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Community and Q&A

Hose bib/hydrant and thick exterior foam

BWJames | Posted in General Questions on

I’m looking for ideas and insight into a detail I’ve yet to see covered in any of the many many good articles/papers/forum posts here or elsewhere:

Hose bibs/hydrants. As something that requires occasional replacement over the life of the house, what has everybody found to be the best way to address flashing/sealing details when using long frost free hydrants? The objective is to allow relatively easy replacement without impacting the air sealing or water shedding if the valve ever requires complete replacement. (I am aware they are generally rebuildable from the front.)

My current retrofit project: Zone 7 with a wall assembly of 2×4 walls, 3/4″ plywood sheathing, 3″ foam insulation, housewrap, 3/4″ furring strips, and LP smartside topping it off.

My current plan for the 14″+ long frost free hose bib is to run a ~1-1/4″ PVC through the rim joist with a slight slope to exterior, and flash everything to that PVC. I intend to pack around bib with caulk backing rod like a water pump gland packing if anybody is familiar with how that is done. Then finish both ends with a good sealant. 

The hope is that this will allow for relatively easy replacement if it is ever necessary without disturbing the various layers of flashing through the sheathing, foam, WRB and siding.

Is there any better ideas out there on this detail? Thanks!

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  1. Jon_R | | #1

    Make sure that the actual valve seat and enough metal is fully exposed to the interior air/heat. A frost proof hose bib is all about the ratio of internal heat transfer to external cold transfer. Ie, I'd use > 12". Or use an external foam cover or drain it for the Winter. Even better would be some kind of quick release/union that would allow removing the entire hose bib for the Winter (no thermal bridging). Or a yard hydrant.

    1. BWJames | | #4

      Thanks! I currently do all three (long hydrant, water drained, and foam cover.) But I have had the benefit of an extremely leaky house on my side until now.

      The idea of being able to quickly remove it is actually pretty brilliant and easily facilitated with the pipe-within-a-pipe approach.

  2. Expert Member
    Akos | | #2

    I've given up of frost proof shutoff with thick walls. Because the shutoff is near ground level, stack pressure tends to cause cold air to come in around any small gap and the valve freeze in the middle of the wall.

    The no headache is the old style with interior shutoff and drain valve. With pex pipe, even if you forget to drain it, the worst that can happen is a busted exterior shutoff.

    1. BWJames | | #6

      I agree. I've been fortunate in the cases where I've forgotten to drain before an early cold snap. I like to think my belt and suspenders approach of frost free hydrant + shutting off and draining has saved me. I think it may have also been in my favor that all my hydrants are exposed in the interior side thanks to my heated but unfinished basement! In the future I will not be so fortunate! Thanks for the reply.

    2. Jon_R | | #7

      > valve freeze in the middle of the wall.

      But it won't if the valve is well into heated interior space (vs in the middle of the wall).

      1. Expert Member
        Akos | | #8

        I'm in the land of 16"+ foundations. The longest standard ones the box stores carry is 14" which is not enough. You can order longer ones, but the cost of those is way more than the 3 valve setup.

        1. BWJames | | #19

          I didn't find the special order lengths to be particularly egregious, the extended length hydrants weren't that bad I didn't think. ~$35 USD for an in-stock 12" or ~$55 for a special order 24".

          Though to your point, definitely cheaper than going old-school. In my case with a Pex manifold system I don't even need 'extra' valves as they already have a shut-off with drain.

          Coincidentally, that air leakage that has caused your headaches is exactly what I'm looking to solve here. With a foam packing, positive interior seal and a foam gasket between the PVC penetration and the hydrant I'm fairly certain I will have a complete air tight penetration. But I don't think I'll be testing it on some -40F nights.

          1. this_page_left_blank | | #21

            What brand and where did you get the quote from? The only one I was aware of that you could get custom lengths was Aquor, and they quoted me $250 for a 22" stem.

  3. Expert Member
    BILL WICHERS | | #3

    You can get long freeze-proof shutoffs. The valve seat is at the far end from the handle, so the actual valve seat will be (should be) on the inside of the wall. Just make sure you don’t leave anything connected that will prevent that last bit of water from draining out.

    If you are using PEX, a short piece of copper connected to the valve assembly to add some heatsinking prior to the transition to PEX will help keep the valve seat a little warmer.

    Lastly, you might be able to use an electrical fitting — a “cable gland” — in an unusual way to seal your setup. Electrical conduit threads will fit water pipe fittings. A cable gland is a fitting with a large rubber grommet that tightens with a nut. Normally these tighten on a round cable to provide a weatherproof seal, but you might be able to use one on the inside end of your PVC pipe to provide an air seal against the pipe for the spigot. I’ve never tried this, but it MIGHT work. Then you could just put some backer rod in to keep out critters knowing the cable gland would provide the air seal for you.

    I see no reason why your PVC sleeve idea wouldn’t work. The only potential issues I can see are the freezing concerns everyone has mentioned, and it may be tricky to get a good air seal without using something like canned foam. I’d put a ball valve inside as an indoor shutoff for some extra protection, and use one of the ball valves that has the drain port on the side so that you can drain and water from the cold, outdoor side of the valve.

    BTW, make sure you provide a rigid surface on the exterior of the foam for the spigot to mount to. If the mount is wiggly your sealing work will fail when people connect and disconnect hoses.


    1. BWJames | | #5

      That's an interesting idea with the cable gland. Sounds a lot nicer to just undo that fitting vs. digging out sealant in 20 years when the valve is crudded up beyond repair.

      Unfortunately, my current hydrants are not cylindrical. The threaded side where the valve lives is much larger in diameter and has a larger than the diameter hex on it. So no good there. But I have seen PEX specific hydrants that appear to be cylindrical all the way down where some sort of rubber seal would be a great solution.

      In addition to air sealing extremely well, in the unlikely event of a burst hydrant (being a far-norther, draining hydrant lines is part of the gig), it could actually direct all the water out of the house if that exterior seal/gasket was the weaker of the two links. At least until the water in the PVC froze and burst... It's worth further consideration. Thanks a bunch for the ideas.

    2. BWJames | | #15

      After some additional consideration, I realized Fernco has a line of wall sleeve seals that would be absolutely perfect sealing the interior side of this penetration very much along the lines of your cable gland concept.

      However, they don't make them quite small enough! Pretty disappointed. But I will definitely keep these in mind for some larger penetrations - particularly one subgrade for my well.

      Image courtesy of

      1. Expert Member
        BILL WICHERS | | #16

        If you need it to seal on a smaller pipe than it’s designed for, wrap some splice tape on the pipe at the seal area to build it up. “Splice tape” is a thin (maybe 1/32” thick) stretchy rubber tape without adhesive. Electrical supply places will have the stuff and probably box stores too. Use that rubber tape to build up the pipe diameter, than put a few wraps of scotch 88 black electrical tape over that to hold the splice tape in place. This method will make a long-lasting “gasket”.

        You can also build the pipe diameter up with the 88 tape alone, but since the 88 tape is thinner, you’ll need a lot more wraps so it will take you longer.

        Do NOT use the cheap electrical tape for this. The cheap stuff will squish around into a sticky mess in a short period of time. There is a reason why the cheap electrical tape is around 50 cents a roll and the good stuff is closer to $3. You absolutely get you’re moneys worth here.


        1. BWJames | | #18

          I think if I was going to resort to something involving tape just to make the coupler work - I'll just use Zip Stretch or some similar flexible flashing product and call it good. Though i'm sure your suggestion would work.

  4. AJ__ | | #9

    Roflex gaskets from 475 Building Supply are another option

    1. BWJames | | #12

      Thanks Alex, those look intriguing. Any experience with their flexibility long term?

      1. AJ__ | | #17

        No direct experience as yet, but they are made of epdm which is known to retain its flexibility for a long time. I've seen a few frost free hose bibs with issues and so for my own house I'm looking at using the Roflex gaskets because it would allow for easier replacement of the hose bib should there be any issue vs a flashing system which adheres to the hose bib.
        See Eric's posts on them here

  5. user-7022518 | | #10

    I'm not sure if the sizing works for your exterior insulation but this is the product we decided to use: I am making my own gaskets out of scrap EPDM and tape. Lisa

    1. BWJames | | #14

      That is a pretty interesting product. Honestly a little too non-standard for me and it doesn't look quite like something that would be a good fit for my application. But I appreciate the concept.

      Thanks for sharing.

  6. Expert Member
    Peter Engle | | #11

    There's been good discussion here about the risks of freezing and such, but little about the general approach itself.

    I like it for many (most) exterior penetrations. I've done this with one of the biggest national production builders and it works great for scheduling all of the subs. If you pre-position PVC sleeves through the wall at all known penetrations (you always miss a few) for plumbing electrical, HVAC connections, etc., you can do all of your framing and weatherproofing without worrying about the subs poking holes in your wall systems. They just come in at the end, cut the PVC to length, install their utilities through the sleeves and seal them.

    About the only key to this approach is to flash the sleeve at the level of your WRB. We used QuickFlash with this particular builder. Nearly idiot proof.

    1. BWJames | | #13

      Thank you Peter, you nailed it. My question was poorly worded and did not make clear I was looking specifically for input on the flashing details to prevent disrupting the wall systems integrity.

      Ultimately, sounds like I'm on the right track with the PVC.


      1. potton | | #20

        Bradley, How did you proceed finaly ...?

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