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Old 02-09-2011, 11:30 AM   #1
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Tank to Tank-less Hot Water


I want to replace my standard gas hot water heater with a gas tank-less one. What all is involved?
Thanks Mike

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Old 02-09-2011, 12:49 PM   #2
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Tank to Tank-less Hot Water


Not to be a smart a** but if you have to ask you best just call in a plumber.
Key things I'd say: why do you want to switch? Cost difference + install costs can be high.
Is your gas supply adequately sized? Can you vent it easily? Are you doing the work?

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Old 02-09-2011, 01:07 PM   #3
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LOL if you have to claim not to be a Smart a** must be one. No worry so am I.
I will ask a plumber for advice, just thought I could get some input. I will do the work myself. I have a 1" gas line to my hot water heater area. I'm not sure of what size exhaust is necessary. It's a straight shot up through the roof. I want to change to gain the space taken up by the conventional hot water heater.
I have installed many conventional hot water heaters.
Thanks Mike
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Old 02-09-2011, 01:14 PM   #4
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Tank to Tank-less Hot Water


Well as you mentioned in the response the smart**s......, you are aware the gas service may need upsizing.

I am sure your furnace is gas as well and depending on what size your furnace is, HW heater, and if you have any other gas appliances, 1" feed may not be big enough.

You may want to look for a condensing tank-less unit, that way you could mount and vent out any side wall with PVC.

If not condensing I believe the vent size is 4" for most units.

Personally, I looked into doing this a couple years back and decided not to, if you read all the reviews from all the manufacturers, you will find a common thread through all the complaints. The most common complaint was the gap in hot water, when there is a mimimum flow condition, as when brushing your teeth, rinsing dishes, etc, the burner shuts down and then has to go through its startup cycle, leaving a slug of cold water.

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Old 02-09-2011, 01:27 PM   #5
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Tank to Tank-less Hot Water


My furnace and hot water heater are located in the center of the house side by side. To enlarge the exhaust to 4" shouldn't be a problem. The 1" gas line is reduced and does feed both the furnace and hot water heater. I can tee of the main line coming in the house and run another line through the attic if necessary.
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Old 02-09-2011, 01:32 PM   #6
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My furnace and hot water heater are located in the center of the house side by side. To enlarge the exhaust to 4" shouldn't be a problem. The 1" gas line is reduced and does feed both the furnace and hot water heater. I can tee of the main line coming in the house and run another line through the attic if necessary.
Thanks Mike
The 1" feeds your current furnace and HW tank, a tankless unit fires at a much higher BTU/hr rate than a standard HW tank, needing a 3/4" line just for the water heater. You may need a 1-1/4" line coming into the house for both.

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Old 02-09-2011, 01:40 PM   #7
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Mark, Thanks. If I enlarged the gas line and change the exhaust to 4" then that would cover the basics, right?
Mike
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Old 02-09-2011, 01:45 PM   #8
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Mark, Thanks. If I enlarged the gas line and change the exhaust to 4" then that would cover the basics, right?
Mike
Yes other than running the cold and hot lines over the the heater location.

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Old 02-09-2011, 01:51 PM   #9
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Tank to Tank-less Hot Water


i looked into this as well when replacing my hot water heater recently. there were a couple issues, one of which was the gas line supply not being large enough with the large increase in BTU's needed. another was the need for an electrical outlet since all the new units use electric fan powered exhaust. the drain setup was weird too, wasn't sure if i could use the existing drain or not. needing to at least increase the gas line size and add an electrical circuit were additional costs that weren't worth it, considering the savings on those units really isn't all that much when you consider the cost.

sure would have been nice though. dealing with a 50 gallon water heater in an attic in a 2-story house is a real b*tch, not to mention what happens when the tank fails, the drain can't keep up and it starts leaking through the ceiling.
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Old 02-09-2011, 02:21 PM   #10
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I have power in the closet since my furnace is there also. 15 years ago while on vacation the hot water tank failed. What a frigging mess that was. Now the hot water heater is 15 years old. I want the extra space so I can move a wall 12".
I'm old, retired, and damn the cost. I'm getting one.
Mike
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Old 02-09-2011, 02:30 PM   #11
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I have power in the closet since my furnace is there also. 15 years ago while on vacation the hot water tank failed. What a frigging mess that was. Now the hot water heater is 15 years old. I want the extra space so I can move a wall 12".
I'm old, retired, and damn the cost. I'm getting one.
Mike
yes, i have power in my attic for my furnace as well. however, someone can correct me if i'm mistaken, but i'm pretty sure the furnace is supposed to have its own dedicated circuit.
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Old 02-09-2011, 02:35 PM   #12
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Tank to Tank-less Hot Water


Really, Thanks. Now I know why I joined this forum, I'm learning all the things I didn't think about. Maybe I'll have to run power to the tankless heater.
Mike
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Old 02-09-2011, 03:51 PM   #13
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Tank to Tank-less Hot Water


I put in a dedicated circuit for my Takagi tankless water heater and I made it GFCI. GFCI was probably not required but anytime you mix water and electricity in the same area I would like the additional protection.

On tankless heater.........just be sure to get the right size in btu's, flow rate and recovery rate. Too small a heater and you will be sadly disappointed. I sized mine for 2 showers, washer and dishwasher all at same time and have never run out of hot water. Mine has been in for 9 years and have never had any problems.

I ran 3/4" gas piping to my heater and it works fine. I have a unique situation in that I have high pressure gas to my house and then regulators on each appliance. The reason for the high pressure gas service is to get enough flow to a pool heater about 80 feet from my gas meter. They refer to my gas service as PSI service versus OSI (ounces).

Most important item.........size the heater correctly.
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Old 02-09-2011, 04:58 PM   #14
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Tank to Tank-less Hot Water


When I contemplated nat gas tankless 1.5yrs ago the deal breaker for me was that you are not supposed to use your existing chimney. So the exhaust needs to go out the side of the house, and also the exhaust venting tubes needed to be stainless if I recall correct to handle higher temps than most people's existing venting. Installing the tankless and minor plumbing/electric for me is a lot of work - I didn't want to deal with new venting and putting holes in the side of my house too. I do know people who installed tankless using their existing chimneys but all I read informed me that was not advisable.
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Old 02-09-2011, 05:27 PM   #15
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MRDIPPY and all that responded to my post. I thank you. I'm starting to understand what bob22 meant on his reply. This maybe just something I'll have to reconsider.
Thanks Mike

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