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benjamincall 01-20-2009 06:58 PM

Boring holes in a load-bearing bottom plate
Hi folks,

I plan to bore a 1-1/4" hole (36 percent of 3-1/2") in a 2x4 bottom plate (bearing, exterior wall) to accommodate 1" Wirsbo Aquapex coming from my well pump in the basement and supplying my tankless water heater in the attic. Will this scenario pose a structural problem? What about a 14.5" length of lumber inserted between the studs to double up the bottom plate. I guess the point of contact between the rim joist and the bottom plate bears most of the load, right?


Ben in North Jersey

Reilley 01-20-2009 07:12 PM

No, this won't pose a structural problem. Taking it out of a load bearing stud may (should stay below 25%) but not the bottom plate.

benjamincall 01-20-2009 07:19 PM


Originally Posted by Reilley (Post 216350)
No, this won't pose a structural problem. Taking it out of a load bearing stud may (should stay below 25%) but not the bottom plate.

Awesome! Thanks for the quick response!:thumbup:

Clutchcargo 01-20-2009 07:28 PM

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Running a water line in exterior wall isn't a good idea, it's prone to freezing.

Reilley 01-20-2009 08:59 PM


Originally Posted by Clutchcargo (Post 216362)
Running a water line in exterior wall isn't a good idea, it's prone to freezing.

True. You'll want to keep the lines on the warm side of your vapour barrier.

Being that he is putting his water heater in the attic, I will assume he is in a warm climate.

benjamincall 01-20-2009 10:05 PM

Tell me about it
I discovered a river springing from the side of my house where somone had run copper on the wrong side of the insulation. Here in New Jersey we had record-setting cold temperatures and very little heat in house (electric space heaters on the main floor). I hope we'll be OK given the diameter of the PEX and the fact that I'm going to put it on the interior side of the insulation. Do you think I need to sleeve the PEX in foam insulation before it hits the attic? I intend to replace the siding, so what about Dow EPS sheathing on the outside? I don't really have many options to route the PEX to the attic. I spoke with Rheem about the installation and they said that the water heater has an anti-freeze mechanism. Of course the manual says you should drain the thing when you expect freezing temperatures. I'm not sure what to believe. Any ideas?

TBFghost 01-20-2009 10:18 PM

NJ is not exactly considered a "warm climate"

Clutchcargo 01-20-2009 10:46 PM

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Is your attic space inside the envelop? If not I wouldn't put the water heater there. Even though the water heater will protect itself from freezing, the pipes and fittings won't.

benjamincall 01-20-2009 10:47 PM

New thread?
Maybe I should start a new thread on the attic tankless installation.

benjamincall 01-20-2009 11:03 PM

I understand "envelope" to mean the portion of the house that is sealed off from the oudoors, i.e., not my vented attic. What would you think about extending the envelope to a small portion of the attic?

benjamincall 01-20-2009 11:16 PM

According to Rheem:


A confined space is one having a volume
of less than 50 cubic feet (1.4 m
3) per
1000 Btuh (0.3 kw) of the aggregate input
of all appliances within that space.

Pretty much any enclosure I build up there will require a huge vent, so I'm not sure what I'd accomplish. Want to trade me your direct vent model?

Termite 01-20-2009 11:17 PM

Good idea. You're asking for all sorts of problems putting a tankless unit and the associated pluming in an unconditioned attic space.

You're ok drilling the hole in the plate. Not a problem. Nailguards will be required at the plate penetrations.

benjamincall 01-20-2009 11:56 PM

What is a reasonable way to modify the attic for my install? I can't conceive of any place I could put it in my basement. What about a small enclosure with a louvered vent to the living area? I could easily tap in to over 10,000 CF of living space that way.

ponch37300 01-21-2009 11:05 AM

I don't know much about the tank less water heater but I have seen pex freeze. Granted it was 1/2" but even 1" will freeze, just take a little longer. I live in Wisconsin and deal with the same freezing temps as you. I would not put anything water related in the attic or on the exterior walls.

Clutchcargo 01-21-2009 12:35 PM

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You have a basement and there's not enough room on any exterior wall to hang it? Wouldn't it be much simpler to drill the vent through the foundation and run water lines from the well?

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