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Old 10-01-12, 01:55 AM   #1
bikin' Ed
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Default Extra H20 heater

It will soon be time to replace my gas water heater. It is a 40 gal. natural gas unit. It in in the basement almost directly under the kitchen sink. Short run low heat loss. The two baths are directly over/under one another, but it is quite a bit long run, thus higher heat loss. And the water must be run for some time to get a comforatable shower temp.

My thought is to downsize the main heater to 25 or 30 gallons, and add a five gallon heater in the hot water line just befor the baths. I'm thinking that this should give me almost instant hot water at the shower--saving water.
And when not being used, I'll only be keeping 30 or 35 gallons warm--perhaps saving energy.

The main unit will again be nat. gas, but the 5 gal. unit will need to be electric. Rate wise neither is fuel is priced out of line, though I know gas will be a bit more efficient. Both new units would be as high efficiency as I can afford.

So gurus of the btu, would it be worth the extra expense of two heaters and the extra work of replumbing and running electric. I'm pretty sure the new set up would be ecologically better, but my selfish desire is to save money in the long run . So what you??

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Old 10-01-12, 08:19 AM   #2
Ryland
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I had the same problem of waiting a long time for hot water in my up stairs, I fixed it by running new hot water pipe using PEX pipe, 1/2" PEX has a high enough flow rate for the bath tub but the pipe it's self is smaller inside the 1/2" copper, part of the increased flow rate is because it doesn't have any elbows, burs, or any other restrictions, it's a single straight smooth run, the PEX is also less conductive so it pulls heat out of the water much slower so hot water in the pipe stays hot longer!
When I replaced my hot water lines I was also able to run the water lines in a more direct route, going from over 80 feet of 3/4" iron pipe to 25 feet of 1/2" PEX, cutting the wait for hot water down from over a minute (over 3 gallons of water) to less then 20 seconds.

At my brothers house we just installed a 29 gallon Richmond water heater a Richmond/Rheem XR90, it's power vented (needs class b double wall 3" steel chimney to vent out a wall) but it was the only water heater we could find that had an energy factor of .7 and yet it can reheat water very quickly of 60 gallons per hour, it is being marketed as a replacement for a standard 50 gallon water heater, they claim that it can replace a 90 gallon water heater.

If you can't fix your water issue with better plumbing then a small 2.5 gallon point of use water heater sounds like a great idea, there are plenty to choose from that only require 120v 12amps to run, so you can plug them in to a regular outlet that doesn't have any other high loads on it and by the time you've used up the hot water in the small tank it should be getting more hot water to make it up.
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Old 10-01-12, 09:14 AM   #3
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I love the idea and plan on doing something similar myself with my upstairs bath once I get a gas boiler setup in the basement. Right now I'm using a Steibel Eltron on demand hot water heater. The price didn't break the bank, but paying for it a few gallons at time would take a very long time to pay for itself. I'd suggest the replumbing that Ryland suggests first. PEX is pretty cheap and its easy to run.
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Old 10-01-12, 05:40 PM   #4
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Quote:
Originally Posted by bikin' Ed View Post
It will soon be time to replace my gas water heater. It is a 40 gal. natural gas unit. It in in the basement almost directly under the kitchen sink. Short run low heat loss. The two baths are directly over/under one another, but it is quite a bit long run, thus higher heat loss. And the water must be run for some time to get a comforatable shower temp.

My thought is to downsize the main heater to 25 or 30 gallons, and add a five gallon heater in the hot water line just befor the baths. I'm thinking that this should give me almost instant hot water at the shower--saving water.
And when not being used, I'll only be keeping 30 or 35 gallons warm--perhaps saving energy.

The main unit will again be nat. gas, but the 5 gal. unit will need to be electric. Rate wise neither is fuel is priced out of line, though I know gas will be a bit more efficient. Both new units would be as high efficiency as I can afford.

So gurus of the btu, would it be worth the extra expense of two heaters and the extra work of replumbing and running electric. I'm pretty sure the new set up would be ecologically better, but my selfish desire is to save money in the long run . So what you??
I was thinking about the same setup. Small electric WH can fit under sink. I don't think you should downsize your main WH unless you feel like it is already too big for your needs. Also you should set thermostat in your electric unit lower then your main unit. In this case it will serve only as small storage and not HWT. As soon as you open your tap you will get hot water right away and soon slightly warmer water will come and replace water in your electric unit so it will just keep it warm. It might take some time to adjust 2 units to run efficient.
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Old 10-01-12, 07:23 PM   #5
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I have a Bradford-White 2 gallon electric water heater under the kitchen sink. We get hot water almost instantly - 2 or 3 seconds and it's hot.

It works superbly for the many small hot water draws of a kitchen faucet, but I don't think it would work so well in a shower. The temperature fluctuates from hot to plenty warm back to hot as the cold water in the line mixes with the hot water in the tank.

I vote for the 1/2" PEX that Ryland recommended.

Plumbers like to run a main hot water line about 3/4" diameter, then branch off that. Hot water supply is more efficient if you run each line straight from the water heater, and size each line for the flow of that particular application.

I once ran a 3/8" copper line to a kitchen faucet. That worked very well, with only one pint of cold water before the hot water arrived.
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Old 10-01-12, 07:39 PM   #6
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Quote:
Originally Posted by JRMichler View Post
I have a Bradford-White 2 gallon electric water heater under the kitchen sink. We get hot water almost instantly - 2 or 3 seconds and it's hot.

It works superbly for the many small hot water draws of a kitchen faucet, but I don't think it would work so well in a shower. The temperature fluctuates from hot to plenty warm back to hot as the cold water in the line mixes with the hot water in the tank.

I vote for the 1/2" PEX that Ryland recommended.

Plumbers like to run a main hot water line about 3/4" diameter, then branch off that. Hot water supply is more efficient if you run each line straight from the water heater, and size each line for the flow of that particular application.

I once ran a 3/8" copper line to a kitchen faucet. That worked very well, with only one pint of cold water before the hot water arrived.
With pex price it is more efficient to have manifold somewhere close to HWT and 1/2 pex from manifold directly to facet. The problem is when your plumbing is already there.... 5 gal water heater might be the answer. 2 gal is a really tiny unit.

I made 3/4 pex mistake in my house and it takes forever to get hot water in some places.
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Old 10-02-12, 02:47 AM   #7
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Bikin Ed
Had you consisdered a small circ. pump under the sink instead of operating another thirsty heating element?? This can be wired into your bathroom light so you won' foget to shut it off. The down side is a return run down to your tank supply side. The return line must also have a check valve but some circ. pumps are supplied with one internally. This system may also work for a demand type hot water heater. As the circ pump is turned on the flame starts and within seconds hot water where you need it.

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Old 10-02-12, 11:21 AM   #8
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A pump on a motion sensor would do the job day or night.

1/2" pex should be able to supply enough water because it's not common to have someone showering and someone running a sink of hot water at the same time in the same bath room, altho if you want to run the same line to both bath rooms 3/4" might be a better choice at more then twice the volume of 1/2"
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Old 10-03-12, 07:55 PM   #9
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My 2 gallon hot water heater is in the hot water line. It only needs to deal with the 2 or 3 quarts of cold water between the hot water heater and the kitchen faucet.
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Old 10-18-12, 08:55 AM   #10
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Have you decided what you're going to do bikin' Ed?

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