Tankless water heater installation

When we were doing the HVAC system upgrade, one of my friends at church got me in touch of a friend of his that had a tankless water heater he had bought, but couldn’t use.  I purchased it from him for $500….much cheaper than I could have purchased one for.  The unit had never been used too, so this was a good bargain, and an excellent upgrade to save energy, and space in my workshop.



One of the problems with the workshop in the carport was that it only had a single incandescant light fixture in it.  This was going to be problematic working in the dim light.  I had two 4-food fluorescent lamps I had removed from the old house before I demolished the shed that came in handy in resolving this problem:

20140726_152544…It was hot that day I put the lights in though, so upgrading the water heater, I decided to wait till September when things were a bit more comfortable.

First step in the installation was to mount the water heater on the wall.  I added a piece of old plywood to the wall to hold the water heater, and the associated plumbing.

20140907_213215Now, I ran into a glitch.  As you see in the above picture, the exhaust pipe exits very near the top, as I “test fit” it here. The only problem is that it was too close to the soffitt when it exited the house, so I ended up having to move the water heater down after mounting it….rookie mistake!  It looks okay inside the house, but outside, the soffit hangs lower than the top of the wall.  20140911_193228This is much lower than I had originally planned, but the proper distance so the exhaust pipe has plenty of clearance with the soffit on the outside of the wall.  Next step, after the water heater was mounted was to cut the hole and install the exhaust pipe:


Now, a word about the exhaust pipes on these units.  They are two designs to tankless water heaters. This particuar one uses a coaxial exhaust pipe.  If you look closely at the pictures above, you may notice that it’s a pipe within a pipe.  The center is the exhaust, adn the outer edge is the intake for combustion air.  This allows the exhaust pipe to be mounted with zero clearance, as the outer portion does not get hot.  The only problem is that you will need to purchase the coaxial exhaust pipe for these water heaters, and they are not cheap…add another $100 or so to the tab for the purchase of this special pipe.

Some of the newer model tankless water heaters use PVC pipe just like the new high-efficiency furnaces use.  These are ultimately the way to go, and the industry is shifting to using this, as models are improved.  This is the way to go, as PVC pipe is much cheaper than the metal coaxial pipe.


Next step of the process is to install the plumbing to the water heater.  Instructions call for 3/4 inch gas pipe, and water lines for best performance.  Now, in our house, the water lines going to the old water heater were only 1/2 inch, so I used reducers to go between 3/4 inch plumbing at the heater, to the 1/2 inch existing house lines.

I plumbed up the gas lines first, and then made all the water lines.  I worked my way from the water heater back to the house plumbing to minimize down-time of not having hot water.  I also did the change-over on a weekend when my wife was out of town on a church retreat, which meant that I could do without hot water for the weekend.  Here’s some photos of the plumbing…I tried to make it as neat as possible.

20140920_210654This is a picture of the gas line on the other side of the wall, behind the water heater…it’s the utility room.  The pipeline going horizontally is the main, the furnace is towards the left, and the line going vertically through the wall, is for the water heater:


Now, if you are wondering about something here….Some people connect these water heaters up with bypass valves so they can flush them out when they need cleaning.  A cheaper alternative to this is to use the flexible lines like I did.  All you need to do is cut off the water to the heater, and then use a monkey wrench to disconnect the water heater from the plumbing, and connect it to your flush-out kit.

20140908_213818Another important thing you see in this picture above is a pressure-relief valve on the left side there…that is just as important on a tankless heater as on a tank style water heater.  The discharge of this valve needs to go to where the water can drain without damaging anything….mine just simply goes to the bottom of the wall, and out a small hole to the outside.

20140926_223331Here is what it looks like with all the plumbing in place! The leftmost pipe is the gas line, and the red valve cuts the gas off to the heater.  The center line is the cold water input, and the blue valve there is to cut the cold water off.  The third pipe over is the hot pipe into the house.  The tap at the bottom of the pipe allows the how water plumbing in the house to be drained…it also is a nice tap for connecting a hose up for hot-water car washing and when ever you need hot water outside.

Next step of the project is to install the thermostat control.  This allows you to adjust the water temperature depending on your needs.  I installed ours right next to the kitchen sink…that switch on the left is for the garbage disposer.  When using the dishwasher, it works best to turn it up to the hottest 140 degrees.  For hand washing, abou 120-125, and for showering, about 100.  Whatever temperature the thermostat is adjusted for, the water heater will instantly produce.

The challenge was installing this thermostat and running the cable to it.  All the bathrooms and the kitchen back up to a plumbing shaft going up the center of the house.  It was rather easy to run the thermostat wire up this, and across the attic.  The challenge though was getting it to the workshop area.  I had to use an existing piece of thermostat wire to fish it through.



Last step was to add electricity to the water heater….Unlike at tanked gas water heater, the tankless water heaters require electricity to run the combustion blower, and the little computer inside that detects when you are running water.  The water heater doesn’t take much…paperwork says 3 amperes…I measured it at 60 watts with a tap running wide open.  If you wanted to, you could put a computer UPS on it so that you have hot water when the power goes out.

20140926_223521As  you can see here, there’s lots of electronics inside one of these things!  I took the existing 240 volt line from the old water heater and connected it to a 240 volt plug that will be used for a shop air compressor 🙂

Here’s what the workshop area looks like with everything done.  My table saw now stays in the spot the old water heater was in, and there’s plenty of room to put a few bikes in there too:


The old water heater?  Well, I drained it, pulled it out, and gave it to some friends at church that have 6 kids and needed a new water heater.  It was not that old, and had very little use, since the house sat empty for a few years.

water heater install

CONCLUSION:  In all, this is sort of a complicated job, that I could see costing almost $1000 for a plumber or mechanical contractor to do…it took me about 6-8 man hours, and about $130 in plumbing parts to complete.  I saved lots of money doing this myself.  It takes some planning to do yourself however…you need to locate where your plumbing lines are, where you want to exhaust the heater, and you need to get electricity to it too….lots of things to consider.  Luckily, with upgrading other mechanical components, I was able to plan ahead and integrate the projects.

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One Response to Tankless water heater installation

  1. Pingback: How to solder copper water line | Audvidgeek's Blog

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