Water heater repair

Saturday morning, we awoke to find no hot water.  The pilot was out on the water heater and it would not stay lit when I pressed the igniter button.  Of course, it was a holiday weekend (isn’t it always?), so we just did without for a few days.  We had a kettle and the stove was still working, but hot showers were unavailable.

I invoked the power of the INTERNET! and searched for knowledge.  The usual cause of “pilot won’t stay lit” is that the thermocouple has failed, so the water heater cannot sense that the pilot is on, so it stops feeding gas down the pilot tube in order to prevent an explosion.  I found a set of owner’s manuals at the manufacturer’s website.  None of them exactly matched my model, but the interesting thing was their owner’s manuals include instructions for “replacing the thermocouple”, implying that this repair does not require a plumber’s licence.  I usually limit myself to electronics repairs.  I generally don’t do plumbing, and have never done a gas-line repair before.

I followed the disassembly instructions until I was able to remove the pilot-assembly, shown here.  The top item is the thermocouple, the middle item makes a spark to ignite the pilot, and the bottom item provides gas for the pilot.  Thankfully, on this model the pilot’s gasline has a screw coupling, so I didn’t have to bend the gas-tube for access, then carefully (one of several places in the manual where they warned me to be careful) bend the thing back for re-installation without cracking it and causing an explosion.

Online sources told me that water-heater thermocouples are generic; the only thing that matters is the “length”.  I thought they meant the length of the tip part, but actually they meant the length of the copper tail that connects the thermocouple to the control unit.

On Tuesday I set out to buy a replacement thermocouple.  Since this is a rather specialized product, I decided to skip Home Depot and drive directly to One Stop Plumbing.  I brought along driving directions for Mark’s Supply as a backup.  The guy at the counter at One Stop said they didn’t have it and suggested I go to Mark’s Supply — for which I already had directions!

The first sign of trouble was the sign outside Mark’s front door: “Contractor and Trade Sales Only”.  They did not want my business, but there was nowhere else to go, so I went in anyway.  I showed the counter clerk my pilot-assembly, but she had no idea what to do — her computer wanted her to enter a part number!  She called someone for help, then went to the stockroom to fetch me a part.  But the thing she got was a thermoelectric generator, which is a totally different part that happens to look vaguely similar and have a similar name.  I was stumped.  Now what?

Another customer, who happened to be in the store and happened to be a gas plumber, took pity on me and told me to look at the end-cap of the aisle behind me, where they were selling thermocouples.  Great!  But which size do I need?  I had forgotten to measure the length of the copper tail.  (I had also forgotten to write down the model number for my heater, as some online sources recommend, but that turned out to be unnecessary.)  The other customer looked at my assembly and suggested that I get the 18-inch model.  Only $8.23!

I drove the 24 km back to my house, then examined my purchase.  The two ends looked right, the press-fit adaptor looked right — but the length was wrong.  There was no way it could work.  I actually needed a 23-inch tail.  So I drove back to the store and bought the 24-inch model.  Only $7.48!  I have no idea why it cost 9% less to buy an item that contains 30% more copper.  Maybe it’s a more popular size?

So now it’s time to complete the repair.  I decided to take photographs of my steps, so this post would have some decoration.  That decision drastically increased the repair time because I am a terrible photographer.  My forepaws shake a lot and — even bracing the camera against a door-frame — it often takes me 3‒6 tries to get a photo that’s sharp enough to use.

Anyway, here is the pilot-assembly with the new thermocouple installed.  The new one has a lighter tip and a brass-coloured ferrule at the bottom.

Here is the pilot-assembly after re-attachment to the burner guts.  In this photo, the pilot-assembly has been flipped over, so now the thermocouple etc are pointing left and the pilot gas-tube is attached on the right.  Once again, I am really glad there was a detachable coupling so I didn’t have to bend the pilot gas-tube for access!

The paint chips at the top-left and bottom-right of this photo are because the back door to my basement is in serious need of a new paint job.

Here we see that the flame-spreader plate has now been re-attached, which partially covers the pilot-assembly (poking out to the left).  Also, the thermocouple and igniter wires have been threaded through the front plate and clamped in a strain-relief thingy.

Note the grey sealing gasket which is supposed to be attached to the front plate, but has partially peeled off.  The manual emphasizes how terribly important it is to have a tight seal around the plate to avoid risk of explosion.  But I thought it would only matter for a moment while I’m screwing the thing into place, so I used two pieces of cellophane tape to hold the gasket in place while shoving the burner guts back into the water heater.

All that’s left is to re-attach the igniter wire, thermal-overload detector wires (not shown here), thermocouple wire, pilot gas-line, and main gas-line to the control unit.

And now, the final act.  Turn on main gas line.  Wait.  Sniff.  No gas!

Turn main control knob to PILOT.  Press and hold red button.  Press black igniter button.  Press black button a few more times.  There is a spark, but no flame.  Shit!

Wait a bit.  Press and hold red button again.  Press black button.  We have ignition!  Hold red button for sixty seconds.  And now, the moment of truth: will things be any better after this repair than they were before, unlike this previous time?  Release the red button.  The pilot stays lit!  Yessss!  The day is saved, thanks to Hero Doggie!

Turn main control knob to ON.  Main burner starts up!  No gas smell!  But, after a few minutes, there is a sizzling noise.  Once again I invoke the power of the INTERNET! to determine that this is probably just water vapour from the burnt gas, condensing on the cold bottom of the main water tank and dripping onto the flame.  Nothing to worry about, but sounds bad.  I decide to go take a nap for half an hour so I don’t have to listen to it.

Upon my return, the heater is quiet.  It has finished heating up the water tank.  There is no smell of gas, but there is a definite “burnt” odour.  Examining the front plate, I see that the pieces of cellophane tape are now crisp and their adhesive apparently melted and ran down the plate.  Oh well, doesn’t seem like a big deal.

And so, once again, the City of Townsville is saved.  My mate and offspring are now provided with running hot water — such a modern convenience!  I will probably never have to do this again, because the Government of Canada is telling people to stop using these old-style water heaters and switch over to tankless models, which do not have pilots.