saving water

[Wally]

I'm building a new house and want to incorporate money saving ideas into it.

First, I like the concept of natural gas tankless water heaters.

Second, I hate throwing water away waiting for the hot stuff to arrive.

So, is it possible to put in a recirculating pump from the fixture to the cold line that would be triggered by a motion sensor in the bathroom?

If a pump is not feasible, how about as small under counter electric heater that would be connected in line with the tankless unit in the basement? This unit would be on a timer and only have power during off peak electric rates.

[PeterD]

Save a Penny, waste a Pound...

How many bathrooms? A tankless heater for (each?) bathroom is an option, but the bottom line is that you'll spend substantial money on these. Is water that scarce where yuo are that it makes this necessary?

At this point, I don't see your concept as being even remotely green or eco friendly--it is more an Al Gore type solution.

[jloomis]

[Bill]

Heat rises and metal pipe takes awhile to "heat up" (thermal mass). And distance from the water heater makes it longer before you get hot water.

Then for hand washing in the bathroom sink, barely warm water should do.

For washing dishes, hot is needed to get the grease off.

For showers, warm will do, however if you have a lot of people in your house, you need to set the water heater to hot so less hot water is used for each shower (hot mixed with cold) and you have hot water left for the next person.

So...

Install a small electric tank under each bath sink and set them to barely warm. (So long as you have chlorinated city water, otherwise bacteria can grow in warm water.) Connect the water heaters to the cold water.

And bathtubs close to each other - water heater under these in basement. Use CPVC plastic pipe for hot water lines as this does not need to be heated up. Run water heater in early morning if time of use meter.

Kitchen small electric water heater under sink set to hot.

Plumb water heaters so hot water pipe does not go straight up. Doing so will be a heat loss. Route the pipe up, then down, then back up. Insulate. This traps the heat.

[ransley]

That will likely doube the Ng bill and save pennies in water usage, How long is the HW run. How many baths, people, and gpm will you use out of the shower, I have Ng tankless but you have to do alot of research to know if it right.

[Just a thought]

Does anybody have a plot of where the best efficiency is?

This is an interesting question. Suppose for a shower you have to waste 3 gallons a day to get some warm water. Suppose the water costs 3 cents. Now, how much does it also cost to heat those 3 gallons because when they left the heater they were heated.

I guess unless you have a large family it doesn't much matter.

Of course there's also the convenience factor. If I can walk in and take a shower without having to wait a minute, then I'm a happier camper.

Here's the solution, hook the toilet up to the hot water line. Now, use the toilet and those gallons will go into refilling the bowl instead of down the drain unused.

Problem solved.

[CWatters]

Interesting. Got a URL for this?

Presumably there is an indicator that tells you when the fixture is upto temperature?

[Erik Dillenkofer]

[Art]

[CWatters]

Thanks.

I'll post that on the UK Green Building forum.

[Andy Energy]

Not recommended

1. Electric water heating can be very expensive. One need to compare the $ per million BTU=92s of different fuel types
2. Small electric water heaters are normally poorly insulated.
3. Wiring may be an issue with electric water heaters depending on the size of the heating element.
4. Circulating pumps will seriously increase the operating cost of the water heater unless the total loop is heavily insulated
5. Chili pepper on demand circulating pump. I bought one and sent it back. Unless they changed it was so noisy it could be heard throughout the house when on.
6. Tankless water heater. On large usages they are fairly efficient but on small usages they are very inefficient. If you decide to get one be sure to get one that uses a pvc vent pipe as they are more efficient than the ones that use stainless vent pipe. One cannot use an on demand circulating pump. When the pump stops the burner will shut off and you may get an amount of cold water after getting into the shower (bummer). The good units are complicated and expensive to fix. Will take longer to get hot water than a conventional tank.

Recommendation

1. Install a unit such as a Phoenix, it is better than 90% efficient. They are big enough to heat your hot water and use an air handler with a coil to heat your house. You will get high efficient space and DHW heating.
2. Install an on-demand circulating pump such as a Metlund and either use the button to activate or motion sensor.
3. Use a main plumbing tree and small lines off of it, if done properly one can waste only about one cup of water before getting hot water.
4. Put a good amount of insulation on the hot line and the return loop. Once the line is primed it will stay hot (depends on the amount of insulation)

Whole House Performance

Andy