what takes it so long

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by DIY, Jan 8, 2009.

  1. DIY

    DIY New Member

    Messages:
    153
    Location:
    Florida
    My house was totally re piped @ 4 months ago,and with that re pipe i decided to get a new water heater to (whirlpool "low boy" 30 gal capacity) no bells and whistles just your basic electric HWH. CPVC was used for the hot and cold sides inside the house tub/shower,bathroom sink,toilet and kitchen sink. The HWH is located in the kitchen and the hot and cold lines coming from it run along the kitchen wall under a counter top,and proceed out an exterior wall where @ 15' of pipe hot and cold runs underground and @ two 3' portions run along the outside of an exterior wall. All hot and cold lines either exposed or underground are foam stick insulated. Now the question. It takes a good 30+ seconds to get hot water when the tub or any sink faucet is turned on. Should i change the underground hot line portion to copper?,re trench the hot line and cover it with more insulation? turn up the thermostat on HWH... Advice,suggestions and remedys welcome.Thanks all!
  2. leejosepho

    leejosepho DIY scratch-pad engineer

    That is an issue of flow rate and how much cold water has to be pushed out ahead of the hot water being sent into the line ...

    Those kinds of things can affect the temperature of the supplied hot water coming out of a faucett, but they will not change how long it takes for the hot water to actually arrive.

    There are various types of recirculation lines that can make fully-heated water available almost instantly whenever a faucett is opened, and you might want to consider one of them. The simplest is a small pump under the farthest sink, and the cold line can be used as a return if you do not want to add a dedicated return line.
  3. DIY

    DIY New Member

    Messages:
    153
    Location:
    Florida
    Thank you for the reply Leejosepho. I have wonderful water flow.Infact flow was one complaint i had before the re pipe. If flow seems to be the problem then what caused a re pipe to obstruct flow? Or are you saying to much flow now?... I'd like to learn more about this resurculation dedicated line or tank and how it works..? Thanks
  4. DIY

    DIY New Member

    Messages:
    153
    Location:
    Florida
    what takes so long

    correction: recirculation
  5. 30 gallon electric water heater only provides 18 gallons of ready to use hot water.
  6. jastori

    jastori New Member

    Messages:
    118
    Location:
    Illinois
    Is it possible that your new lines have a larger diameter than the old lines?

    This is generally a good thing (will improve flow). The downside is that it will take longer for the hot water to reach your fixtures.

    If a faucet supplies 2 GPM (gallons per minute), and it takes 30 seconds for the hot to reach the faucet, then the pipes are holding 1 gallon of water.

    If you upgraded your supply lines from 1/2" pipe to 3/4" pipe, for example, you would roughly double the volume of water stored in the pipes, and therefore double the amount of time that it takes the hot water to reach the faucet.
  7. leejosepho

    leejosepho DIY scratch-pad engineer

    Yes, that is what has happened.
  8. leejosepho

    leejosepho DIY scratch-pad engineer

    Do a search for "recirculation" right here on Terry's boards and begin reading!
  9. DIY

    DIY New Member

    Messages:
    153
    Location:
    Florida
    Good point Jastori. Most of the re pipe is upgraded to 3/4" CPVC inside and T's off to the shut off valve in 1/2" pipe. That answers some other questions to... Anyway,with that now known,is a recirculation line and/or pump the only way to fix this wasting water till hot water is available? Thank you
  10. Nate R

    Nate R New Member

    Messages:
    472
    Location:
    Milwaukee, WI
    Please explain. Is this because the remaining 12 gallons are diluted with incoming cold water? Is it different for a 30 gal gas heater?

    What about a 40 gal tank?

    I ask this because: We have a 30 gal gas heater now. We have installed a deep tub. (32 X 60 X 20) I'd guess the hot water is at about 130-140 degrees, and we don't get the tub full up to the overflow with a person in it before running out of hot water. It's close enough that I'm hoping upgrading to a 40 gal will be enough to get the tub filled. (Don't really have room anywhere for larger than a 40 gal)
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    A big tub could hold 80 gallons or more (the spec sheet for your tub would say how much it holds). Now, depending on the WH thermostat setting, you normally don't use only hot, you mix it with some cold. The hotter the WH is, when mixed with cold, the more 'warm' water you can get to fill the tub. But, because you are replacing the hot water in the tank with cold, even though hot rises and you are inserting the cold at the bottom, you'll never be able to empty the WH and expect it all to be hot. Thus, depending on the design, you may only get 70-80% of the volume of the tank as hot before the incoming water cools it off, especially at a tub filler which can flow possibly 5-15gpm, depending on the size of the supply pipes and the valve used. Think how long it takes to heat a pot of water on your stove, then think about 5-15 gallons/minute and you can see you either need a LOT of heat, or a bigger tank. If you look at the spec sheet for the WH, it will tell you how much hot water you can get out of it. Some WH have higher power heaters to help extend the hot supply, but they cost more.
  12. DIY

    DIY New Member

    Messages:
    153
    Location:
    Florida
    In ways this does not make total sense to me yet,but just thinking aloud here.Would replacing any of the 3/4" hot side CPVC pipe with 1/2" CPVC be advantageous to getting hot water faster at any of the fixtures.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    That might cause the pressure balance valve to lock up...
  14. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    There is a " 70%" rule which applies to water heaters, gas or electric. In short term analysis...i.e. during a shower......you can get 70% of the gallon capacity of the WH, still at a temp within 20º of set point. Yes , this is due to mixing of cold in as soon as you start to draw. For a 30 gallon tank, this gives a figure of 21 gallons. Obviously, set point and groundwater temp affect this, but the 70% rule is a good starting point.

  15. Any water heater, no matter electric or gas that is a tank type heater, the amount of water it takes before there's "significant" temperature drop is 12 gallons of water.


    So, a 50 gallon heater would be 38, 40 gallon would be 28, 30 being 18.

    Cold water displaces the hot to get the hot to leave the tank...at some point it will start tempering the water's temperature in doing so.
  16. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    Rugged what about the 25 gallon heater Bradford White makes that gives 155 gallons of hot water for the first hour? Granted iits thermostat is set to 180, and they use a tempering valve to temper the water to 120 as it leaves. Also it rated at 85,000 btu's.


  17. That's a huge difference, like apples to grapes. Why isn't this a popular model being sold in residential, given that potential? Expensive to operate?


    I'm just mentioning normal residential applications with tank settings of 120 degrees, average incoming water temperature of 50-60 degrees.
  18. leejosepho

    leejosepho DIY scratch-pad engineer

    Smaller pipes certainly do hold less water, but there would still be a wait for hot water at the end of the line. Do a web search for circulator pumps and look for ones used in bathrooms.

    The one I use has a button on the wall to push when you want hot water, and it only takes about 5 seconds for the pump to get the water there and shut itself off. Some people use timers to have hot water immediately available at shower time, and there are proximity sensors that can start the pump whenever someone walks into the bathroom or wherever.

    The simplest plumbing is to have the pump circulate into the cold line, and that is what I would suggest. The pump's aquastat will shut it off just as soon as the hot water arrives, and than means your cold line will not be filled with hot water. The only reason I have a dedicated return line is because I also use my circulator pump to feed a small heater under the sink.

    Here is a picture of the pump I have, and you can presently find several for about $60.00 each on my favorite auction site ...

    Attached Files:

    Last edited: Jan 9, 2009
  19. Ladiesman271

    Ladiesman271 Homeowner

    Messages:
    221


    Would a residential application of a standard water heater be better off with a higher tank setting and the addition of a tempering valve, or is that just a waste of time?

    By the way, my incoming water temperature is now 40 degrees after the pipes are clear of room temperature water. No problem maintaining unlimited volume of 120 degree temperature water with my old Aquastar tankless.

    One other note. 120 degree water is not high enough a temperature if you have a cast iron tub. That cold cast iron sucks a lot of heat out of the hot water!
  20. Ladiesman271

    Ladiesman271 Homeowner

    Messages:
    221

    I have 1/2" hot and 3/4" cold copper water pipes. The longest run is about 70 feet of pipe, and it takes about 30 seconds for the water to get fairly warm. I insulated the hot water pipes to get the hottest water possible to the water outlet point.

    Just wondering, do you have some type of water shortage? The cost of water is a lot cheaper than the cost of the fuel used to heat it. Heck I turn on the shower, and by the time I get in the water is plenty hot. Big deal, so I "waste" a gallon of water.

    Do you time the length of your showers also? That will save you more water and energy than fiddling with plumbing.
    Last edited: Jan 9, 2009
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