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Old 06-16-11, 03:34 PM   #11
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Originally Posted by Piwoslaw View Post
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 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.

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Old 06-16-11, 05:40 PM   #12
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Originally Posted by Xringer View Post
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.
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.

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Old 11-12-11, 04:01 AM   #13
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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.
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Old 11-12-11, 10:00 AM   #14
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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.

Last edited by Patrick; 11-12-11 at 11:57 AM.. Reason: typos and added info
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Old 11-13-11, 09:56 PM   #15
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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.

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Old 11-14-11, 10:48 AM   #16
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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..
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Old 11-14-11, 11:04 AM   #17
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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.
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Old 01-12-12, 09:02 AM   #18
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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.
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Old 01-12-12, 09:48 AM   #19
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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.


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