A question about tankless water heaters...

[Javaman]

Okay, I have had one in my house now for about 7 months. And the one thing that is making me concerned is the time it takes for the water from the tap to heat up.

The whole point of getting the tankless heater was to save water and energy.

However, my wife and I are finding that it is taking a long time for the water to heat up at the tap, thus wasting a lot of water.

Is there any solution to this?

[phantom power]

1. is it a point-of-use heater or central?

[Javaman]

3. Central. What is a point of use? never heard of that one. nt

[PLF]

5. I've seen units that are under the kitchen sink.

I think that is what he/she is referring to.

[phantom power]

7. point-of-use is a heater that's right under the sink. So it's instant.

If you have a central heater, it's going to take a while to get hot water for the same reason that a central tank does. the water in the pipes goes cold. When you turn on the hot water, all that cold water in the pipes has to flush out before you get the hot water.

There is still benefit to a central tankless, since you aren't spending any energy keeping a tank full of water hot when you aren't using it.

I've always figured that the ideal setup is tankless point-of-use, at every faucet. I suppose for showers too, but I don't know where you'd put it.

[kestrel91316]

11. They have tiny tankless, I think, that will fit right under the

bathroom sink and serve all that bathroom's HW needs.

[Delphinus]

14. Speaking of showers,

I traveled by train two years ago and used the shower they had on board. You pushed a button and it came out for 90 seconds or so, turned off to lather and wash, then you pushed it again to rinse off. The heat was set (hopefully) when you turned it on and stayed there when you hit it again to rinse.

Any idea where to get something like that?

[Warpy]

10. Point of use is what they use in Europe

It's generally a wall mounted unit over or under the sink in the kitchen and on the bathroom wall there. Water heats up instantly because it doesn't have a long distance to travel through the pipes from a central point in a house.

You're still saving energy but as a desert dweller, I get what you're saying about water waste. Have you considered catching the cold water and using it to wash dishes, dump into the clothes washer, water plants, or just pitch outside at shrubbery, flowers, veggies, or trees? There's no reason water has to be wasted if you just catch it and use it.

[Rosa Luxemburg]

2. water goes cold

yes it takes a long time to heat up. My parents have one of these and if you are running the water for some time it starts to go cold and then heats up again. I don't know if there is something wrong with theirs?

[PLF]

4. Do you have a pier and beam house. Are the pipes insulated?

That will help. As well, how far is the heater from the tap?

[Javaman]

9. Concrete foundation. nt

[mainer]

6. These systems are common in Europe

I think it's a trade-off: do you save energy or do you save water? It sorta depends on where in the country you live. If you're in the desert, you'd probably be better off having a heated tank and solar energy. If you live in the cloudy north, where water is abundant, then you're better off saving the energy.

[fed-up]

8. I can't answer your question, but there is a recall on Rheem

http://www.consumeraffairs.com/recalls04/2007/tankless_water.html
Rheem, Ruud, Richmond Tankless Water Heaters


February 21, 2007
Tankless water heaters sold under the Rheem, Ruud and Richmond brands are being recalled because of a carbon monoxide poisoning risk.

Components inside the water heater may shift during transit, causing an air filter door switch to operate improperly. If the switch fails and the air filter door is out of place, the water heater could continue to operate and dust and lint could build up, posing a carbon monoxide poisoning hazard.

The recall involves indoor models of the Power Vent 199,900 BTUH tankless water heaters. The brands and model numbers included in this recall are listed below and are located on the front of the unit and the rating plate. The water heaters have a cream jacket or gray jacket enclosure with the piping on the top and bottom of the unit. The rating plate is a silver label located the front of the unit, in the lower right hand corner.

models listed at link

[Kolesar]

12. use manifold distribution instead of a "tree"

I would recommend having one manifold near the hot water heater. All the lines would branch out there and you would have a direct run to each faucet. You use a "slightly smaller" hot water pipe that holds less than a gallon of water. Then you don't have to push all the cold water out of a big pipe before it gets to your tap.

The other comments about the construction of your house give me a hint that you may not be able to break into the floor and put in a pipe, though. Maybe you can run it through an air duct. Your solution may be a high-current circuit and an electrical point of use heater in the bathroom or wherever the problem is.

I think you would be having this problem even if you had a hot water tank instead of a tankless heater.

[SheilaT]

13. In 1980 on a trip to Hungary

we stayed in a private home in Budapest. There was a point-of-use water heater in the shower. I mean, in the shower. It was a gas unit and we had to fire it up to take a hot shower, and then carefully avoid bumping up against the open flame.

[kittykitty]

15. Any brand names for point of use? I have a situation that needs one-read more, please.

We built an addition to out home with a bedroom and bath for me (as I am handicapped and can't go upstairs anymore). The (standard) hot water heater is located at least 45 feet from the hot water tap in the bathroom. It takes over 60 seconds--more like 1 min 20 seconds for the first warm water to reach the tap.

Needless to say this is a pain when you want to wash your hands after using the bathroom. I usually just scoot (I use a scooter) to the kitchen to wash my hands.

It takes the same amount of time for the shower to get hot. The shower tap is about 1 foot before the sink. But that doesn't bother me as I turn the water on before I am actually ready to get in.

What I need is some little thing, not necessarily a little tank, that heats the water immediately when I turn on the water at the sink, and then turns off when the hot water from the HW heater finally reaches the bathroom tap.

[DemSigns]

16. Easisest DIY fix

http://www.lainginc.com/instant.htm

Autocircs use a little power but do the job. The down side is you have some hot water in your cold water pipes a lot of the time.


ACT-303-BTW
How The System Works:

The pump is installed under the sink or faucet farthest from the water heater -- where hot water usually takes the longest amount of time to arrive.

A built-in temperature sensor automatically turns the pump on when the water temperature in the hot water supply line cools down to 85º F. This cool water in the hot water supply line is then pumped into the cold water line and back into the water heater.

The pump turns off automatically when the hot water supply line to the faucet reaches 95º F, ensuring the instant availability of shower warm water with maximum temperature hot water only seconds behind. When the pump is automatically turned off by the built-in thermostat, an auto closure device prevents hot or cold water from mixing in either supply line.

Hot water will also be instantly available at all other faucets in the supply line between the water heater and the faucet where the pump is installed.


The Under-Sink Instant Hot Water Pump System...

* does not require a return line.
* requires only 33 watts of power.
* comes complete with a 6 ft. long power cord.
* requires only one pump and one installation for all fixtures on the hot water plumbing line.
* has built-in fixed thermostat or an optional, adjustable thermostat.
* saves the average family of four up to 17,000 gallons of water annually.
* is silent during operation.
* saves energy, money, water and pays for itself in a short period of time (see energy saving chart).
* has a built-in 24 hour timer which allows the selection of system operating periods to suit family usage.

[hunter]

17. This approach may not work, and could cause problems.

Some on-demand heaters might not kick on when the Autocirc pump is on if the flow is not high enough, and some heaters do not control the outlet temperature adequately if the temperature at the inlet fluctuates as it would using these pumps.

With some sorts of on-demand water heaters there is also the potential for the water to get too hot, which is dangerous.

Has anyone here actually tried this, or know anyone who has?

I'd be very careful.

[DemSigns]

18. Thermostatic mixing valves a must

Good point about the instantaneous water heaters. They are strange beasts and the manuals should be read thoroughly to understand their modes of operation and limitations. I don't like instantaneous water heaters very much. I think all houses should have one gas appliance, a modulating condensing boiler to supply heat to air handlers or a hydronic heating system and hot water by an indirect hot water heater or from the boiler if it is a combination heat and hot water boiler.

Thermostatic mixing valves a must in my book for all hot water heaters. Hot water should be at 140 degrees to kill bacteria and mixed down to 120 degrees or less at the water heater.

Autocircs cut out at 90 degrees.