The real world isn't an easy place to be idealistic about hot water systems and what could be. Many compromises are made in cost, quality, expectation and education. Money and ego play a part as well. We'd like to daydream out loud for a bit and share some 'what could be's" and 'only if's" as they relate to hot water.
The ideal water heating system would be supremely energy efficient. It would last as long as the building it was installed in. It would be a pleasure to live with. It would be absolutely safe and of course, the cost wouldn't be too much.
You're not going to get such an elegant system installed by a plumber who isn't thoroughly trained in hot water work, or one who may be more interested in bringing home the most dollars per job, rather than insuring your satisfaction. The challenge here is how to properly educate the workforce, not just in things technical, but also in business basics and management. Correctly trained plumbers wouldn't lose so much work to relatively unskilled (and possibly unsafe) handymen.
Fortunately, when it comes to efficiency and longevity, we have lots of examples from the past to help show us the way. In 1906, there were condensing water heaters which claimed 92% efficiency (most modern gas fired heaters are more like 60% efficient). Since these were point of use heaters, there were no distribution losses or waiting for hot water. These were 'bath heaters' and the downside is they weren't all that safe. There were also "U" tube heaters. In these gas fired, tank heaters, the flue went up, near the top, then turned 180 degrees and headed down again. It would exit near the bottom. This doubled the heat exchange area of the flue, but even better, stopped much of the standby loss gas heaters suffer from. Our daydream has modern hot water engineers looking at old designs like these in order to incorporate the good ideas from the past into today's heaters. We’ve collected a bunch of interesting old heaters which the General Society of Mechanics and Tradesmen in New York will be putting on permanent display. Hopefully it will serve as a resource to future hot water engineers and anyone who’s interested in hot water.
Have you heard of Monel? It’s a copper / nickel mix that is currently used on high end boat fittings. From the 1930s to the 1950s you could get water heaters made of Monel. These and copper tanks were often the last tank a homeowner would ever need to buy. Such long lived tanks are essentially not available now. Roughly 85% of the nine million or so water heaters made yearly are sold as replacements. The manufacturers seem convinced that low cost is the most important thing to buyers, so proven long lived tanks are just a memory. Our dream has manufacturers competing to produce the highest quality heater, just as their predecessors did, instead of competing to make the cheapest heater. There are exceptions, but they make up a tiny fraction of the market.
The cost of the hot water system needs to be put in perspective. Manufacturers and plumbers both compete on price, but how cost effective is something that needs more service and frequent replacement? End users would need to be educated in the hows and whys of life cycle costing, where all costs over time are taken into account. This is the only way to know what really is a good deal. This may be an area where government and other institutions could set a good example and help to retrain the home owning public. More demand for long lived equipment would help to make such equipment readily available at reasonable prices.
Just as there are rating systems for energy performance in new construction, we'd like to see the same thing done for hot water systems. Ratings could be based on total energy use per person, waiting times for hot water, etcetera. This could motivate plumbers to do better than just meet code. Gary Klein is working on that with his “hot water rectangle”, which is a way of looking at wet room placement in a building and being able to see in general just how efficient it may be. See: http://www.garykleinassociates.com/
Sediment is a problem in many modern heaters, particularly those with aluminum anode rods. One fix could be the "external flue" heater. This had a narrow flue wrapping completely around the tank instead of the central flue common in modern heaters. Aside from increased surface area for better heat transfer, this heater allowed the lower tank head to be domed down. Sediment would collect at the low point in the center and be easily removed by opening a drain valve attached there. With modern insulation, external flue heaters would have much lower standby losses, making them very attractive. Us moderns have to live with pounding and thumping in gas heaters because sediment is so hard to remove from today's tanks. Aluminum anodes contribute by adding a great volume of corrosion byproduct. Magnesium anodes (although slightly more expensive) used to be the norm and don't make such a mess.
In our daydream, metal distribution piping, stealing BTUs from the hot water and holding way too much water would be a relic of the inefficient past. Manifold systems using well insulated 3/8" PEX tubing (or even 1/4” tubing for short runs) would be the norm for medium sized and smaller homes. This method provides quick hot water delivery, has much less water waste, and is installed more like wiring than rigid pipe, making new construction simpler and retrofit much easier. Efficiency can be had with devices that use electronics, pumps and various other active things, but long term reliability is one of our goals. For example: You can cut standby heat loss from an electric water heater with a time clock or with heavy insulation. We would opt for the "nothing to go wrong" insulation first. Of course a timer could be added to keep the heater off during peak periods, but it IS one more thing to get out of whack.
In an effort to keep heat from being lost, we've paid a lot of attention to combustion efficiency and insulation, but then we let all that heat go down the drain. Going the extra distance to recapture those BTUs with drain line heat exchangers (which are now made for both vertical and horizontal applications) begins to make better sense as the actual costs, both monetary and otherwise become known. In our dream, long lived, efficient systems would have minimal environmental impact.
We've been watching the progress of a non-electric flue damper for some years. It is a simple and inexpensive device that fits under the draft hood and cuts standby losses at least thirty percent. That could amount to a huge savings, but somehow, the long and winding process of getting approvals, perhaps combined with egos and territorialism all conspire to keep the device off the market. It would be nice to see more regulators and industry representatives looking at the common good rather than their own turf. As energy and clean water grow ever more expensive, such turf wars must become less relevant. Now, if you put one of these dampers on an external flue heater, you'll have one simple and high performance water heater!
Please don't think we have pessimistic daydreams. All the necessary technology already exists. Together we have the talent and muscle necessary to make dreams of efficient, safe and easy to live with systems a reality. We are only lacking consensus of all the players.