OT: Separate hot and cold valves on kitchen taps save energy.

Robatoy · 2011-06-05T16:20:59+00:00

Just a hunch mind you, but at my house, that Delta faucet single-leveris always parked in the middle position.When any of us need water we push it to open, but I seldom see it thenturned to the right which would give us only cold water.Now, if we fill a pot of water, we do push it to the right, butinitially 'some' hot water will be released as the valve is opened.I felt the hotwater tank outlet line heat up as the water was drawnwith the valve 'in the middle'.Add up all the single lever taps on the planet, and the bad habit ofnot turning the valve handle to the 'cold' position, and you gotyourself another source of wasted energy that can only lead to theoceans going up another foot.I say: OUTLAW single lever taps.

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Eric 15 years ago

You're right about the long runs, but I'd argue that a PEX remote manifold, if located/done correctly, should improve your delivery system even in those cases. As I said in the beginning, easier to do in new construction, mostly difficult, and usually expensive to effect in most retrofits ... which is why it isn't often done, and IME results in the biggest cause of user dissatisfaction with tankless installations.

Close to the endpoint (your "right at the tap") is pretty much how Europe has operated for decades, and very successfully. Pumps and a loop system, if properly implemented, also seem to work very well, although I haven't built one that way personally.

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I could see using a low temperature preheat (maybe NG or solar) to take the edge off the initial water heating and then a small (maybe electric) booster to give the final temperature at the faucet. Probably too much installation expense though.

I have many of my runs disconnected from my hot manifold to keep more frequent circulation going in the trunk runs. I was waiting so long for hot water it was painful. I want to put my air handler on the end of that run yet, to keep hot water close to faucets, except it will not help in the winter and the legal limit of 60C makes an upstairs warm-up each morning a little too lengthy. I did add it to the feed of the manifold and that cut a few seconds off the time delay. I still have access to most of my PEX as the basement ceiling is removable tiles or open. Not done experimenting yet.

The PEX really puzzles me over my old house copper system. I have less length to the farthest faucet, and the PEX is supposed to be smaller ID and it still seems to take double the time the copper house did for hot water to hit the end faucet??? Maybe I am just watching too closely. It also seems to cool off much faster than copper pipe so you start with room temp every time. I was thinking it should be the other way around. Meanwhile a neighbour installed all copper and a circ pump and has hot water within 2 seconds anywhere. GRRRRR...

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Eric 15 years ago

Watch that paraphrased Google knowledge, it'll bite you in the butt just like your plumbing salesman ...

Water temperature and source makes no difference to a manifold delivery system itself, hot or cold, tank or tankless.

With a PEX mainfold system, properly located and installed, the water in the usual 3/8" tubing has a higher water velocity, and the water, hot or cold, is delivered much faster than with a conventional piping system, tank or tankless, and with a lower volume in the tubing ... albeit not much more "green" on that score.

Once again, proper planning and installation to the forefront. ====================

The tankless water heater problems are not addressed with design techniques of water delivery systems. Hot and cold water have different requirements for delivery. Cold water can go to Timbuktu and back and there isn't much ill effect on it. Hot water needs to be delivered before it cools off.

That may be the biggest problem with this stuff here. 1/2" is the standard and 3/8" is very uncommon and more difficult to obtain. There may even be a code issue as PEX is new on the scene.

We do not use 3/8" tubing. We only have 1/2" PEX pipe used for plumbing. Plumbing uses pipe sizes, not tubing. 3/8" PEX pipe could make more sense to fill less reservoir with hot water before delivery. I am not familiar with an code issues on the smaller size.

I only know the latest system delivers hot water much more efficiently without the manifold and longer lengths of reservoir.

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Swingman 15 years ago

Disagree... they can be, and they should be if you have the opportunity to do so.

That's not what you said ... You specifically state that about a manifold system, which I have proven in practice to not be the case with proper attention to detail.

A 1/8" diameter difference in pipe is significantly and mathematically different as far as flow and volume characteristics.

The tail that wags the dog with diameter is the fixture requirements ... There is not a one size fits all that will cover all bases and make everyone happy.

One of the jurisdictions I build in does not allow PEX ... It is why I'm so painfully aware of the differences in tankless delivery that are possible with a PEX manifold system when called for.

Every plumbing situation is unique (even in tract homes with supposedly identical plumbing schemes) so the above is not surprising.

Again, the toughest thing to get correct is tankless in a retrofit/remodel, much easier to design, install, tweak in new construction, there are simply too many shoe merchants and ribbon clerks in the game, and even plumbers will not agree on much of it.

And again, it is why I do not have tankless in my own home to this day, which I built before the technology was readily available locally.

That said, the next new house, and the ones after that, that I build will more than likely be spec'd for tankless as long as it is in a jurisdiction that allows me insure that a design for that particular and unique situation can be forthcoming, and that it will satisfy me, and the customer ... anyone who knows me will attest to the fact that I abhor callbacks.... Nuff said.

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Swingman 15 years ago

Did you ever go back, as a check, and re-spec your house as if were a new installation?

I don't think they were strictly for builder accounts, but my suppliers had downloadable spreadsheet based software that would allow you to put in all your parameters, ambient ground water temps, list all bath and kitchen fixtures and their flow requirements, etc., and spec a general idea for a recommended tankless unit.

Might give you a start point in sussing out the reasons .... Just a thought.

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John G 15 years ago

Eric presented the following explanation :

Circulating pumps would seem to defeat any effort to reduce power usage as they keep sending hot water around the loop to cool and then be reheated even when there is no usage so instead of wasting one pipe full of cold water that heat is being lost all the time. Of course the water is saved but the heat (heating power ) is lost. Choice is on the user I guess.