Small insulated hot water storage tanks

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Klaus Franbrau

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Jun 29, 2024
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Location
Tucson, AZ
Hi,

I am considering using point of use hot water heaters to get instant on hot water. But it occurs to me it's a bit overkill for my situation and introduces some items that will require maintenance. (Edit: to be clear this is what I am trying avoid.) (Edit: Note my concern is maintenance, not cost)

It occurs to me that an insulated tank should be sufficient. If insulated to the same level as a hot water heater it should hold sufficient temperature for my purposes for nearly a day. (Edit: to be clear this is what I want. Simple storage tanks, not heaters.)

The ideal tank for my purposes would just be five gallons with both an inlet and an outlet (so the usual thermal expansion tanks don't work) and a drain for cleaning would be useful. Even better if the outlet drains from the top of the tank.

I'm having trouble googling for such a thing so I either have the wrong keywords or this isn't a good approach. Any idea? (Edit: For clarity, If you know why this isn't a good approach please post that)

Edit: So, is there a reason why this is a bad or uncommon idea? If there is a concern that the storage tanks would dip below 120 and might be bacteria breeding grounds I could use a single recirculating pump that runs once or twice a day to clear the tanks and reheat their water.
 
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Curiosity has got the better of me. Why are you trying to avoid the option that is readily available and the most practical way to do what you're wanting to do? A point of use water heater will keep the water hot and ready for use and don't use much energy to do it. I have never seen a storage tank like what you're describing. You most likely will have to fabricate one which can get expensive. Plus you still will have a long wait for hot water unless you have used it in the last couple of hours. I would go with a point of use heater or have a recirculation loop installed.
 
Because it introduces items that will require more maintenance. If I am wrong about that, I'd like to know.

And I don't understand why I would have a long wait for hot water if it insulated as well as a hot water heater. My current bottom of the line water heater has kept water sufficiently hot for a full day and it isn't even a modern one that would typically store at 140, it's at 120.

I can fabricate this and BTW note that cost is not my concern, it's future maintenance. And I can fabricate these, though I don't know if that would meet code, I prefer to buy.
 
You need to be careful about your assumptions. By your description, I'm assuming you have turned off your water heater for a day and you have found that the water is still hot.

However, the time it takes 5 gallons of 120-degree water to cool will be significantly less than it takes for 40 gallons of water in an equally insulated tank. Now when the 5-gallon tank is cooled, let's say down to 95 degrees, you will be bringing in 120-degree water to mix with that cooler 5 gallons of water. At that point, the temperature of your hot water going to your fixture will initially be 95 degrees. Then, as the water is mixing inside the tank, the hot water temperature will slowly increase to 120 degrees. It will take around 3 displacements, or 15 gallons of water, until you can get 120-degree water to your fixture.
If you don't like instant hot water heaters, like me, a better choice would be a small mini-tank electric water heater and install it at your point of use. Just pipe your existing hot water line into the mini-tank inlet. It will provide you with "instant" hot water and you will not experience any noticeable temperature drop as you use hot water. You could install it and turn it off, but I don't think you will be leaving it off for the reasons above.
Here's one from Amazon. I have no idea if it is any good, but this is just an example or a mini-tank water heater.
1719774326178.png
 
Thanks. That's a good point. But starting at 95 is still far better than what I experience now. That specific heater you cited is acceptable in my current specifications. That will indeed give near perfect performance and it's probably cheaper than the alternative I'm considering but I'm still wondering how often a heater vs a tank will need maintenance (or replacement).
 
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No maintenance to speak of unless mineral content is very high. So, NO maintenance.
The how long: LUCK. Major name brands preferred vs chinese. Warranty might serve you well (model with factory will be a pro-rated deal).
You do need to run the T&P to the exterior and we always install a drain pan run to exterior as well.
Note, that the delivered water will be mixing with incoming cold and you will start running tepid at 70% of the gallon capacity.
I doubt they will stay hot if not powered...mfrs rarely even list the R-value. Foam is typical insulation but look for it.
For set and forget: HTP brand is the best, with stainless steel tank, no anode rod needed, 2" foam and 10 yr. tank
 
Klaus Franbrau said:
Because it introduces items that will require more maintenance. If I am wrong about that, I'd like to know.

And I don't understand why I would have a long wait for hot water if it insulated as well as a hot water heater. My current bottom of the line water heater has kept water sufficiently hot for a full day and it isn't even a modern one that would typically store at 140, it's at 120.

I can fabricate this and BTW note that cost is not my concern, it's future maintenance. And I can fabricate these, though I don't know if that would meet code, I prefer to buy.
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So let me get a few things straight here:

1. Cost is not an object
2. Maintenance is an object.

As pointed out by others, a small point of use hot water heater will solve your problem. To the best of my knowledge they are all electric which means any "maintenance" is basically non-existent. You are not going to be flushing it, and you are not going to be changing anodes in it. If it fails, you replace it--you do NOT spend any time or money trying to fix it. THROW IT OUT and get new.

The pros can correct me here but I have a suspicion that if you fabricate and put your home-made insulated water tank on a potable water system, it won't been code unless it has some kind of certification like NSF or similar.
 
In case someone comes along with the same question I'm asking this is the closest thing I've found to my goal but obviously they aren't targeting my application:

https://www.bockwaterheaters.com/30st.html

To answer a few points in latest posts:

I am in a high mineral area.

Replacing the heater counts as maintenance to me. I really am going for low maintenance.

And 10" of foam is no problem at all if I were to go a DIY approach (which I'm not planning to).
 
There’s no free lunch, if you consider replacement as maintenance. Pick your poison and install it or live with the inconvenience of waiting for hot water.
 
Klaus Franbrau said:
In case someone comes along with the same question I'm asking this is the closest thing I've found to my goal but obviously they aren't targeting my application:

https://www.bockwaterheaters.com/30st.html

To answer a few points in latest posts:

I am in a high mineral area.

Replacing the heater counts as maintenance to me. I really am going for low maintenance.

And 10" of foam is no problem at all if I were to go a DIY approach (which I'm not planning to).
Click to expand...
I think if you go with a 30-gallon non-heated tank, you are going to exacerbate your problem. That tank will cool down some time. and at that point, you will need to put like 90 gallons of hot water into the that tank to get hot water out of it. And before you can do that, your 40- or 50-gallon water heater will be out of hot water, so you will never get hot water to the fixture.

To accomplish what you want, you MUST use a heated water tank at your point of service.
 
If you bought a storage only heater you would have to have a circulator pump and and thermostat to keep the storage tank hot.

It’s not like you can install a storage tank and fill it with hot water and it stay hot.

Get a small tank with element and thermostat and install it close to your point of use in series with your existing water heater. That’s the best way IMO if it’s possible.
 
So which system requires the least amount of maintenance? A pump that circulates hot water back to your existing water heater keeping the loop hot, or a small 4–5-gallon electric water heater at your point of service?

I think everyone providing information on this forum is saying the small water heater is the best choice for your need. If you have multiple service points you are concerned about, then the circulating system would probably be the best choice. But apparently you have only one place that you need/want relatively instant hot water, so either a small water heater or a tankless. But tankless water heaters require more maintenance, IMHO.
 
I'm not going with that 30 gallon tank. That's what I meant by "not targeting my application". Those are for much larger operations. But it illustrates what I am trying to accomplish, basically the same thing that large central boiler applications use. I'm looking for five gallons as stated in my OP.

And I'm not planning for recirculation. Normal use will refill it frequently. I don't care if it runs cold the first time I'm back from a vacation.

Edit: and I have two, possibly three, locations that may need this.
 
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Klaus Franbrau said:
I'm not going with that 30 gallon tank. That's what I meant by "not targeting my application". Those are for much larger operations. But it illustrates what I am trying to accomplish, basically the same thing that large central boiler applications use. I'm looking for five gallons as stated in my OP.

And I'm not planning for recirculation. Normal use will refill it frequently. I don't care if it runs cold the first time I'm back from a vacation.
Click to expand...
Ok
 
Klaus Franbrau said:
I'm not going with that 30 gallon tank. That's what I meant by "not targeting my application". Those are for much larger operations. But it illustrates what I am trying to accomplish, basically the same thing that large central boiler applications use. I'm looking for five gallons as stated in my OP.

And I'm not planning for recirculation. Normal use will refill it frequently. I don't care if it runs cold the first time I'm back from a vacation.

Edit: and I have two, possibly three, locations that may need this.
Click to expand...
Good luck. Keep us posted.
 
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