Water Heater Problem

[extropic]

I have a natural gas water heater with a standing pilot light with a piezo electric igniter.
I think the unit is about 2009 vintage.
Last Sunday I took a not hot shower which informed me that there was a problem.
There were no external signs of a problem with the heater.
There is a tiny glass window that one is "supposed" to be able to see the pilot but it's impossible with any ambient light.
I waited until after dark and the pilot relit as it should.
However, no hot water again Thursday night as I was going to wash a few dishes.
There has been no recent gas utility work on my street or in the area (that I'm aware of).
I relit the pilot this morning.
The heater lives outside the house, inside a metal enclosure and we have had no high wind events lately.
The pilot has never been blown out in previous high wind events.

My questions:
What additional information do I need to provide to get useful replies?
Is the symptom I've described common?
Does the symptom indicate a particular part/assembly needs cleaning or replacement?

 

[benmychree]

Does it have a thermocouple? This is a copper tube that is connected to the gas valve and the other end impinges on the pilot flame. If so, try replacing it, any hardware store should have one.

 

[extropic]

Does it have a thermocouple? This is a copper tube that is connected to the gas valve and the other end impinges on the pilot flame. If so, try replacing it, any hardware store should have one.

I haven't taken it apart yet.
The works are not visible without disassembly so I'm not sure what type of pilot flame sensor it has.
I assume it has some sort of pilot flame sensor that interlocks the gas flow to the main burner.
No pilot = main gas flow won't open.

After I relight the pilot and then reset the thermostat, I can hear main burner gas flow and the vent air is getting HOT.
That suggests to me that the pilot flame sensor is working.

 

[benmychree]

That begs the question of why it shut off --- If it does it again, I'd suspect the thermocouple is going bad., We replaced out tank heater with a tankless type, you never run out of hot water, unless you lose power, but of course the generator brings it back up. Our gas bill is markedly reduced.

 

[extropic]

The pilot flame sensor may be intermittent?
If it goes open, gas to pilot is shut off.
Is that a common problem?

 

[mksj]

Thermocouple almost always fail over a period of time, they have a finite lifetime. They generate a low current which keeps the valve open, this includes the pilot light. Typically when lighting the water header you need to turn the controller gas valve to the pilot light position and depress it until the pilot light is lit and on for 1-2 minutes. If the thermocouple fails or intermittent then the pilot light will go out and no gas = no heat. I have also had the coil in the gas controller go.

 

[extropic]

@mksj

Thank you.
That's good stuff. Even I can follow those tutorials.
I'll test the thermocouple later and report back.
I've only had water heaters develop leaks. At this house, the previous water heater lasted over 30 years. No previous controls problems at any other water heater.

 

[woodchucker]

Do you empty the sediment out yearly?
I attach a hose and drain until clear. More important for a gas fired unit since it heats from the bottom.

 

[RJSakowski]

Do you empty the sediment out yearly?
I attach a hose and drain until clear. More important for a gas fired unit since it heats from the bottom.

There can be problems with the electric water heater too. The lime would deposit on the heating element and eventually fracture and fall to the bottom. Before I went to softened water , the deposits would amount to several inches deep annually. The deposits on the elements would act as an insulator, causing the element to fail. Since I went to softened water 24 years ago, I haven't had to clean the tank or replace an element. The water heater is going on fifty years old . I keep hoping it will fail so I can replace it with a hybrid unit but it's like that damn bunny.

 

[woodchucker]

There can be problems with the electric water heater too. The lime would deposit on the heating element and eventually fracture and fall to the bottom. Before I went to softened water , the deposits would amount to several inches deep annually. The deposits on the elements would act as an insulator, causing the element to fail. Since I went to softened water 24 years ago, I haven't had to clean the tank or replace an element. The water heater is going on fifty years old . I keep hoping it will fail so I can replace it with a hybrid unit but it's like that damn bunny.

I know, when I moved in my water heater failed in a year or 2. Electric, I could not get all the water out, the sediment blocked the drain, and there was probably 70- 80 lbs or maybe more of sediment in there.

That's why I drain it regularly. If I have to do it again, I want to make sure I'm not dragging that much weight up the stairs.