Pre Warm city water before water heater

Old 01-11-14, 12:20 PM
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Pre Warm city water before water heater

As I prepare to renovate my daughter's bathroom, I am wondering if and how to pre warm the city water supply in to the hot water heater.

This time of year, in the Great White North, the city water is ice cold.
The tank works harder and her hydro bill shows it. She has hair to her hips, so every shower is a mega shower, even with the lowest volume shower head on the market installed.

There is no chance for me to install the recover units like these at this time.

Power-Pipe | Power-Pipe R3-30 Drain Water Heat Recovery Unit | Home Depot Canada

Would a 30 foot pipe warmer, the type to prevent freezing, even make a difference in the flow temperature?

If I installed a coil of 100 feet of PEX, the contents of the PEX is only about 1.5 gallons, would it even make a dent in the ice cold water entering the heater?
Old 01-11-14, 12:39 PM
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Sounds like you do not have enough capacity or too low a recovery rate.
Maybe a larger different cold water heater or another in series or parallel.

You have cold water coming in and you want to to a specific temperature level and a longer feed line would just use the heat in your home for miniscule rise in supply temperature.

Old 01-11-14, 12:40 PM
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You don't get something for nothing. However you warm the water there is a price to be paid. If you warm it in the air inside the home it is acting like an air conditioner so the furnace must run more to provide the heat. You can heat the water directly and avoid "the middle man". No matter what you do heating water requires energy and the water heater, the appliance specially constructed to heat water, is probably the best way to do it.

What is the summer temperature of the municipal water? I'm betting it's probably somewhere in the 50's f (12c) and in winter may be 35-40f (2-5c). When warming water to 140f (60c) the difference between summer and winter water temperature is a small percentage. Adding 10c to the incoming water temp, while helpful, is a small step when trying to get it up to 60c. If you want more hot water capacity I would go a more traditional route with a tankless water heater, larger tank heater or a hair cut.
Old 01-11-14, 02:21 PM
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Just running the physics in my head, it would seem to me that you either pay Peter or you pay Paul. You heat it here or you heat it there. I can't see the problem being where the water gets heated. I would think the real problem is the difference between the temperature of the water coming in and what temperature you want it to be, going out.

That being said, I have seen the odd gismo that tends to warp the rigid laws of physics before so maybe some others have some more experienced answers.

The only other thing that might help, if she isn't already using one, is one of those shower heads that reduce the amount of water used without a noticeable difference to the user. Another one of those warpages in the laws of physics.
Old 01-11-14, 06:05 PM
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This time of year, in the Great White North, the city water is ice cold.
The tank works harder and her hydro bill shows it.
As long as the water service doesn't freeze, the temperature of the water is really no different down here in the states. The only difference I can see is I don't have a hydro bill, just gas and electric bills. Maybe she just needs a bigger water heater.
Old 01-11-14, 08:25 PM
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Thanks guys,
I guess this is more about me over working things (so I can have a reason to tinker more ).
She does not complain about lack of water but I really do not want to give her more capacity either. I walk by the cold water entry pipe and stop and wonder......

Pilot Dane
.....larger tank heater or a hair cut.
Tempting! But I may like her long hair even more that she does.

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