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Old 01-14-2010, 04:50 PM   #1
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DIY gas tankless water heater


This would be in California.

I am looking to replace an existing gas water heater with a tankless gas water heater. The job to me seems pretty simple/straight forward, reroute existing water and gas lines a few feet to new heater on wall and install a new vent through the roof. Unfortunately I have called almost every single plumber in town to get estimates on the job and they either won't return my calls or do not deal with tankless water heaters. So, rather than hiring someone who won't even return my calls or someone who has less experience with this stuff than I do I was considering just turning this into a DIY job.

The water lines are no problem for me, it is the gas line work that I'm a little hesitant about. I prefer not to do my own gas lines, though I have done a few here and there and am perfectly fine connecting my own appliances. The big question is, assuming I get all the proper permits to begin with, is there any legal reason why I cannot do my own gas line in my own home? Should an inspector come by am I going to get slapped with some stupid fine for not hiring a bonefied, state licensed plumber? Or will I be screwed sometime in the future should I sell my home?

I worry about this because this is a major appliance, the other work I have done with gas lines has just mostly been either a short extension or an elbow here and there to change the direction of the line. Basically nothing anyone would ever notice, but this will be blatantly obvious.

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Old 01-14-2010, 05:16 PM   #2
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When I was working as a superintendent down in Fresno, a few years back, I did the wiring of all of our Rinnai tankless water heater units for the track. It was stupid, the electrical contractor didn't want to hook it up because it was plumbing and the plumbing contractor didn't want to hook it up because it was electrical. So it always fell on us to do it.

Anyways, it is pretty straight forward, if you have no problems rerouting the water lines, can install the correct exhaust through the roof, and can either hire someone to move the gas lines or do it yourself, I would say tackle it yourself.

A couple of things to consider are:

1. Is your main gas service big enough to handle the demand of all your gas appliances with adding the tankless system (most tankless systems demand ~200,000 BTU's).

2. The gas supply line to the actual tankless unit is 3/4" (at least for the Rinnai units, need to check the manufacturer specs on the one you purchase, to be sure).

3. It also requires an electrical outlet to power the unit.

4. The control board for the Rinnai's was pretty straight forward as long as one can follow a wiring schematic (it was pretty basic for the Rinnai's) and if you have trouble with this you can always upload the schematic here and have some of the experts help when you get to that point.

In my opinion if all of these questions you have answers to and feel confident in your skills, I would not hesitate if I were you to do some research here and at the store, and figure out how to DIY.

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Old 01-14-2010, 05:59 PM   #3
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DIY gas tankless water heater


Thanks for the tips.

I think I've got them all covered, I went back to the original blue prints of the home and using all worst case scenarios(longest runs in the plans) for the gas line I should have 9K BTU's extra after I put in the water heater. That, is of course, the worst case scenario which involves me putting a Y on the 3/4" pipe running to the furnace. If I find either a 3/4" or a 1" gas line in the walls next to the existing water heater then even better.

The electrical is no problem at all for me and I was already planning on branching off an existing lighly used circuit or just running a whole new circuit for the heater.
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Old 01-14-2010, 06:12 PM   #4
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Originally Posted by lofar View Post
I am looking to replace an existing gas water heater
How old?
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Old 01-14-2010, 06:39 PM   #5
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How old?
Its about 8 or 9 years old. For me it's not so much about the water heater/cost benefit but about the space I can recover by removing the huge tank.
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Old 01-14-2010, 07:08 PM   #6
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I don't sell, install or service water heaters, but I inspect them, and have gas fired tankless water heaters at my home, my office and at 3 of our rentals. They can work well, but we encountered a number of issues when installing them, mostly related to installers' limited familiarity with tankless heaters' special requirements. Iíve put up this page describing some of the installation issues we encountered, and how to resolve them:

Tankless Water Heater Installation FAQ - Paragon Home Inspections Evanston / Chicago / Skokie / Wilmette / Morton Grove / Glenview / Northbrook / Illinois
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Home Inspections, Infrared (Thermal Imaging) Leak Identification and Inspection Services, Roof, Attic, Building, Basement and Foundation Moisture Intrusion and Water Leak Inspections, Troubled Building Consultations - Serving Chicago and Suburbs http://paragoninspects.com/
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Old 01-14-2010, 08:36 PM   #7
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I have a tankless LP heater. It took a 5/8 supply line, but that's probably because it was LP and not natural gas.

It took a double wall vent, so that had to be replaced.

The warranty was voided for a DIY installation. You had to supply the installer's license # to validate the warranty.

We're now only using the tankless for the bathroom and it's fine for that. Previously we used it for the kitchen too, and that was horrible. They cycle on and off as you turn the water on and off, which means your hot water pipes are continuously giving you blasts of ice cold water as you try to do dishes, unless you just let the hot run the whole time.

Also, I think the one we got (250,000 btu burner) ends up using more gas than the old tank heater.

But the floorplan didn't work with the tank, so it's probably worth it.
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Old 01-14-2010, 11:15 PM   #8
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Originally Posted by pyper View Post
I have a tankless LP heater. It took a 5/8 supply line, but that's probably because it was LP and not natural gas.

It took a double wall vent, so that had to be replaced.

The warranty was voided for a DIY installation. You had to supply the installer's license # to validate the warranty.

We're now only using the tankless for the bathroom and it's fine for that. Previously we used it for the kitchen too, and that was horrible. They cycle on and off as you turn the water on and off, which means your hot water pipes are continuously giving you blasts of ice cold water as you try to do dishes, unless you just let the hot run the whole time.

Also, I think the one we got (250,000 btu burner) ends up using more gas than the old tank heater.

But the floorplan didn't work with the tank, so it's probably worth it.

On some of our houses, per the homeowners request we installed a Grundfos recirculating pump, which circulates the water in the hot lines throughout the house, giving you instant hot water when you turn the faucet on, when the pump is running. It had a built-in timer so it would only recirculate the water during peak times of use, so you aren't paying for heating water in the lines during times that you are not home or when sleeping. Just an option.

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Old 01-15-2010, 10:11 AM   #9
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I DIY installed a propane tankless heater in the log house my wife and I built. It was easy and took little time. But I did pay the gas company to put in the gas line to it.

The thing that can be difficult is the venting. Besides a bunch of code restrictions on venting under eaves and near doors and windows, the double-wall pipe is quite expensive.

I had no issue with the warranty being voided because I did the installation myself.
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Old 01-15-2010, 10:23 AM   #10
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The warranty was voided for a DIY installation. You had to supply the installer's license # to validate the warranty.
I'm not too worried about this, I've dealt with consumer warranties and stuck up companies like that before. When it comes right down to it according to consumer protection laws a warranty cannot simply be outright voided and in the event that there is a dispute over the warranty the manufacturer has to prove that the modifications or installation caused the failure or fault in the unit. The only downside is the companies usually think they have the right to void the warranty and you end up having to take them to court over it or at the very least theatening to.
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Old 01-15-2010, 11:23 AM   #11
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On some of our houses, per the homeowners request we installed a Grundfos recirculating pump, which circulates the water in the hot lines throughout the house, giving you instant hot water when you turn the faucet on, when the pump is running. It had a built-in timer so it would only recirculate the water during peak times of use, so you aren't paying for heating water in the lines during times that you are not home or when sleeping. Just an option.
Surely you can't do that with a tankless heater!
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Old 01-15-2010, 01:42 PM   #12
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There was another post here lately about tankless water heaters and the issues involved as far as a DIY installation. I made the comment that IF it were myself wanting to put one in, I would check local codes as to a DIY installation. In my area you, nor I, can even buy a tankless water heater. They are only sold by licensed installers, and actually here they are only sold by the three (3) local LP gas suppliers, whether they are natural gas, LP gas, or electric. IF someone around here were to obtain a gas fired unit, they would not be able to buy the tri-wall vent piping needed to meet l0cal code as this would only be available from two supply house here which would ask you for your HVAC license.The big box apron stores are not allowed to sell them. The local electrical supply houses don't handle the electric models because of local code hassles. Ain't life wonderful? David
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Old 01-15-2010, 03:21 PM   #13
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IF someone around here were to obtain a gas fired unit, they would not be able to buy the tri-wall vent piping needed to meet local code as this would only be available from two supply house here which would ask you for your HVAC license.
... unless they had the internet, in which case someone could mail-order everything.

I wonder what your local code people were thinking when they made that choice -- the outside of my double wall vent pipe barely gets warm after the longest showers.
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Old 01-15-2010, 04:18 PM   #14
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Lofar.
How did you determine that your pipe sizing to the area that your installing the tankless is large enough.

Did you measure the pipe length from the meter to the tankless area?
If so, how long is it? And did you include all the other appliances that will be tapping gas from that line.
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Old 01-15-2010, 08:32 PM   #15
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Surely you can't do that with a tankless heater!
Sorry, I reread your post and realized you were talking about tankless heater, I was thinking you were discussing a standard water heater. I don't think you can use a circulation pump with a tankless, but I could be wrong. Sorry to mislead anyone.

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