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Thread: Switch from Tank to Multiple Point-of-Use Tankless, Crazy?

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    Default Switch from Tank to Multiple Point-of-Use Tankless, Crazy?

    First time posting here, but I've learned a lot lurking in the background so far. Now it is my turn for some questions!...

    Looks like I'll be needing to replace my old and sclerotic galvanized pipes with something new. I had a shut-off valve added to a basement toilet last week and the water pressure has just never recovered (even after cleaning screens, etc.). The house is from 1952....and I would put money on the galvanized being original. So, I think it's safe to say the galvanized has served its useful life...and then some!

    I'm pretty set on PEX of some sort (intrigued by the new fitting system that iplumb.tv is starting to sell), largely because I can do some of it myself and it's (comparatively) easy to work with. I've got a plumber in town who is quite good (all the other tradespeople use him, for instance), and he is totally open to me paying him for design and consulting assistance at his hourly rate. So, this would be a DIY project, but not a complete do-it-myself type of thing. The plumbed part of my house is small (kitchen with 1 faucet that shares supply with a high-efficiency dishwasher; single toilet in basement; bathroom w/ 1 shower/tub, toilet and 1 faucet and, immediately beneath it in the basement, HE washer and another faucet; oh, and two hose bibs) and about 99% of the system is easily accessible and totally visible from the basement.

    My question: is there some reason I should not just ditch my fairly mediocre (and probably 12 years old) gas-fired tank water heater AND replace it with ONLY point-of-use, electric tankless unit? I ask for a couple reasons. The big one is that my water heater is basically in the farthest corner of the basement away from everything needing hot water. So, the cold supply and hot supply have to run the full length of the house to service my kitchen (which is literally right above the service line for the house). Secondly my other two hot water areas (the bathroom as well as the laundry area) are stacked on top of each other as well. Finally, mounting and connecting (the plumbing part) an electric tankless doesn't worry me too much (they are small), and I would pay an electrician to hook them up (and I believe I have the needed unused circuits to give them enough juice).

    The appeal here as a DIY repiping of the whole house is that I would massively cut down on the number of water lines running around under the house. I would use a small, under counter heater in the kitchen and a mid-size heater in the basement for the basement/bath region.

    Does this seem crazy? A bad idea? Any suggestions?

    Many thanks!

  2. #2
    Plumbing Designer FloridaOrange's Avatar
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    Electric tankless suck, if you go tankless gas is the way to go. Multiple electric tankless will likely require a bigger service than your house currently has.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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    Quote Originally Posted by FloridaOrange View Post
    Electric tankless suck, if you go tankless gas is the way to go. Multiple electric tankless will likely require a bigger service than your house currently has.
    Matt -- Thanks for such a quick response! Yeah, I was never intrigued by electric tankless when I was thinking about whole-house tankless systems. However, with a "distributed tankless" setup (as I guess we could call it?), I thought that maybe the disadvantages of the electric wouldn't be as severe. And, if I went whole-house tankless, I would still have these long runs (the tankless unit would need to be right around the location of the current tank, because of venting).

    But your view is that electric tankless of any sort (except maybe the single faucet ones) is not so good?

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    Plumbing Designer FloridaOrange's Avatar
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    Electric takes alot of more power to heat the water up and I've seen/heard of alot die or become troublesome after a two years or so. IMO they usually don't seem to be worth it unless you don't have any other choice.

    Are you going with a manibloc (home run) setup or a branch system. If you go branch system you could put in a type of recirc system back to the tank. If you insulate the tank as well as the hw side and you use a timer and aquastat you could have a pretty efficient system and have hw on demand.
    Last edited by FloridaOrange; 10-15-2009 at 06:05 PM.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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    In the Trades Gary Swart's Avatar
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    If your concern is having instant hot water, a recirculating system for a new gas water heater would make more sense. It would be cheaper to install and certainly cheaper to operate. Tankless heaters have a handful of fierce supporters, but to most to use, they haven't proven to be that great.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default heater

    For your purposes an electric tank type heater near the bathrooms would do the same job and would be much less expensive. Point of use water heaters are not the same as tankless heaters. They have much less flow capacity and are essentially useless for anything other than a faucet where you wash your hands, (and you had better not need a lot of volume to do that either).

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    DIY Senior Member jastori's Avatar
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    How about a new gas tank water heater that is located in the basement, but closer to the kitchen and baths? If you get a new high-effeciency heater, it can be vented with PVC out the wall, so you should should be able to locate it more conveniently.

    Electricity typically costs much more than gas to heat water. A properly sized gas tank unit will be much less expensive to install than multiple tankless units. The cost of running a little extra pex is almost trivial compared with the cost of the tankless heaters. If you really care about instant hot water without wait, you can install recirculation, but that may not be necessary if the heater is closer to the point of use.
    Last edited by jastori; 10-16-2009 at 07:59 AM.

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    DIY Junior Member turkeyvulture's Avatar
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    Have you considered 3/8" pex for individual hot feeds from a manifold to decrease the hot water wait time and waste? Do a litte math. 3/8" pex takes about half the time to deliver hot water compared with an equal length of 1/2" copper. It will actually be a lot less than that, because a copper system will need to empty some length of 3/4" pipe which has twice as much cross sectional areas as 1/2, The pex is 3/8" all the way. Also, the total pex path may be shorter since you can run direct from the manifold without any detours to service other fixtures.

    The pressure loss for 50' of 3/8" pex is about 8 psi at 1.5 gpm, so you will still have about 40 psi or so at the fixture, depending on what you started with.

    No fooling around with extra recirc. pumps and expensive tankless units, etc.

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