Efficient Hot-Water Piping (2013) [pdf]
garykleinassociates.com
garykleinassociates.com
Plumbers are happy to just use whatever fittings, etc, to get pipe where it needs to go, and rarely, if ever, think about the losses caused as a result (i'm really not slagging on plumbers or the quality of work, i'm just saying the average plumber trying to get 4 homes done is trying to get 4 homes done, not sitting around calculating the most efficient layout for copper pipe when he discovers a stud in the way nobody planned for).
In the past two brand new houses i've lived in, done to the latest plumbing code, the amount of hilariously horribly copper layout is amazing.
(I'm sure anybody who does this for real has ridiculous horror stories).
Meanwhile, most pex layouts i've seen perform significantly better in practice just because they use less fittings. So the attempt to be "as horrible as copper" fails.
Also pex is a better insulator, so in the real world where pretty much no in-home copper is insulated, pex holds heat better.
So, yeah, i agree with the sentiment that well thought out, well structured copper works really well, that doesn't happen to be residential reality, and hasn't been for a long time. (it's possibly a commercial reality though)
Copper water pipes should always be insulated with at least 6 mm EPE sleeves or closed cell elastomeric foam sleeves (better). Even cold water pipes should be insulated at least in heated or high humidity spaces because of condensation that forms on the pipe.
Errr, i have used systems of pex with outside fittings forever. Yes, inside fittings suck. All of the manufacturers have been sued for leaking, etc.
"Copper water pipes should always be insulated with at least 6 mm EPE sleeves or closed cell elastomeric foam sleeves (better). Even cold water pipes should be insulated at least in heated or high humidity spaces because of condensation that forms on the pipe."
Yes, they should. But they very rarely in my experience (or they did a super shitty job) are unless the house was just built and you had a good code inspector
Speaking of which: I had always wondered why more plumbing isn't done with flexible hoses instead of this pipes. Hoses seemed like they'd be way easier to work with. Now my guess is that hoses generally have unnecessary curves no matter what and that this increases the pressure lost. Is that right?
They've perhaps fixed that by now, but the reputation is there.
And it turns out that an unexpected rupture of a water pipe can be very, very expensive indeed. Especially in a wood-framed structure with sheetrock. Especially if nobody's home.
So builders are generally very conservative with water pipe materials. Nobody wants to install the next PB disaster. Building supply companies are even more so; the PB lawsuit cost Shell a billion dollars.
Garden hoses are usually made from one of two materials: some kind of rubber (buna?) or PVC plasticized with phthalates. With hot water, neither of these will last even the 10 years that a lot of PB piping lasted, and the phthalates will leach out into the water and give it that garden-hose taste.
I don't think the curviness of hoses is generally enough to cause a significant pressure loss.
As noted in another comment, PEX is sort of flexible and hoselike, and is seeing a substantial amount of use for water piping nowadays.
Aside: due to the toxicity much of the lead pipe installations no longer exist, so modern pictures of lead pipe installations are exceedingly rare, but for the curious: https://www.nachi.org/forum/f22/lead-drain-supply-2105/
The snakelike nature of lead pipe is also immortalised in early cartoons and drawings.
You may enjoy reading some early plumbing books: https://archive.org/details/standardpractic00davigoog
Yes, PEX is the flexible tubing material you are thinking should exist.
PEX and sharkbite fittings are like magic - you can plug together arbitrarily complex water circuits and layouts as simply as building with legos.
I personally use copper piping for very long-lived installations and for simple, long runs. However, anything complex at the end of the line (irrigation, pump and well work, filter assemblies, etc.) transitions to PEX and shark bites.
It is particularly problematic in inaccessible areas (hidden behind drywall).
PEX compression fittings with coupled 'sticks' of straight PEX makes runs easier (not having to straighten out the 'coil').
Also, check out the Milwaukee PEX tool. Expensive, but awesome.
PS
In the first episode of Stranger Things, you can see the hot and cold PEX runs in the kitchen of the diner. Very progressive.
Here's a link to an informative and sensible video on SharkBite... https://www.youtube.com/watch?v=1E8X1VawLeE
First, you presumably don't want to put your Seebeck generators on the pipes that run hot water to your taps, because that would make the water coming out of the taps colder. That heat isn't waste energy; it's the effect you were trying to achieve by heating the water! You'll have to put the Seebeck generators on your drainpipes only. But usually it's the supply pipes that corrode, not the drains.
That aside, I am guessing it's going to be hard to passively pull out so much heat from the water as to make a noticeable difference in the corrosion rate. Remember that the temperature difference has to remain large enough to keep driving the current through the load. And, in order to do it, you need to hook up the Seebeck generators to the pipes — you don't want to make the pipe walls themselves out of thermocouples, because then instead of a Seebeck generator you'd have a short-circuited battery, with the water in the pipe as the electrolyte. So you end up joining four or five dissimilar materials together along the wall of the pipe — a recipe, generally speaking, for extra vulnerability to corrosion, although you can avoid that by some ways of doing the joints.
In summary, I think Seebeck energy harvesting from plumbing is very promising, but not as a way of extending plumbing lifetimes.
https://www.youtube.com/watch?v=KZX0aTvbEzo https://www.youtube.com/watch?v=OOeBJ8mDr8Q
> 99% Invisible is about all the thought that goes into the things we don’t think about — the unnoticed architecture and design that shape our world.
My understanding is that flexible hoses were not considered durable. Line your walls with flexible hoses carrying water and your insurance company is going to flip out.
Or put another way, flexible hoses didn't meet building codes.
Times change though and PEX (a kind of flexible tubing used for plumbing) is now allowed in many (all?) states.
I was thinking of installing a couple of these a few years ago, but didn't and then forgot about them. It's a pump that gets installed near a faucet; you turn it on when you want hot water; it pulls water out of the hot pipe, sending it back into the cold pipe (where it circulates back to the water heater), until it senses that hot water has arrived, when it shuts off.
As I say, I haven't tried it, but maybe I will — seems like an elegant solution, and works with existing plumbing.
There are also recirculation pipes for lung runs of hot water piping, like hot water columns found in hotels. The return circuit doesn't need to be thick, two sizes downwards will do (for instance a DN15 pipe for a DN25 column). Both the column and the return need to be properly insulated. DHW circulation pumps are usually made of brass and come equipped with a no return valve. This layout does exactly what you describe but instead of going into the cold water pipe, it goes back into the boiler.
Turn the hot water on full while you're getting ready and the shower will run until the water turns warm and then will slow the water to a small trickle, minimizing the waste of hot water down the drain with no one in the shower.
When you're ready, step in and pull the lever to restore (instantly hot) water flow.
It would be great if there was some endpoint heater like you describe, that ran from e.g. ultracapacitors that could be trickle charged from solar.
And yeah, having just built our house, I wish I had read this article earlier and learned about using minimally sized piping! Obvious in hindsight.
Ive seen some claims that solar water heating/circulation systems are now more expensive over their lifetime than collecting the solar as electric and heating water, but I've never gone through and sanity checked that calc.
Unless the small tank was big enough for most conceivable uses - in which case, e.g. in the bathroom, it would become a large tank.
A continuous flow unit at least can do what you said in your earlier post, e.g. instantaneously heat up the cold until it starts coming through hot. That's why I was thinking the supercaps, they might provide just enough juice for those 45 seconds or whatever, and also hopefully be reliable enough for decades of use, like you would expect from a hot water appliance.
The Manifold system is a "home run" with 1/2" to all fixtures except the tub, and the Zoned system is a mix of 3/4" mains and and 1/2" branches. Since the direct run should never be longer than the branched run (right?) how can the system composed of all small pipe waste more water than the system with a mix of small and large pipe? In a cold start measurement, I'd think the Manifold would have to come out ahead for every fixture except the tub, which would be a tie. And thus I'd think that any combination of fixtures would have to come out better, rather than worse.
(I'm not saying this makes the Manifold approach better overall, just that something seems off about this numbers)
So if you have a shower while your washer is in use, you only waste that little branch of water, rather than the whole trunk (or the home run in the manifold approach). Or if you wash your hands and have a shower in the same bathroom within half an hour (for example). With the manifold approach, you lose the efficiency savings when you use the sink / washer / shower within half an hour of each other.
No, I'm just assuming that the definition of a "cold start" is that the water is allowed to cool before the next measurement is taken. The alternative (which I agree is common) is a "hot start". The author defines these terms on the box on the bottom left of Page 76 (which I don't seem to be able to copy and paste). Since the chart explicitly says "cold starts", my question/complaint is that as labelled, I can't see how the chart can be correct. I agree that measuring a blend of hot and cold starts is probably a better metric to judge the systems by.
So then you would have instant hot or cold water, instead of any mixing at all.
Here are some reasons why this is a dumb idea: * can't handle branching, * pipe networks have "welling points" where water will simply remain by gravity, and no pumping will get it out.
Has anyone tried something similar?
That is a big "if"...
This is why wells have pressure tanks, to allow the well pump to run longer cycles, building up pressure to be released over time in the tank.
There's a second issue in that pipes don't like to be empty: exposing hot and humid surfaces to free air is a bad combination.
It's just the recirculation folks are lazy AF.
Centrifugal pumps are perfectly fine with start/stop cycles and back pressure, though not with air.
When hot water is wanted, the pump pushes cooled water from the hot side into the cold side, and eventually out into the hot water heater's cold water intake. The same flow at the pump pulls hot water from the heater to the sink, and the pump shuts off and closes the connecting valve when hot water arrives at the connection.
No water lost, no re-circ except when wanted. Use the sink to set-up to bring hot water near to the shower. Locate or repeat as needed if you have multiple "cold" bathroom or kitchen locations. The reverse flow thru the cold water piping is, uhm, counter-intuitive, but appears to work.
https://www.amazon.com/Laing-LHB08100092-AutoCirc-Recirculat...