Gas Hot Water Heater Noise
 

I have a gas hot water heater and I recently was in the garage when the water heater started up. I hear several low clunking noises as it first starts and then the noise stops as the heater goes through its heating process.

Water heats well, no leaks, expansion tank seems to be functioning. I have talked to others who have noticed similar startup noises.

Wondering if someone else has experienced the condition and knows the cause? Defective sacrificial anode comes to mind.

I remember similar noises with the gas fired water heater up North, I just took these as the normal thermal expansion noises. Heater was working fine several years later when we sold the house.

Sounds normal to me. Thermal expansion and sediment moving around.

Normal noises

It is the sediment being forced up by the heat. It is not normal if you have been draining your tank monthly. Monthly tank draining is covered in your owners manual. People mistake this as 'normal' because few bother to maintain their water heater. Sediment does impact your HWH tank's life expectancy, this is why it is in the manual.

Very hard water here which produces lots of sediment, probably the cause of the rumbling and knocking. I drain 5 to 10 gallons out of the bottom of my tank every 9 to 12 months and am astonished at the amount of white crystals that come out.

If you drain your tank, be prepared for the drain valve to drip after you close it, from sediment left in the seating area. I changed out the cheap globe valve to a full port quarter turn ball valve and no more problem.

Thanks for the responses. Has anyone changed out the Anode ? Supposedly a consumable.

I have. It took some effort as the rod was quite corroded. Most tanks use an aluminum rod. I replaced mine with magnesium. Magnesium helped with the sulfur smell in the water, this was in a different state.

Good article on the how and why of draining the water heater:

Why Is My Water Heater Making a Knocking/Rumbling Noise?

I had noises from my HWH for about 8 years, this was in Bucks County, Pa. very hard water, similar to T.V. It never leaked and remained working fine (except for the noise). That HWH lasted 18 years. I finally did change it out, but those noises are related to a build up of sediment. Not harmful in any way, but causes your heater to be less efficient.

I’m have this noise issue with my new furnace! The AC company tested the gas pressure coming into my house and found it double what it should be. First question he asked was does my hot water tank make noise? And what about the gas flame on my stove? Gas company coming out today, to check. Gas regulator either set too high or bad regulator. Have you had the gas company check the gas pressure coming into your house?

How much does it cost to have a rod replaced and how long do you wait before doing it? Will this allow the water heater to last longer?

Wish we could drain our water heater! However, when Mike Scott Plumbing installed it (8 years ago when the house was built...we’re 2nd owners) they left the valve turned down into the pan. Impossible to get at the valve now.

Had same problem with hot water heater ,got 90 degree bend washing machine hose take 5 gallons out every year before I go back north still like new inside water heater only last 5-6 years if just left alone. If you have to replace high efficiency model more expensive but cheaper to run cost in 3 years would make up difference

Not a difficult fix. Make sure your pan is plumbed to the outside. Turn off your water to your house and open faucets in sinks and outside your home to drain all the pressure and water out of the lines. Take a wrench and unscrew the valve on the water heater slowly allowing the water to drain into the pan. This will take a while so do this when you are not going to need water for a while. You can now either replace the valve with a different style or use the old one positioned in a more convenient position. Be sure to use pipe wrap and have someone standby when the main water is turned back on.