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Thread: value in insulating hot water pipes

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    DIY Junior Member dmetz's Avatar
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    Default value in insulating hot water pipes

    Wondered if there is any value in insulating copper hot water lines? Seems that it takes longer for the sink water to get hot with copper after replacing old galvanized lines. Any thoughts would be appreciated. - Don

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Sure. In many places, it is now code as I understand it.

    Copper is a better conductor than steel, and it probably has much more static volume, which is one reason you changed things out. While the old pipes and the new may have had the same volume when new, the old galvanized pipes only had a small inside diameter after many years, so the system didn't have to fill it up with hot water.

    In between uses, the hot water in the pipes will cool off - it did it with the old ones too. But, there is more of it now, so it takes longer for it to be purged with hot from the heater before it gets to you. If you have long intervals between hot water uses, the insulation won't help much. But, in between, if it is insulated, it won't cool off as fast.
    Jim DeBruycker
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    In the Trades Gary Swart's Avatar
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    Foam insulation is quite cheap and easy to install. I'd recommend putting it on hot and cold lines. Unfortunately, the only ways you can get hot water faster at fixtures that are some distance away is to either install a point-of-use heater at the point of use or a recirculation pump in the system. Insulation will slow the heat loss, but not prevent it and once the water has cooled, it has to be purged before the incoming water will be hot.

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    Master Plumber Dunbar Plumbing's Avatar
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    Armaflex is denser than cellfoam and they make a webbed wrap that you dip in water and install over the insulation that provides optimum R value.
    Read what the end of this sentence means.

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    DIY Junior Member dmetz's Avatar
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    Thanks, I appreciate the info. If we put in the insulation I will time the difference in temperature rise at the faucet. Just curious how much of an effect the insulation will make. I have a digital thermometer that would cover the entire range of the temperatures. - Don

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Once the water is cold...having insulation on the pipe will have a very minimal difference. It will be determined by the volume you have to flush out. It will make a (very) minor difference in radiated losses, but may not be much.

    The thing of interest would be the ultimate temperature that arrives. With insulation, it should get a little hotter, since it won't cool off as much. Depending on where the pipes run, and if you can get to the entire run, it could be a lot if the pipe runs in a very cold area.
    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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    In the Trades brownizs's Avatar
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    dmetz, It is actually better to insulate, then not to. After I insulated my hot water pipes, it took less time to get hot water to the faucets, and found that the water heater does not fire up as much with that also, due to I am not pulling as much water through the pipes to get hot water to the faucet.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If you ran the water a little while ago, what's left in the pipe will still be warm. Then, you wouldn't have to run much water to get it warmer. Otherwise, as long as you have a fixture to help minimize convection, the pipes above the heater shouldn't be leaking too much heat, and it won't make much difference about running - it is the volume you have to run to purge the lines of cold water that would cause the thing to run. But, as was mentioned previously, insulating the pipes is code for new construction, and it can't hurt. If you do the cold water lines too, you prevent hot moist air in the summer from making contact, condensing, and dripping on things.
    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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    In the Trades kordts's Avatar
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    as Rugged sez, the armaflex is best. The foam stuff has minimal "R" value.

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    Plumber Cass's Avatar
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    I will bet the reason it takes longer is because the old pipe had a smaller ID due to corrosion so it didn't have to displace as much water as it does now. The corrosion may have acted as some what of an insulator slowing down the heat loss also.

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    DIY Junior Member dmetz's Avatar
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    Great information. The old galvanized was 1/2" throughout, with the new copper I ran 3/4" mains to bath, kithchen and utility then necked down to 1/2" so that is a factor also. Had to clean out a lot of rust particles from the faucets including the pressure balance tub/shower faucet. If we do the insulation and I can come up with some measurements I will share the info.- Don

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