Mini tank water heater for longevity
Is there such a thing as a long-life mini-tank water heater – so 2.5gal/4Gal tanks?
The Bosch mini-tanks seem a popular choice but the Amazon reviews are sobering. Of course reviews tend to swing negative because fewer people report success. Common issues seemed to be leaks developing after a year of so. It seemed that they are not expected to last beyond 3-5 years – significantly less than regular sized whole-house water heaters. They also need the anode rod replaced annually which is a high maintenance cost if there are several of them around the house. Stiebel Eltron seems a step up in quality but still the expected lifetime seems low and the anode rod needs regular replacement.
While these mini-tanks can save energy costs in some scenarios, there is also an environmental cost to continually replacing anode rods annually and the whole unit every few years.
Is there a brand of mini-tank water heater that’s focused on longevity rather than lowest-cost? I’m not considering tankless here due to a combination of cold winter water and limited power.
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Replies
HI there Bill -
Sorry, this is not an area of expertise I have. Hoping someone with that expertise can weigh in.
Peter
What is the reason for not just using a standard tank? There may be some other options, depending on what your circumstances are and what you're trying to achieve. It sounds like you're planning to put a mini tank at each point of use in a house, but it's not explicitly stated.
I have a rainwater system, presently used for irrigation and outdoor faucets, however I'm switching over laundry and toilet flushing to rainwater to increase utilization. The laundry is the issue. I can't (or at least I don't want to) connect the hot water tank to the washing machine so long as rainwater is connected to the cold inlet. Too much risk of cross-contamination IMO. (I actually don't know what the risk is, but it seems like a bad idea to me.) So a mini-tank to supply hot water to the laundry would work.
I'm also building an ADU which is also connected to the rainwater system so I'll install another mini-tank there. It will be a heat pump washer/dryer and being able to wash with hot water will improve performance.
Another reason for interest in mini-tanks relates to an idea to eventually switch the showers over to rainwater. It's not feasible at this at the moment as the City requirements for regular testing would make it too difficult to use rainwater in the showers. However that could always change in the future. My idea would be to switch the main hot water tank over to the rainwater system, then use mini-tanks for all bathroom basins, kitchen etc.
It might be that mini-tanks actually perform well, and that the negative Amazon reviews are are not typical, however, I have no way of knowing that. I'd think there must be some GBA readers who have used mini-tanks.
Bill,
If I'm not mistaken, most modern washing machines no longer even have a hot water connection. Even if they do, they heat the water themselves once it reaches them. They use too little water to rely on the heat not being lost in the pipes, and benefit from the precise temperature control only in-machine water heating can offer. Further, even if they did have a hot water inlet, a 2.5 or 4 gallon water heater would probably not have enough capacity (even the best energy-stars washer uses at least 10 gallons of water, last I checked).
As for showers, a 2.5 or 4 gallon tank would work only for the shortest showers, as even low-flow shower heads use at least a gallon a minute.
Bill,
There are several plumbing connections where there is a chance of cross contamination - outdoor hosebibs, clawfoot tubs, etc. - and the solution plumbing codes mandate are usually back-flow preventers. If you put one on the hot tap or line you can avoid the whole second tank problem.
I have one - about 10 years old and it gets > 5 years from an anode.
If you really don't want to worry, there are small marine heaters made from stainless.
Another option is to run the source water into a large water heater set to 75F and from there to POU instant heaters. Might reduce POU power by 45%.
Aedi
Washing machines have a hot water connection. Dishwashers have an internal booster heater used in some cycles. They too have a hot water connection, but not cold.
I can confirm that modern dishwashers do not actually require a hot water connection. Sometimes the installation manuals specify one, but if they are fed cold water they simply heat the water up themselves to the necessary temperature, perhaps extending the cycle time. Even the cheap, 5+ year old model our landlord put in our apartment does this. Most instruction manuals for dishwashers ask you to run hot water through the kitchen sink first, so that it is readily available to the dishwasher; however they also note that not doing so results in longer cycles (as they heat the water up). Some high end models actually benefit from a cold water connection, as different parts of the cycle use cold water to save energy. See this section from Miele's manual for their G4998SCVISF model:
"The dishwasher may be connected to a cold or hot water supply up to a
maximum of 140°F/60°C. For reduced energy consumption, we recommend a cold water connection. We recommend connection to a hot water supply only if it is economical, e. g. a solar-powered supply with re-circulation line. When connected to a hot water supply, all program phases which would otherwise be carried out with cold water will be carried out with hot water"
http://static.appliancesconnection.com/attachments/D5a4bc387cb269.pdf
Miele's washing machines operate a similar way. See their webpage:
https://www.miele.com.au/domestic/2676.htm?info=200003832-ZPV
Note that they specify that their hot water inlet, when available, can also be used for rain or well water, implicitly without first heating it.
I suspect washing machines operate similarly to dishwashers, in that if they get cold water, they will heat it until it reaches a specified temperature, perhaps extending the cycle. I would be very surprised if this was not the case, but it is possible with heat pump washer/driers, as they might not have an electric resistance element or heat the water with the heat pump.
Edit: Excluding top-loaders or other inefficient models, as they use enough hot water they can feasibly depend on the hot water connection.
Aedi,
I said dishwashers have a booster heater for some cycles. Please show me a clothes washer that doesn't have a hot water connection.
I was unable to find any washing machines entirely lacking hot water inlets for sale in the US, but as I noted, Miele's hot water inlet is strictly optional:
https://assets.ajmadison.com/ajmadison/itemdocs/W3048_us_manual.pdf
It seems that machines lacking a hot water inlet are more common in the European market, and are in fact the default. See:
https://www.whitegoodshelp.co.uk/cold-fill-washing-machines
Edit: That same website notes that washers that have both hot and cold connections can be connected to just cold water, and will heat the water themselves:
https://www.whitegoodshelp.co.uk/washing-machine-is-a-hot-and-cold-fill-but-i-only-have-a-cold-water-supply/
Again, I would be very surprised if any American model that has a water heater would not have similar capacities. Some websites allow you to show only models with integrated water heaters:
https://www.ajmadison.com/b.php/Front+Load%3BWater+Heater%3BWashers/N~37+4294846359+2788
I would email the company's customer support to verify that they would still function properly and not void the warranty though.
Patrick,
European appliances (at least the ones sold in Europe) are designed as Aedi described. American appliances are different.
European clothes washers just need a cold water connection. Almost all American clothes washers require both a hot and cold water connection.
[Later edit: It looks like Aedi and I were typing near simultaneously -- and were typing similar comments.]
This article seems to indicate they tested this Maytag washer with only cold water and that the machines internal heater warmed the water as needed. I read the install and owner’s manuals they did call for both hot and cold water connections and did not say how or when the heater would operator just that an indicator would light when it was operating.
http://solarhomestead.com/clothes-washers-for-an-off-grid-home/
Walta