Pre-heating shower / sink water
 

One of the things I hate the most is waiting for the hot water to come through my piping for showers or even washing dishes, etc ...

I know to address this type of concern tankless heaters were invented which deliver nearly instant hot water at any outlet installed near it, but even that solution is expensive when multiplied by water outlet sources ..

Therefore I thought of something else for new home or remodeled home designs. Why not run the hot water lines through the attic to the sources? This is almost ideal for those of us living in places like florida where attic temperatures stay well above 100 degrees year round.

By doing this the water in the pipes is already hot the instant you turn the water on. The only draw back is excessive heat when you open the hot water tap. In fact the ambient temperature of the pipes will likely force you to use less hot water altogether making this a win win. Enclose your water heater with a compartment open to the attic and now you have even better heat insulation for your heater, making it work less too.

As a by product we should be saving water as well not having to wait for the hot water to pour out ..

Am i missing something here?

You could do that. You still have the pipe in the wall that will be room temperature that you'll have to run out of the faucet before you get the hot attic water though. Also, you'll have to wait that much longer to get the actual hot water from your water heater.

You are right about having to wait for the water out of the tank, but the water in the line will be heated by the ambient air temp in the attic, as far as the water in the wall, its only three feet or less embedded in Sheet rock, that water should also get heated by the water in the rest of the pipe resting in the attic I figure.

I may attempt this at my mother's house, she is getting ready to remodel the house and our bullet list is;

Solar Attic Fans
Solar Water heater system
Changing the 22 year old windows for newer energy efficient ones
Changing light bulbs out for CFL or LED depending on avail
Tearing up old stained carpet and replacing it with Cork board flooring
Updating a/c air exchanger
Adding zone a/c system to home
*Modify plumbing through attic to utilize existing heat source
*Encase water heater tank in a room open to attic to use heat as additional insulation.

This is not happeneing all at once. In fact one project at a time and watch the results, its exciting and then motivating to continue to drive down your energy costs, kinda like Hypermiling ..lol

I'll start a thread once we start the first project, gathering 3 months of current energy usage as a baseline.

Remember to protect against freezing. Running a line through the attic sounds good until it bursts on the one night a year that might be cold enough to do so... Perhaps in the "winter" you will have to throw on some tube insulation that can be taken off when temps warm up. Similarly, you may want to have the option of closing off the attic from the water heater. Here in Alabama, lots of people have their entire water heating systems in the attic, and lots of people have their lines freeze on cold nights. One guy I work with had his tank burst when he was at his parents house for Christmas-New Years... He had shut off the water to the house, and shut off the gas. This meant the water heater cooled, then froze, but didn't flood his house, or in this case, garage (since his was in the attic over his garage).

Wise advice, however in the 39 years that I have been in S. Florida temperatures have NEVER dipped cold enough to freeze anything. However making sure the piping lies underneath the existing insulation would be a wise move ..

Thanks ...

It pays when building a house to install the HWC centrally to the serviced outlets or closest to the areas of highest usage, eg bathroom, laundry. In out house however the distance to the kitchen is a 20 meters pipe run, with unacceptable delay and hot water wastage. I installed a smaller water heater directly under the floor below the kitchen sink, now the delay is 1 second, so it must pay for itself over time. Another solution would be use install instantaneous heaters, so initially they supply the hot water then turn off as the heated water arrives from the main HWC.

Mike

Is using smaller diameter pipes for hot water an option? That way there is less water to pour through the faucet before the hot water makes its way there. Old houses sometimes had large diameter pipes b/c the pressure in the city's water system was low, today you could get away with smaller pipes.

I imagine you could do that. You will loose some water pressure going to a smaller diameter pipe, but I have no idea how much.

There are small on-demand electric hot water heaters that are designed to fit inside a bathroom sink cabinet, that might preheat the water, but most of them are flow-limiting - meaning they limit the flow to ensure proper heat. What you want is one that just heats to the best of its ability without impeding water flow. I suspect that the solution would involve spending more money on an on-demand tank less heater, or on a hot water tank, that would make the electric shower head obsolete.

I'm planing on installing some 1/2" PEX pipe and I've noticed the ID isn't
too small, but when you look at the fittings, the ID of most of those is small!

Anyways, one thing I did to help fight the hotwater delay is to insulate the hotwater runs.
It helps the hot water get there a little faster, when it's been used lately
and is still holding some heat.

Anyways, I think using PEX will help out with HW delays, since it's not as heat conductive as copper.

I just was talking to a guy at work the other day about this. He said his dad recently plumbed in a faucet with a ~40ft run from the water heater. He ended up using 1/4" copper to get the hot water there, and the speed with which you get hot water was obsurdly fast he said. You can't run too much off 1/4" copper, but even 3/8" would be good for a bathroom I bet.

Seconded! I insulated the hot water pipes in our home (which run through the crawl space) and they made a significant difference* in time to hot water at the faucet. Even the first thing in the morning hot water arrives at the tap much more quickly than before. I suspect this would be the simplest and cheapest way to fix this problem.

* Unfortunately I didn't measure the difference, but it was very noticeable.

FWIW,
Tim

Another option is an on-demand hot water circulator. Not as cheap as pipe insulation, but depending on the system you get and the piping of your home it may be possible to install a single pump to cover the whole house. We had the same problem with waiting for hot water. We went with a circulation system that had both scheduling and on-demand capabilities. So, if we wanted hot water late at night, we just pushed a doorbell button activating the system for one run then stop. For two other baths on the same hot water main we used wireless buttons to activate the system.

We also "use to worry" about pipes freezing here as well. We read about how this unit could be used to protect pipes from freezing by lowering red temperature dial and set the timer to run once time every 30 minutes. We've survived to winters now without leaving the heat on when we're both at work which dropped our gas bill a little. We knew it was working for the fact that the water coming out the taps always seemed to be around 60F when opened and not icy cold like expected.

I live in North Florida and we regularly get "hard freezes" here, so I don't think running the pipes in the attic would be good in this area. Attic temps do not stay above 100 degrees F year round.

If you have copper pipe, changing to CPVC will help as it has about 2000X less thermal conductivity. It's much better than just insulating copper pipe. Of course, if you're trying to capture heat from the attic, you should probably run copper up there as the CPVC won't do you much good (CPVC should work if given a long time to heat-soak, but you won't get much while the water is flowing).

Also, changing to smaller pipes as has been mentioned will help because you will have less water to displace. A 3/4" CPVC pipe has 1.75 times the area (and therefore 1.75 times the volume for the same length run) as a 1/2" CPVC pipe. I think it makes sense to run the larger pipe for the main lines to reduce pressure loss, and the smaller pipe for the branches (where the flow needed will be lower) to reduce the volume in the pipe. CPVC is also cheap and easy to work with.

If you're going to be redoing the whole system, look at how you can run the pipes to reduce the overall length of the runs. This will help to reduce volume also.

Some people run a separate line from a manifold at the water heater to each faucet, allowing a smaller pipe (it doesn't have to provide as much flow as a line that feeds multiple faucets) and therefore faster time for hot water to arrive.

1/4" copper is not recommended for flows above 1 gpm, and 3/8" copper is not recommended for flows above 2 gpm. http://www.copper.org/publications/p...e_handbook.pdf

We had installed a 3/4 hot water supply line to the far end of the house and 1/2" return to the cold water supply at the hot water tank. The little trick was the check valve at the far end on the 1/2" return line to the HWT. Being the HWT was on the lower floor the gravity would circulate the hot water to the end keeping it hot there for showers etc. The check valve must be one with a light weight nylon ball with no spring so just the force of the hotter water would lift the ball and circulate the cooler water to the HWT. Both tubes should be insulated to save energy and it worked well.

Randen

Is is ECOnomical?
 

IMHO, any scheme to pre-heat the hot water in the line, for instant access,
is going to have a considerable heating cost (per year). Even with good insulation on PEX pipes.

I would recommend doing the math, before going after this problem.

Most times, when I'm washing up or washing something in the sink,
I don't just stand there and let the lukewarm water run down the drain. It gets used.

It might not be convenient, to wait for the water a couple times a day, but it's
going to more economical in most cases.

I think that 1/2" PEX with insulation over it, is about as far as I'm willing to go.. :D

Better yet: if you have to pour some cold water before the hot arrives, you can start to rinse something and/or catch that water for flushing.

Circulation is the way to go - if you have the possibility of make a return pipe, or a full circuit. For a bathroom, all you have to do is connect a timer to the light switch, and then to a small pump.

Whenever the light is turned on, the pump runs for a set amount of seconds, depending on the pipe length. This way, you don't need scheduling, which doesn't work anyway when you sleep late, wake up in the middle of the night and so on.

From you turn on the light until you use the hot water, there is usually at least a minute or more, whether you use the toilet, shower or what. And if the light stays on, the pump stops. The timer is only activated when the light goes from on to off, and then only for a set period of time.

Other places where use of water is not always related to a light switch, a separate switch could activate the pump. Of course you would have to press the switch and wait before you use the water.

I fitted both of our bathrooms, which are a 40' pipe run from the water heater with switched circulation pumps. What I did was to place a pump and electric valve between the hot and cold pipes. A temperature switch on the hot pipe. To make the water hot, you push a button to latch a relay that opens the control valve and starts the pump, as well as turns on a little red light. When the hot water pipe reaches 100 degrees, the temp switch unlatches the relay, shuts the whole mess off and you have hot water. I also have one under the kitchen sink, because the way the house is plumbed the hot water has to go to the north end of the house and back to get there, approx. 60'.

The electric valve in line is to stop thermosiphoning on a continuing basis. The system was made from available items and not too costly to implement.

mike