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Insulating in/out pipes from Nat Gas HW tank

Posted by alan_s_thefirst (My Page) on
Wed, Oct 20, 10 at 2:01

It seems to be a bit of a conundrum, we are supposed to insulate the in/out lines from our hot water tanks (many new tanks are supplied with foam insulating sleeves) yet we're supposed to keep combustibles 6" or more away from the flue...and of course the open part of the flue hat.

The water lines on my tank are particularly close to the flue hat, in fact the edges of the plastic disks that cover the inlet/outlet that face the flue have actually melted a little. I checked the exhaust gas flow with a candle and it draws up the b-vent correctly.

I had considered using the fibreglass pipe wrap covered with foil duct tape at least along the adjacent part to the b-vent/flue, and the foam sleeving further up.

I know the plastic foam is probably flame-retardant but I'm sure they'd melt that close to the flue.

Am I over-thinking it?


Follow-Up Postings:

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RE: Insulating in/out pipes from Nat Gas HW tank

As long as you have proper ventilation in the room where the tank is located the sleeves provided are not a problem.


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RE: Insulating in/out pipes ftank

The water lines in and out must not be closer than straight up.


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RE: Insulating in/out pipes from Nat Gas HW tank

Thanks - the lines don't come any closer, and they're flexible plastic or whatever, sleeved with braided stainless. I am just concerned if the plastic covers on the inlets get hot enough to melt/shrink back, the insulation will suffer a similar fate.

Ventilation-wise, there's no 'make-up' air vent from outside ('80's house, British Columbia) which wasn't required then (less stringent air sealing) there is of course the fresh air inlet that connects to the cold air return.

The mechanical room doors are louvred so there's plenty of air flow into the room when they're closed.


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RE: Insulating in/out pipes from Nat Gas HW tank

6" clearance from combustables still applies. Don't put the insulation closer than 6" from the single wall pipe, or 1" from double wall pipe. Leave the pipes uninsulated if you cannot make these clearances.


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RE: Insulating in/out pipes from Nat Gas HW tank

Thanks - makes sense. I'll use the fibreglass wrap up to the 6" point.


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