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Hot water recirc. system(15 posts)

Hot water recirc. systemjtolleson
Aug 29, 2003 9:38 AM
OK, not only is this non-cycling, it isn't even politics! But where else are there so many folks whose opinion I respect? Ahem.

We're building a house. The water heater(s) will be in the basement, master bedroom on the second story. I don't want to leave the tap running for 3-4 minutes waiting to suck hot water up two stories.

Our builder mentioned a recirculating hot water system. I guess it continually cycles hot water upstairs and then back to the water heater, etc. More instantaneous hot water response. But does it work well? Is it reasonably energy efficient? Does it make noise?

Anyone in the know about these gadgets?
re: Hot water recirc. systemPdxMark
Aug 29, 2003 9:52 AM
I looked into these a little bit. They are common in parts of California where water resources are limited.

Between traditional water heaters and recirculating systems, it seems that the choice is between wasting energy and wasting water. This might be out of date, but a recirculating hot water system will expend energy keeping the water hot all the time. It could be argued that filling the pipes full of hot water each time you use them also wastes energy. But typically, that happens once a day or so (for an upstairs bedroom). So for an upstairs master bath, it seems like the wasted energy in a recirculating system would outweigh the water savings, unless water is scarce and expensive.

I haven't looked into them , but I always thought an upstairs "flash" heater would be good, depending on their energy efficiency. No wasted energy from recirculating hot water all day every day, no wasted water to fill pipes from the basement with hot water. Open the tap and out comes water heated right there near your bathroom.

Does anyone know about these flash heaters?
re: Hot water recirc. systemClydeTri
Aug 29, 2003 9:53 AM
common engineering sense would tell you that you will have heat loss from the pipes, which you will pay for directly and indirectly. You pay for it directly in reheating the water and indirectly in cooling your house from the heat loss during seasons when you use your a/c. On the flip side, during the winter that heat loss will help heat your house. Seems like a nice to have thing with some cost ensued. Seems to be "non-conservationist" though...

Now, they do make some on demand hot water heaters you could use on the second floor. They only heat the water when you need it at that location. Cost? no idea..
Advertised prices I've seen for on-demand water heatersThe Walrus
Aug 29, 2003 10:14 AM
start at about $1500, but I'm sure there are better deals to be had. These are very common in Europe, and they're the nearly universal choice in Japan, so the bugs have definitely been worked out.
I'm willing to payjtolleson
Aug 29, 2003 10:17 AM
within reason, a substantial upcharge from a standard plumbing set up. I mean, with the size of our construction budget, adding an extra $2k (or whatever) to do the right thing (and get prompt hot water) would definitely be worth it.

Maybe I should go to a good plumbing supply place.
On demand heatersjtolleson
Aug 29, 2003 10:14 AM
Yes, there are such a thing and I guess I need to know about those, too. They are a variation on the "tankless" water heater (I think) and my main question is about capacity. I don't really understand "tankless" hot water I guess because I don't see how it can heat fast enough not to run out for, say, a longer shower.

An internet research re: "on demand hot water" seems to suggest EITHER a recirc. system or these "tankless" gizmos. Despite the appearance of waste, in dry climates a lot of cities are apparently giving credits for installation, assuming that the water savings outweighs the additional energy. Denver is becoming one of those water-sensitive communities sooooo... and then I saw a recirc. system supplemented with a solar panel which gave the "green" side of me warm fuzzies.

Waaaahhhh I'm overwhelmed.
The tankless units that I've seenThe Walrus
Aug 29, 2003 10:37 AM
pass the water in a coiled pipe which is suspended over the burner; the water actually makes several passes over the heating unit, so that each time around, it gets hotter. The performance is very impressive.
tankless designs work fine, for a task at a time.dr hoo
Aug 29, 2003 11:24 AM
They will give you plenty of hot water for a shower, and should keep it hot for 24/7 if you want to shower that long! The knock against them is that they can't handle multiple tasks well. So two showers is out, or a shower and the washer at the same time. There are ones with larger capacity, but that's the general drawback. That and a higher initial price (with lower operating costs).
tankless designs work fine, for a task at a time.PdxMark
Aug 29, 2003 11:49 AM
So an on-demand heater could serve a master bath well, if there was a traditional heater serving the rest of the house?
it should. no reason why it wouldn't.dr hoo
Aug 29, 2003 2:59 PM
It might also lower the installation cost (slightly) compared with a conventional heater elsewhere, given you only need to run cold water to the room.
re: Hot water recirc. systemmohair_chair
Aug 29, 2003 10:20 AM
My parents have one. Being thrifty folks, they run it on a timer, so it's not circulating water all day, just around the times they usually need it. Since they are both retired, their days tend to be fairly predictable! Dad being a former electrical engineer, also installed an override for the timer, so on unpredictable days, he can turn it on a few minutes before jumping in the shower. It works out very well for them.

One problem I've heard about is that supposedly these things can wear away your pipes. It's unproven, just a theory, but the theory is that if you have water with high mineral content, constantly circulating water is kind of like sandblasting. Eventually pinhole leaks develop and you have a mess. If you get one, ask your builder to use Type L pipe (outdoor rated, thicker) not Type M, and consider the timer idea. Do a search on 'copper pinhole' and see what you find.
Just insulate the pipes.Live Steam
Aug 29, 2003 12:08 PM
Well it actually depends upon where the HW heater is placed in relation to your bath. Obviously it is impossible to stack all the water service requirements or to cluster them in a sprawling house, but you should look to strategically place it somewhere in the basement that limits the longest run to any one tap. Simple pipe insulation should help greatly. The circulator is used in very large homes, in hotels and other large structures where proximity to the source is relatively far away. The circulator will keep your electric meter spinning nicely :O) Rimmer
Aug 29, 2003 2:15 PM
I was in the plumbing business for 18 years, and am now a building/plumbing inspector. The tankless H2O heaters of the past just did not meet the demands of American household needs. The link posted above is the website for Rinnai hot water systems, I went to a seminar on them and I was impressed. If I was building a new home this is the system I would use for hot water and home heating. The initial cost seems a little high, but if you crunch the numbers on a properly installed system by a reputable dealer, I think the payback is there.
re: Hot water recirc. systemrwbadley
Aug 29, 2003 9:32 PM
I would recommend the small (two gallon type) tankless. These are only a few hundred bucks. Hooks in series with the main hot, you will have water instantly, and the make-up hot water will allow for nearly unlimited volume.
cheap, feel good solution?DougSloan
Sep 2, 2003 3:37 PM
Run the water first into a bucket until it gets hot. Use the water for houseplants. No energy, water, or money wasted.

Alternatively, install a source or mini water heater in the bathroom, if it can be fed from a hot water line (some, at least, require cold inlet). Then, it will provide hot water at first (just for a quick start), then you'll feed from the main water heater for the remaining needs. You could then buy a smaller or lower BTU unit than you might otherwise need.