Hot water takes too long; considering three options...

Discussion in 'Water Heater Forum, Tanks' started by chrispitude, Feb 2, 2013.

  1. chrispitude

    chrispitude New Member

    Messages:
    3
    Location:
    Allentown, PA
    Hi everyone,

    Yes, yet another "hot water takes too long" question... We used to live in a small split-level house with the hot water heater directly under the kitchen, and half a floor away from both bathrooms. Hot water was took a couple seconds in the kitchen, and a couple seconds longer in the bathrooms.

    A couple years ago, we built a 2-story house. I wanted to minimize the hot water delay to each fixture, so I went with a PEX manifold setup with dedicated 1/2" runs to each fixture. I hoped the smaller inner diameter would mean shorter wait times. Unfortunately, it still takes an irritatingly long time everywhere. The kitchen is the biggest PITA (and the most noticed by my wife), so that's what I'd like to fix.

    There's about 35' of 1/2" PEX between the hot water heater and the sink, all of it accessible along the unfinished basement ceiling. There is a power outlet in the base cabinet under the sink. The options I'm considering are:

    1. Insinkerator (or other) instant hot-water dispenser in the base cabinet under the sink

    My wife wants me to install an Insinkerator (or other) instant hot-water dispenser. I'm not a fan of that. Sure, near-boiling hot water is nice if you want a quick cup of tea, but it's too hot for washing hands or dishes. In my mind, this doesn't really solve the delay for the common uses. Plus, I read about these units leaking, and I'm not really looking to deal with leaks ruining the base cabinet. Oh yeah, we have a 2-year-old too, who will be able to reach the sink some day.

    2. Small point-of-use hot water heater mounted just under the kitchen floor

    Another option I'd considered is a small point-of-use water heater installed in the basement, mounted right underneath the kitchen floor. I could use Unistrut to make a nice sturdy ceiling mount for it. It would only have to supply enough water to keep the water hot until the water from the main heater mixed into the small tank sufficiently.

    3. Recirculation pump

    An option I've only recently thought of is installing a recirculation pump under the sink. I have an outlet down there, so it might be pretty straightforward. Perhaps if I do a good job insulating the kitchen supply pipe in the basement, the loss would be minimized.

    What are the relative efficiencies of #2 and #3? I'm leaning towards #3, with attention paid to the insulation on that home run. The water heater is an 80gal Whirlpool energy-smart water heater (3" insulation), although for a recirc pump, I think all that matters is the energy loss in the recirc loop and the resistance heat energy required to replace it.

    In retrospect, I really wish I'd installed a traditional supply trunk, designed from the beginning to have a single recirculation pump in the furthest fixture. Well, it's too late now - I have home runs in the walls and that's not getting changed.

    - Chris
    Last edited: Feb 2, 2013
  2. Terry

    Terry Administrator Staff Member

    Messages:
    14,818
    Location:
    Bothell, Washington
    190 degree water to a kitchen faucet would be a bit crazy.
    And the instant hot is only good for a few cups of hot water. It's not going to wash a sink full of dishes.

    The recirc makes the most sense. They make a remote system that will fit under the kitchen sink, or you can install one at the water heater.

    Putting a small remote water heater at the kitchen sink would mean running power there too. They also have relief lines that need to be drained. Way too much work, and most of those are just six gallons. Still pretty small for a kitchen.
  3. Hackneyplumbing

    Hackneyplumbing Homeowner

    Messages:
    66
    Location:
    Alabama
    He cant do a recirc system with his existing piping. He used a homerun system.

    He could of course do a recirc to the k-sink by adding a pump and a line back to the heater but that would only solve the problem at the one fixture. If thats accceptable and I assume it would be considering he is debating adding a small tank type water heater at the K-sink.

    I'm not a fan of the homerun hot water system.

    If he did the 6 gal tank and piped it in series with his large water heater the hot water would arrive before the smaller tank ran out of hot h2o.
    Last edited: Feb 11, 2013
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,832
    Location:
    New England
    A RedyTemp recirc unit would take less than 10-minutes to install under the sink. It's not the least expensive method. They make it fairly easy to control it multiple ways...run constantly when required; run on a timer; a push-button momentary timed run. Unless you have a dedicated return line, it pushes (as all retrofit ones) hot back through a cross-over into the cold line. They all have some sort of aquastat to shut it off when it reaches a certain temp (often, in the 105-110 degree range), so the cold isn't horribly hot. This is the bad part of the equation. The RedyTemp is the only one I know of that is adjustable. I have mine set to shut off when the water is just warm, but hot is nearby and available quickly. This minimizes how much 'hot' water gets pushed into the cold line. In my case, running things normally, I have it at the end of the hot water run, so everything else gets hot fairly quickly. It won't work that way the way yours is plumbed.

    If you can add a dedicated return line, then the hot in the cold line issue goes away. You can use the RedyTemp unit that way, too, if you wish. WHen I bought mine, they only had one model, they now have several, and the price and options may offer something that would work better in your case.

    Anyway, no cutting of pipes, or adding on things, essentially, disconnect the hoses from the shutoffs, connect them to the outlet of the RedyTemp. Add new lines between the shutoffs to the inlet to the RedyTemp, and plug it in, and it's done. Setting an optional timer or other control is optional (and you're not tied to it, it's just a plug-in timer or control). There's one other control...an adjustable aquastat you can set that tells the thing when you want it to shut off after having reached the set temperature of the hot water.

    Running a recirc system on a timer has been shown to save money verses wasting several gallons of hot water each time a tap is needed when you take into account the water heating costs, water costs, sewer, and electricity to run the unit. In any case, it's cost effective to insulate the supply line whenever possible when running recirc, and near the WH otherwise.
  5. Hackneyplumbing

    Hackneyplumbing Homeowner

    Messages:
    66
    Location:
    Alabama
    Every time a homeowner thinks a job takes 10 minutes is usually when I make the most money. Lol
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,832
    Location:
    New England
    Have you ever installed a RedyTemp unit? It attaches to the shutoffs underneath the sink via supplied hoses. Those that came off the shutoffs, go to the outlet of the RedyTemp. Plug it in, and it's done. It might take longer to clear room under the sink than it takes to install it, well, you might need a wrench or pliers to tighten or loosen the hoses, and that could take who knows how long. The thing is REALLY easy to install especially since he said there is already power available. That could add considerably to the time if it weren't there.

    I HAVE one and HAVE installed it...and that's about what it took. CHeck out this page...http://www.redytemp.com/howtoinstallhotwater/howtoinstallhotwatercirculator.htm
    Last edited: Feb 12, 2013
  7. Hackneyplumbing

    Hackneyplumbing Homeowner

    Messages:
    66
    Location:
    Alabama
    Iif its the one that uses the cold water line as the return....well thats not what I call a hot water recirculator........I call that a work around and a major hot water waster.

    Everyone is so worried about being "green" and then their answer is very wasteful. Nothing compensates for POOR plumbing design......throw all the money at it you want.
    Thats just my opinion.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,832
    Location:
    New England
    How many homes are built with dedicated return lines for recirculation? Few (it may be more common today). Whether one can be added without tearing up the house or not depends on many things, but would certainly be MUCH more expensive should you have to tear things up verses the energy and materials cost of a retrofit system. The way I have mine setup, and this is unique to the RedyTemp, is that everything else is closer to the WH than the vanity where it is located. SO, they have hot water almost instantly. At the sink, because I have it adjusted to only get warm there rather than hot all the other systems do, flushing the toilet is enough to purge that warm water. Most of the time, you don't even have to run the hot to wash your hands if you haven't flushed, but if you do need cold, you're wasting cold, unheated water for the most part, verses hot water.

    Now, should it have been designed in when the house was built? Certainly, even if it wasn't used, it would be nice to have the option.
  9. Hackneyplumbing

    Hackneyplumbing Homeowner

    Messages:
    66
    Location:
    Alabama
    The guys post is flawed anyway. It doesn't add up. He claims to have 35' of 1/2" pex between the water heater and the kitchen sink.......well 1/2" pex over a 35' run would hold about a 1/3 of a gallon of water. Thats not much to void before the hot gets there.

    If he really only has 35' of 1/2" pex in that run then I suspect his problem is with how much water the larger piping of the manifold is holding.

    I suggest do two things before adding any appurtenances to his plumbing system. Relocate the hot connection for the hot water pipe to the kitchen sink as close to the outlet of the water heater as possible. And number two if that doesn't help is to remove any flow restrictors of the faucet.

    I would do a simple test to find the problem. After a long period of inactivity of hot water use,have a person turn the hot water on at the K-sink while you have your hand on the pipe run just after it leaves the manifold. See how long it takes to get hot water to the beginning of the 1/2" run. I think thats where the problem is. The manifold is taking too long to purge......not the 1/2" line.

    Thats the best I can do sitting on my sofa. LOL
    Last edited: Feb 12, 2013
  10. chrispitude

    chrispitude New Member

    Messages:
    3
    Location:
    Allentown, PA
    I think you might be on to something here. I hadn't considered the volume of the manifold and upstream supply plumbing to it.

    Plus, there might be an additional factor... The other night, I pulled hot water at our upstairs master bath sink. I swear I got hot water quicker there than at the downstairs kitchen sink! The bathroom easily has to have another 20' of run.

    The bathroom sink fixture has two separate hot/water handles, while the kitchen sink fixture (a Delta Leland) uses a single handle that selects hot/cold/mix:

    http://www.amazon.com/Delta-9178-SS-DST-Pull-Down-Kitchen-Stainless/dp/B0040YXMYS

    When we first moved in, the water never got fully hot at the kitchen sink. We notified the plumber and he adjusted the anti-scald valve from its factory setting. He said there was no further adjustment, but I'm wondering if there is still some inherent cold-mixing happening in the fixture that adds delay the hot water arrival. I think some experimentation is in order to evaluate this aspect.

    Another thought is brewing in my head. Perhaps I could add recirculation to the dead end of the hot water manifold to keep the manifold hot at all times. If this supply volume really is a significant factor (and now I suspect it is) compared to the home run volume, I could significantly improve the hot water arrival times to all 1/2" home runs in the house...

    You guys are awesome. More to come.
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