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Thread: pipe insulation for cold water

  1. #1
    DIY Junior Member bikeythekid's Avatar
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    Default pipe insulation for cold water

    Hello-
    I have uninsulated cold and hot water pipes running together with heating pex close by for a 60 foot chase. As a result water in the morning is warm for about 4 minutes and the refresh rate on warming it up again is around 6 hours. Regardless, there is no real chill to the water as you get to the top floors (very cool but not ground water cold at all, I don't even know if that is a problem for people.) This building is still a construction site with very little to no demand for water. The building with soon house six people. People I have spoken to have tried to assure me that with a family of six and the accompanying water usage, the water won't have time to warm on the main cold line except overnight, so my only issue would be the branch lines, which only hold 10-30 secs of water max. I should add that the person assuring me this would not be a problem was the person who forgot to insulate the pipes.
    First question is: Does this guy have a point in regards the warming not being an issue when a family moves in starts using 80-100 gallons a day per person (average consumption is my city so 5-600 gallons a day)?
    Secondly, it is worth cutting open areas to insulate as much as I can? If I can get to 75% of the pipes would that make a noticable difference or would the pipe I couldn't get to cause a thermal bridge into the insulated stuff?
    Lastly, what insulation would you recommend?

    Thank you, Bikey

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    I think the answer might depend on how warm the water is.
    Most people have little need for water that is truly cold.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    As an aside, there's an advantage of the pipes getting warm, you should never have one freeze up on a long-cold spell!

    Circulating it won't help unless there's a long section where you could drain off the heat like a radiator. It's not like you've got a reservoir of cold water sitting anywhere you can replace that hot water with.

    Insulation might help some, but that could open you up to freezing lines. Tough situation. Relocation of the piping would likely be expensive as could cutting walls and trying to insulate.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member dlarrivee's Avatar
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    Is the hot a recirc system already?

    It will naturally cool off and wont be heating the cold side up any longer...

    Insulating the pipe doesn't make any sense, installing the pipe so close together doesn't make any sense.

  5. #5
    DIYer, not in the trades LLigetfa's Avatar
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    Unless you plan to drink water straight from the tap first thing in the morning, I don't see a downside to it being tepid.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    It would keep the shower temp changing until the lines were purged...you might consider a thermostatically controlled shower valve - set it and forget it to keep your desired temp. That type of valve will continue to adjust the cold, up or down, to try to maintain the setpoint.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member dlarrivee's Avatar
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    I would consider installing the piping properly instead.

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    DIY Junior Member bikeythekid's Avatar
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    Quote Originally Posted by dlarrivee View Post
    I would consider installing the piping properly instead.
    Thanks for the actionable advice. Now if I could only find my time machine......

  9. #9
    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by bikeythekid View Post
    This building is still a construction site with very little to no demand for water. The building with soon house six people.
    Sounds like time is of the essence. You usually only have one chance to do something correctly, it seems you have as second chance here.

  10. #10
    DIY Junior Member bikeythekid's Avatar
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    Quote Originally Posted by dlarrivee View Post
    Sounds like time is of the essence. You usually only have one chance to do something correctly, it seems you have as second chance here.
    I wish I knew how. I'm one of the six people trying to move in. The contractor just wants to shoot in cellulose insulation into the walls but I don't think that will do anything and then we would have made accessing the pipes that much more difficult.

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    Dense packed cellulose is probably better insulation than the foam you could install especially because it would block any air movement around the pipes. But, depending on where the pipes are run relative to the outside wall, adding insulation might let them actually freeze, depending on where they are relative to the outside wall.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    DIY Senior Member Runs with bison's Avatar
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    Can't say if the rework is worth it, but I generally like to keep the hot side hot, and the cool side cool when it comes to my home's plumbing (and HVAC ducts.) Seems rather wasteful to have the hot water line heating the cold water line since over half of that cold water will be used for toilet flushing and other non-hot water uses.

    In our home we have uninsulated supply & return ducts side-by-side which is rather stupid. There is also a water line running to the kitchen past the ducts, so the water temp in the ~45 secs it takes to get hot water is warm in heating season and cold in cooling season.

    I like to be able to pull cool water right from the tap into a glass. We don't use refrigerator water dispensers since I always considered them a waste of space in the fridge. We use ice of course, but I prefer the tap.

    Our home water use is 33 gal/day per person, substantially below the U.S. norm, but we use very low flow shower heads, HET toilets, an Energy star dishwasher, and a front loading clothes washer.

    Good luck!

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