Atwood Tankless Water Heater Replacement

My wife told me she wouldn't move in to our Airstream until we had hot water. She did, and used the RV park showers until ours was fully operational. The pressure was on! Here's my experience with installing an Atwood On-Demand or 'tank-less' water heater that we just replaced in our new to us 1983 31’ Airstream Sovereign 'Beatrice.'  

Having worked on the plumbing for quite a few days, we finally got to the point where we were ready to test the water heater.  It didn’t work by just flipping the switch on.

Our original unit was also an Atwood, and the manual advised that if the light comes on for longer than six seconds that you should turn it off and turn it back on.  If that doesn’t work, then perhaps it’s not getting gas or something else is not lighting.  When you turn the unit on, the electronic ignition switch should spark. The key indicator that things were not working at all was no spark whatsoever.

The other indicator that things were probably not going to work was that the unit was already 30 years old.  Should we have gone through troubleshooting and tweaking and got it working, most likely it would have been short-lived. There was a good amount of rust on the outside which didn't help the case for trying to save the original hot water heater.

Should we have decided to repair we would have started with 3 things:
1. Ignition parts
2. Gas regulator
3. Gas line going in

Based on other completed repairs, I estimate a couple of hundred dollars with multiple trips to the store for parts and who knows how long to figure out the puzzle. Since we had moved in and were living in Beatrice full-time, hot water was something we really wanted to get going as soon as possible.

We looked at several models, but ultimately decided to get an Atwood because the original unit was an Atwood and we thought that the dimensions would match up more closely.  

Initially, we checked out the 6 gallon model, which was the same unit that was in there. Looking at the 10 gallon model, the dimensions were just not going to work.



Then we happened upon the Atwood On-Demand offerings, and discovered two options, 45000BTU and 50000BTU.  Since we have no plans to camp in bitter cold, we opted for the 45000BTU. Upon successful installation, we have been very happy with it. Now let's get into the details of the switch...


This picture shows you the original 6 gallon hot water heater. You can see some of the original polybutylene pipes still hooked up at this point.  

Once installation of the new water heater was complete, we actually ended up with more space inside the compartment.  If you look carefully in the picture above you can see light coming in from the outside, that is from where the frame had rusted through.  That is a different article for a different day.

This image shows taking the old gas line off of the original water heater, make sure to use vice grips to hold the receiving valve steady, both for removal and installation.  



One of the challenges of removing the original unit was a 1/2 inch flared connector on the gas line that was too large to fit through the gas line hole.  Basically I cut the old water heater metal flange around the flared connector in order to get the flared end out intact. I used a Dremel tool and fortunately, the metal was fairly thin, so I was able to get through pretty easily.  Now, if you do have a problem and you need to reroute it, you may need to put on a whole new flared end.  I would suggest getting a flare kit in order to do that.  This adds a little layer of complexity because you need to be careful and precise. There are videos on-line on how to do that.  

The new Atwood Tankless water heater gas line is routed a little bit differently inside of the trailer than the old one.  



The original line was on the left, just to the outside edge of the heater, and then was snaked through into the trailer compartment.  I think I prefer the gas line routed to the outside compartment rather than the inside the unit itself in case of leaks. Fortunately, I was able to extend the existing pipe along pretty easily by just putting a yellow extender hose from Home Depot on there.  And that fit perfectly.  

Another tip to do is add some putty around this hole.  That way, as you have vibrations and shocks and you’re going down the road, you won’t end up with a leak later on around there.  

Once you get the old water heater out and you have your flared ends, you want to prepare your plumbing.  I was already repairing all of my plumbing, so I opted to go with two quick disconnect ends.  

It’s a bit difficult to see in the background there, but the one end is a quarter-turn valve.  That lets me turn off the cold water supply and actually isolate the water heater as I need to.  The other end that you can see there goes to the hot water, so it comes from the hot water heater and travels back to the shower and the sink.  You can also see that the insulation is in very good condition.  Right above, there is the hose to the furnace.  The hot air furnace hose is just above there.  This was actually draped down over the water heater itself.  And so, just to make life easier for me, I took two bungee cords and just tied it up so they got out of the way while I was working on this project.  That made it a lot easier.


One item I took extra time with was attaching the quarter-turn valve that would let me isolate the water heater if need be.  Turns out this is a handy thing to have around during the installation and allows the sink and toilet to keep working while working on the water heater.  

You can see that I prepared the hose for its new receptor by routing and bending the hose a little bit to the left.  Fortunately, the new water heater has smaller dimensions than the old one and so I was able to route the gas line right around the old one without having to cut it.  

One hiccup I encountered was not getting enough gas flow.  I suspected this was because the propane regulator on the trailer was very old (also make sure to get one these and one of these to hook your grill to the big tank).  The other thought was that I may have kinked the line too much in bending it around the water heater. Replacing the regulator ended up fixing the issue.

You can see the heater unit on the left hand side there, and then that’s where the hoses are routed through and where the heating actually happens.  On the right hand side, you see the red block.  That’s the regulator that controls the water flow.  



This image below shows the water heater outside, along my Dremel kit.  I found the Dremel to be an invaluable tool, both with the removal of the old unit as well as when I was working on my plumbing.  The fittings, the metal straps that you use with pex, are very hard.  Along the way, I made a few mistakes and needed to remove some clamps.  You can use the Dremel to cut it without damaging the rest of the hose, which makes it a very useful tool when you are working on the installation.
Also the water heater is upside down; I was doing a fair amount of dry fitting with the pipes in order to purchase enough pipes and the right parts.    


The image here shows just the plumbing behind the toilet.  I just wanted to get a shot of that while I was in there anyway.  I wanted to make sure that I inspected the plumbing to make sure that it was in good shape. Best not to assume anything when you buy a 30 year old trailer that has been in storage for 15 of those years.


I do, of course, recommend testing everything before you have everything permanently tied down. This simplifies the installation, by letting you wiggle the water heater around a little bit left to right and be able to get to different fittings.  

When you're ready to mount it for real you want use a putty substance.  And that’s putty you can buy at Home Depot or you can buy it online.  You want something like this because it’s very flexible and it’ll never really dry out.  It creates a nice air-proof/water-proof seal.  This is a good product and created a really nice seal. My tactic was to put it on very thick and then squeeze out and remove the excess when screwing the door into place.



Fortunately, because I already had an Atwood water heater that I was replacing, I was able to use the same screw holes on the left and right sides of the flange.  The top holes didn't quite fit correctly, so I used self tapping screws, in order to screw it in.  I did try to use a regular screws, but what I found is it’s difficult to puncture through the skin as well as whatever the surface is back behind there.  What seems to happen is the aluminum skin lifts up as you’re screwing in and then you reach something very hard and you have to press very hard in order to get the screw to set and it doesn't even really want to grab.  I did buy some small, short self tapping screws and those were definitely the easiest to use.  They screwed in and "sat" down very quickly.  

The last thing you can see in the image here is the wiring as well as the nipple.  So there are three different wires: green, red and blue.  Red is hot.  Green is the ground.  And then the blue is the, I think the negative, but it also acts as the indicator light.  So during the operation of the furnace, if it’s sparking and it’s trying to light the furnace in there, the indicator LED light will turn on for a brief period of time.  Now, it should turn off almost immediately once things are going.  And that’s how you would know that there’s a problem, if that light stays on.  Either it’s not getting enough gas or something along those lines.  


Using the flexible gas line gave me some nice, no pun intended, flexibility to have it end up exactly where it needed to be.  From edge to edge, you’re looking at about 11 inches. 

I bought a 24 inch gas line and that seemed to be just perfectly enough for my installation.  I was fortunate because the gas line had already been routed fairly close to the one side. Be careful of getting the right size line. After a wrong size purchase, I ended up taking the entire original hot water unit with me to Home Depot to get the right one.

The size that worked for me was 1/4" I.D. x 3/8" O.D. Tube, 1/2" Female Pipe Thread x 1/2" Male Pipe. Make sure you use the "Yellow" pipe tape whenever you're working with gas fittings, as well as purchasing some proper leaker tester. The stuff that I bought - while it seems it is just soap it seems to give off more bubbles when testing fittings.



My unit came with two connectors that have a half inch pipe thread on the one side, and then a SharkBite-type fitting on the other.  That just slides directly on to the copper pipe that is in the water heater itself.  Then I just routed it through like you would normally.  Now, of course, if you have copper, you could go straight to copper or you can go to pipe or you can go to PVC.

Looking back at my list of items needed to do this installation it became larger than expected. If you are converting from Polybutene it makes the job more challenging, and the list a little longer.

List of plumbing supplies I used:
Crimper
½ pex pipe
Sharkbit ½ Tee (5 pack)
Sharkbit ½ Elbow (5 pack)
Pex Clamps tape
Pipe Cutters

During the door installation I needed to modify it a little bit.  It was rubbing up against some of the trim molding on the side.  By using a Dremel tool, I was able to route out around that trim piece, so it will sit flush.  Also just yesterday I was able to paint the door grey "Aluminum 7515" in order to match the Airstream. It matches very nicely.

And now, for your viewing pleasure: videos of the finished installation.

And from the outside.  

If you enjoyed this article and wish to purchase some of the items above using affiliate links I would greatly appreciate it!

Thank you for stopping by.  If you’re considering water heater installation yourself, I wish you the best of luck and hope this article was helpful in some way. Feel free to ask me a question or leave a comment in the blog or on facebook.  
Patrick 
~1983 31foot Sovereign “Beatrice”
~1984 Toyota Dolphin "Bertha" 
~1984 West Wright Potter 19 "Nelly"