Why does the water take so long to warm up?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by dpd, Dec 16, 2010.

  1. dpd

    dpd New Member

    Dec 16, 2010
    My wife and I just bought our first house a few months back so I'm pretty new at all this. Sorry if this is a stupid question.

    Here's the problem. The water in the house takes what seems like a really long time to get from cold to hot. Especially in the bathroom that is farthest from the hot water heater. Also, once the water does warm up and is then turned off it is cold again in minutes and you have to wait for it to warm back up.

    My question is, is this normal? Just something we'll have to deal with? Or is there something else going on?

    Thanks so much!
  2. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima WA
    It's normal. When the water sit in the line, it loses heat. All of that cool water has to be purged from the line by the incoming hot water. The larger the pipe and the longer the distance, the more cool water there is to be flushed out, and if you have 3/4" pipes, there is almost twice as much water as there would be in a 1/2" pipe. There are a couple of ways to deal with this. If there is access to put a return line from the most distant fixture to the water heater, a recirculating system works very well. You have virtual instant hot water as long as the pump in the system is operating. Some pumps are on a timer, some are not. There are other devices that do not require the return pipe that work pretty well also. I am most familiar with the system with a return line. I do not have a timer so the pump runs 24/7. It has been in place for about 8 years and shows no sign of wearing out. Of course it will someday, but replacing the pump will be a 5 minute job (after I get the pump)
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    When you turn on the faucet you have to flush all the "cooled" water out of the pipe and the further the faucet is from the water heater the longer it takes to do this. The hot water also has to heat the pipes along the way so it loses as little temperature to the environment as possible on its way to the faucet. When you turn the hot water off, the water starts to lose its temperature, through the pipe walls, to its environment. The speed that this happens depends on several factors, some of which are; is the pipe insulated (probably not), what is the temperature where the pipe is located (probably cold), the length of the pipe, etc. Plumbers could install a "retrofit" circulation line which would provide hot water sooner, but which has some "side effects", namely, sometimes will get some initial warm water from the cold faucet, the heater will operate more frequently, your gas or electric bill will increase slightly and your water bill will go down a bit.
  5. Thatguy

    Thatguy Homeowner

    Aug 27, 2008
    A bounty hunter like in "Raising Arizona"
    100' of 1/2" ID pipe should give you hot water in 30 seconds at your sink aerator's flow rate of 2 GPM. For a 6 GPM bathtub, 10 seconds.
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