Bathroom exhaust fan: condensation/leak?


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Old 10-01-16, 05:02 AM
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Bathroom exhaust fan: condensation/leak?

My bathroom exhaust fan located in the ceiling above the shower seems to leak/condensate. It's approximately 12 years old and seems to work fine. I took pics of both the fan where you can see the black water stains. I also took a pic of the duct which as you can see is vented horizontally. Thoughts? Could this be the fan itself?





 
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Old 10-01-16, 05:15 AM
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First, remove the cover, turn it on and make sure the damper is openinig. That is a long run for this type of fan, but the air should move. Where is it vented to? Is there an obstruction at the exhaust end of the hose? With it all put together, turn it on and hold one square of toilet paper to the fan. It should easily suck it up and hold it.
 
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Old 10-01-16, 05:23 AM
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It actually leads to a vent just under the eaves/soffit on right.
 
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Old 10-01-16, 05:40 AM
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Does the vent under the soffit have a screen or guard to prevent birds from entering? If not it's possible you a nest clogging the duct. How long do you run the fan after each shower?

The exhaust duct takes a rather circuitous route to the soffit. It looks like you have five 90 degree bends and some other misc. turns. Even if it's not blocked by a birds nest you have significant resistance just from the duct length and bends. It also does not help that it's flex duct. The rough interior adds even more resistance to flow.

I have a exhaust fan inside a shower/steam shower. It is a rather small fan but has a short exhaust duct with few bends and it does not drip. I'm certain there is a lot of condensation in the duct especially in winter but there is sufficient airflow to evaporate what does condense so it's not a problem. The fan is on a timer switch which makes it easy to run the fan for 15-20 minutes after a shower/steam. Not only does this get the humidity out of the shower it also allows time to get the ducting dried out.
 
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Old 10-01-16, 06:02 AM
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There is a screen on the exterior vent. We run the fan just while using the shower. I guess I should be running it longer for the evaporation? Would a better fan help as well?

*update - I actually did the toilet paper test and the fan is working fine.

I'm wondering if it makes sense to install new duct (rigid) at least partially?
 
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Old 10-01-16, 06:14 AM
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Rigid pipe makes very good sense due to the convoluted directions your pipe takes. Yes, a more powerful fan could probably make a big difference. Normally the box stores have a display set up where you can see and hear each fan they promote. The larger CFM and lower sones fans are a little more expensive, but well worth it, IMO.
 
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Old 10-01-16, 06:34 AM
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What would be the ideal "rigid" pipe for this? Flex?
 
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Old 10-01-16, 06:46 AM
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The condensation could also be coming from the fan's cold metal box. That fan should be completely buried in insulation so that it stays warm. Attics in your area should have something like R-49, and all I see is a little r-19, with nothing covering the top of the box or any of the duct.

I agree the duct is convoluted and that rigid may help (especially if it went straight out (under insulation and under the pvc pipe before rising up over the joists)... but I also think there is a good chance this could be solved with more insulation.... blowing 16" of cellulose in the entire attic would be a good idea imo.

If the condensation was running back down the duct, it would likely be dripping from the flapper corner of the fan only.
 
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Old 01-25-17, 05:37 AM
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Hi all,
I'm having a related issue. Yesterday (Tuesday) I noticed a water stain on my upstairs bathroom ceiling. In the attic we saw that the duct/pipe connected to the bathroom fan was dripping at one of the joints along the pipe that was sealed. It was a rainy day, in case that matters. However, the only spot that seemed wet on the pipe was in the area where two pieces of straight horizontal pipe connected. This bathroom isn't one we use often. However, we had some work done in our other shower so my husband and I both used the shower on Sunday. Since we don't use this bathroom often I don't know if the water stain happened sometime after the showers on Sunday, but either way on Tuesday when we discovered this the pipe in the attic was still wet.

Any thoughts on the problem and the solution?

Thank you!
 
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Old 01-25-17, 06:34 AM
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Rabtaido,

Joints in your ducts should be taped with a foil tape and the entire duct should be buried deep in your insulation to help keep the pipe warm.
 
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Old 01-25-17, 07:13 AM
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Hi XSleeper,
Thanks for your response. I have a new home that is only 6 months old and in the attic i can see this pipe run horizontally across the attic above the insulation. Is this something new constructions should have had done? Especially in New England? It does have the foil tape along the leaking joint, but not insulation.
 
 

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