My roofing contractor and I are trying to figure out the appropriate sealant to use between the storm collar and type-b vent pipe and the flashing and type-b vent. Selkirk recommends silicone, duravent and American recommend hi temp silicone. The previously installed sealant (NP1 - 180degF max service temp) is leaking water during normal rain on two 3" hot water heater vents and one of two 4" gas furnace vents. Hi-temp silicone comes in products that are used as fire barriers up to 1800 degF down to silicone sealants with service temps to 400 degF. Can you suggest a couple products you have used that seal good and keep water out?
Gas Flue Vent Sealant
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JamesDT
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My roofing contractor and I are trying to figure out the appropriate sealant to use between the storm collar and type-b vent pipe and the flashing and type-b vent. Selkirk recommends silicone, duravent and American recommend hi temp silicone. The previously installed sealant (NP1 - 180degF max service temp) is leaking water during normal rain on two 3" hot water heater vents and one of two 4" gas furnace vents. Hi-temp silicone comes in products that are used as fire barriers up to 1800 degF down to silicone sealants with service temps to 400 degF. Can you suggest a couple products you have used that seal good and keep water out?
No. But b-vent pipe design/code requires that it withstand 400 degF. 3 of the 4 vents have failed between 2 months and 12 months of installation and are leaking water. Manufacturers of type-b vent pipe require hi-temp silicone, but there are many different types. Which ones have you used with success. Wish i could figure out how to post pics of leaks...
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Most cheap clear silicone is rated for 600°f+ if you look up the product information sheet. That's what I use.
Yes. My roofing contractor is doing the roof work because the hvac contractors wont get on a 10/12 roof - neither will I. He has come over previously with low temp stuff that he thought was acceptable. Im looking for professional advice so he can complete his work.
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If you are really worried about it the high temp red stuff from the auto parts store is definitely rated high enough but it's really ugly and the clear GE stuff from Ace hardware is only rated a few degrees lower which is still well above 400°f
I cant find clear silicone that is rated to 600 degF. This is what I get when I simply google hi temp silicone.
3M Fire Barrier 1000degF
Rutland High Heat Silicone Sealant 500degF
Vitcas® Heat Resistant Silicone 1800degF
Rectorseal Hi-Temp Red Silicone Sealant 650degF
Dap HVAC Silicone 100% RTV Silicone 475degF
Meeco's Red Devil Silicone Hi-Temp Sealant Red 550degF
I dont have any experience with these regarding sealing storm caps on gas flue vents. However, the material seems to be heat resistant. So I'm looking for actual experience in recommending several sealants that actually work in this specific application.
3M Fire Barrier 1000degF
Rutland High Heat Silicone Sealant 500degF
Vitcas® Heat Resistant Silicone 1800degF
Rectorseal Hi-Temp Red Silicone Sealant 650degF
Dap HVAC Silicone 100% RTV Silicone 475degF
Meeco's Red Devil Silicone Hi-Temp Sealant Red 550degF
I dont have any experience with these regarding sealing storm caps on gas flue vents. However, the material seems to be heat resistant. So I'm looking for actual experience in recommending several sealants that actually work in this specific application.
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600° is excessive and unnecessary.I cant find clear silicone that is rated to 600 degF. This is what I get when I simply google hi temp silicone.
3M Fire Barrier 1000degF
Rutland High Heat Silicone Sealant 500degF
VitcasHeat Resistant Silicone 1800degF
Rectorseal Hi-Temp Red Silicone Sealant 650degF
Dap HVAC Silicone 100% RTV Silicone 475degF
Meeco's Red Devil Silicone Hi-Temp Sealant Red 550degF
I dont have any experience with these regarding sealing storm caps on gas flue vents. However, the material seems to be heat resistant. So I'm looking for actual experience in recommending several sealants that actually work in this specific application.
Heat Resistant Silicone 1800degFI've been using the GE clear silicone for years and others have been using it much longer than I have on applications they get hotter than class B vent is allowed to.
R600 - ok so 400degF service temp clear silicone should work at least GE Silicone from Ace. I'm not concerned with the super high temp stuff. I'm just trying to get advice on what stuff is acceptable. In fact the 1000+ degF stuff looked like it might not be flexible enough to give a good water seal. This is why we wanted to ask the experts...
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Yes that is the exact stuff that I've been using for years.
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Well I would have agreed with him in the past unfortunately anything that can handle the temperatures isn't going to be very durable. GE silicone is just fine as long as there is absolutely no stress, it cannot handle movement because it has very little strength and that's the case with all silicone products.
I have also used through the roof sealant and it works wonderful but it is definitely not rated for the temperatures.
That's why the storm collar needs to be just slightly above the flashing so that it won't touch and it needs to be sealed to the pipe only that way the sealant won't be stressed unless somebody climbs up on the roof and messes with it.
From my standpoint, I'm just going to say the expert advice is pointing towards clear silicone with a service temp of 400 degF. Also, that he should consider just sealing the storm collar to the vent pipe and not sealing the flashing to the vent pipe. From his standpoint he will be warranting the work will not leak (12 mos), so he will have the final say. However, I will let him know the 400 degF silicone is a manfacturer requirement and is an industry best practice and that this shall be followed. Please let me know if you think this is unreasonable.
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That sounds perfect to me.
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