Under-Sink Mini-Tank Water Heater

[ERD50]

Quote:

Originally Posted by Telly ... So it would seem if the mini-tank's capacity is less than some X times of the amount of the "slug" of cold water due to sitting in the pipes cooling off from the main heater, then the faucet water temperature profile versus time will be: Hot -> Cold-> Hot If the mini-tank's capacity was many times the amount of the slug, then it would seem that even with cold pipe water mixing in for the short while, there would be enough hot water stored in the mini-tank to mix in with and minimize the cooling effect of the input slug. I'm just thinking as I'm typing...

Agreed. I would expect the temperature of a small tank to drop pretty quickly as the cold water mixes. You get significant stratification in a large tank, very little in a small tank like that, with those kinds of flows.

Quote:

Originally Posted by zinger1457 Are you doing this to conserve water or save money? If it's to save money I doubt you'll ever re-coop the cost of whatever system you choose. ...

This too. I sometimes think of doing something like this in our bathroom, and like pb4uski mentioned, it could be improved with a mixing valve (you could keep the little tank set at a higher temp, therefore increasing its effective capacity).

But then I think abut all this, and I decide that occasionally waiting a minute for some hot water isn't really that big a hardship.

-ERD50

[pb4uski]

Quote:

Originally Posted by ERD50 ....But then I think abut all this, and I decide that occasionally waiting a minute for some hot water isn't really that big a hardship....

True, its in the "nice problem to have" category in the whole scheme of things, but in my case we also have a well and septic system so the water that flows into the drain while i'm waiting for the hot water to arrive is coming from my well (no big deal since I have plenty of water) and going into my leachfield (could be a bigger deal at some point).

[Bob Adams]

Quote:

Originally Posted by walkinwood We have the grundfos comfort system, but to back-fit it into an existing home, you'll need to make a change to your piping - something called a direct return.

Grundfos makes them for either new construction with a return line, or existing construction where the existing cold and hot water lines are used. The product number for existing construction is 595916 and can be seen here on Amazon Grundfos 595916 1/25 Horsepower Comfort Series Recirculator Pump - Amazon.com

[Bob Adams]

Quote:

Originally Posted by calmloki I think this is the hot ticket - hot water pretty much instantly at ALL points for the cost of keeping hot water in the pipes and some minimal pumping. Wonder if the cost isn't equal to the cost of having a couple gallons of hot sitting under the sink in a poorly insulated container. It was suggested to me when we did our place a dozen years ago - didn't do it, I just adjust what I'm doing to match the temperature changes.

Exactly, hot water everywhere, extremely compact, not much if any parts needed to install, and simple enough to do so that you can eliminate the high priced labor.

[TromboneAl]

New sink in, plenty of room for a mini-tank now:



My measurements show that I get hot water from the whole-house heater after 1.5 gallons flow through the faucet. So, for the first 1.5 gallons, I'll get hot from the mini, then from the main. When done, the mini will have hot water in it, so it will never have to heat up cold water.

I'm starting a new thread to get advice on which one to purchase.

[pb4uski]

But will you end up getting hot water from the mini followed by lukewarm water from the pipes between the mini and the whole house heater and then hot water from the whole-house heater?

Or will the lukewarm water and hot water from the mini be mixed together?