Hello, I recently had a full home heating assessment by MassSaves. Over the 4 hour assessment & all the tests, there are only 2 things I need to take care of in order to get all the financial assistance from MassSaves for insulation etc. One thing I need to take care of is: The rep from MassSaves did a test where he took a device that looked like a pen light & he held it to the pipe above my hot water heater (which is fairly new & fine), he turned on this device & a small stream of Co2 (or the like) came out. He said this pipe is supposed to suck this Co2 up, and it didn't. We have brand new Co2 detectors throughout the house. I called my plumber & he said this isn't his area. Who should I call? I am hoping the pipe just needs a cleaning & nothing major. Thank you & I look forward to hearing from you!
asked in Gas Water Heater by althea72 (120 points)
edited by darekrudy
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1 Answer

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Hi Althea72,

It’s a complicated process (the chimney draft) and since I know nothing about the design of your home I cannot give you any definite answers.
Proper draft depends on many conditions inside and outside of your home; chimney type (material), its dimensions, height above the roof, positioning (inside the house or outside), number and type of appliances using the same chimney, tightness of your doors and windows, additional vents and chimneys inside your home (fireplace, exhaust fans, etc.), weather conditions / temperature / barometric pressure at the time of testing, altitude, and a bunch of other things.
A heating assessment company should check all of the above, input it into their software (or whatever they’re using) and based on that information produce some answers. By analyzing it they should be able to tell if the behavior of your chimney is normal or not.
In some cases a water heater chimney will have no draft at all until it is stimulated somehow, by a water heater’s burner for example. As soon as the air temperature inside the vent connector and the flue starts rising, created differential between inside and outside / ambient temperature helps to pull exhaust gasses outside… that’s extremely simplified version of it. 
None or poor draft may happen in an extremely air tight home where there is a problem with balancing fresh air intake (from exterior), or in a home where there are too many constantly active exhausts that create negative pressure and downdraft inside the chimney. 
Since you have to start somewhere you may want to call a local chimney sweep, maybe there’s something obstructing the flue but your CO alarm would most likely alert you about it.
Let me know if you have more questions and when you find out what’s causing the draft problem (if it is a problem).
answered by darekrudy (21,730 points)