If you are doing this yourself, when you purchace your new water heater be sure you also get a new pressure temperature relief valve and when you plumb it in do not use regular PVC. Some areas allow the use of CPVC or PEX and others require metal.

As long as you are replacing the water heater, you may want to consider a short fat style. My next water heater is going to be of that variety with an overflow pan mounted on a solid table which will be screwed to the basement floor. Just be sure the pressure valve tubing runs down to within inches of the floor so that in the event of pressure release you don't get sprayed by hot water bouncing off the drip pan or table.

My next high efficiency furnace will be one of the short compact Rheems mounted on a steel table which will be screwed to the basement floor. This will make filter changing, blower motor oiling, and general yearly testing and cleaning easier. Mounted higher also keeps it farther away from the humid basement floor.

Bountyhunter

Short and fat seems like a great idea. Lower surface area to volume ratio, which should help with the efficiency. Spherical would be ideal, but also too expensive to make.

I would want one big enough so that I can set the temp just a little above comfortable shower temperature, without running out after 2 long showers (or one extra-long shower with 2 people, <img src="/images/graemlins/wink.gif" alt="" /> <img src="/images/graemlins/wink.gif" alt="" /> ). That would seem to me to be the most efficient. My washer and dishwasher both have internal heaters to bring their temperature up to what they need.

Theoretically, what would be the most energy efficient is "on demand" at each faucet. Then you don't have a tank of hot water sitting around waiting to be used, radiating energy. I understand that's how it's done in Europe in some places, but that's not the American way.

While the on demand system will be more energy efficient, you also have to consider the initial start-up cost in the equation. If the smaller waterheaters work similarly (with a small tank near the point of use), manufacturing requirements to make the smaller tanks may make them significantly more expensive for the capacity. Locally a 40 gallon waterheater is $100-$300. A tankless point of use costs $200 each. The prices are from the Lowe's website and is based on the store nearest my zipcode YMMV.

Benton,

Tankless, point-of-use, instantaneous - whatever term the salesrep uses - are difficult to apply well in a retro-fit to a typical upper MidWest house. I'm neither for or against them, but do some hard homework before deciding. I'm on the regulatory side of the business, and we open-mindedly see everything under the sun; what works and what doesn't work. Some things to look into:

1. What is the water temperature of your water supply in the dead of winter? We have VERY cold supply water in my town (Mississippi River source) in wintertime; as a practical matter yours can't be colder (but probably isn't warmer) and that has an unbelievable impact on how much hot water you can wring out of those puppies. You need to review ALL the rate-of-rise data and size for the largest winter time situation - usually showering. Here (south of you) the size required at least doubles from summer to winter conditions.

2. The efficiency information is usually over-hyped and you need to read the fine print. At full output they require an enormous energy input. At trickle-of-warm water rates (like shaving), most of them are fairly inefficient. Heat exchanger design is optimized for certain conditions, and the device's automatic energy controls vary from "off-or-on" to some number of discrete steps or levels, depending on the specific model. They simply cannot be universally efficient through a large range of demand situations.

3. The best way to take advantage of these is to put one at every point-of-use location - every shower/tub, every lavatory, etc. That's a heck of a lot simpler to do with a new house as it's being built than with a retrofit to an exisiting house. There are many compromises made when they are used as a substitute for a storage water heater in a house that was designed for a storage water heater.

4. In an efficiency flat with a shower/tub, lavatory, and kitchen sink all on a common wall or plumbing chase, located within a few feet of each other, they make a great deal of sense. In a flat with pay-as-you-go energy metering, they make sense from the landlord's point of view. They are very difficult to adapt to typical Western lifestyles, especially USA lifestyles in typical USA houses unless you put lots of properly-sized units all over the house. And you will NOT recover those costs in increased efficiency over a normal lifetime if you do it that way. Even extra-high efficiency storage tank heaters take a while to pay back the increased cost - the math is simple; check yourself.

If you want to really make a huge dent in your home energy use (assuming your home is reasonably well insulated and draft-sealed already), look into ground source heat pumps. If you choose, they can also provide all your domestic hotwater needs, and the industry in the US is finally mature. They eliminated the big problem (choice of anti-freeze for the working fluid) some time back, so take any apocryphal stories that armchair experts may relate to you with a grain of salt. The upfront costs on a re-fit are scary as heck - we're talking home equity loan here for most folks - but the return-on-investment times are typically extremely short unless you have unusual geological circumstances (BEDROCK). It's almost absurd that new homes are not nearly universally built with ground source heat pumps in this area - especially in new subdivisions, when a common well field can be installed very economically on a per-house basis.

OK; this is ETS and I'm simply not going to add any more to this thread or any other home-improvement stuff, Campfire forum or not.

I hope this is food for thought, and helpful to you.

Tom

You won't need ANY anodes if you install the unit with dieclectric fittings. The differences in potential (electric) between dissimilar metals causes premature corrosion of hot water heaters...i.e., iron to copper, copper to aluminum, etc.

Having said that, an anode doesn't hurt <img src="/images/graemlins/smile.gif" alt="" />

The sacrificial anodes in water heaters are designed to reduce corrosion in the water jacket and really have no bearing on the pipe connections outside of the tank.

The dielectric fittings are a good idea for the tank connections in the case of dissimilar metals and will make the outside connections less likely to corrode and leak, but the internal anode is for the small bits and pieces that make it into the tank and may affect the tank itself. The sacrificial anode is softer and easier to attack and protects the tank by letting itself be eaten by the chemical or electrical processes that may occur in the tank water.

Bountyhunter

AyersGT:

I have to disagree with your view on your post.

This forum IS about practical survival and just living day to day with some of the emergencies that can affect us all is reasonable.

I don't run the site and my view may not be valid, but my view is reasonable, practical, and has no "RAMBOSQUE" tilt to it.

Bountyhunter

Pete,

Sure - but *I* don't want to yak about it anymore was my point, so I'm not.

[over-the-shoulder-toss] ...your anode/dielectric comments are exactly right. Using dielectric pipe unions is a good idea - at the very worst harmless, and possibly required by local codes - but have nothing to do with tank anodes. The magnesium anodes are "commercial grade", work better than the cheaper aluminum anodes, and are less worriesome re: adding trace amounts of aluminium salts to the potable water for those who are concerned about the matter... and now I'm quits on the topic! (it's too work-related for my mood right now). Y'all go ahead and discuss home improvement all you want, NP. <img src="/images/graemlins/cool.gif" alt="" /> [lurk mode on]

Tom

Are you talking about GMO heaters ??

Aaaarrrrghhhhh................;;;

<img src="/images/graemlins/grin.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" />