Banging H20 heater

[Copymutt]

I wondered over here from Garage Journal. Great bunch over there, but could not answer my problem with a Propane, direct vent, White brand water heater. 38 gallons iirc.
I need to preface the issue w/ the fact that it is now 18 yrs. old. Before you banish my question w/ the obvious answer, understand it has been drained for the last yr. Prior to that it has been a weekender home since it was built. In fact the last 5 yrs. it has been an empty residence, but heated and water on.
Now the issue is a banging noise. It only happens when you draw hot water and the burner is on, no other issues. It has done this since we purchased the home in 2004. I installed a 3/4” nipple on the drain, drained it. No sediment at all. Inspected the internals of the tank with a boroscope and it is clean. Water is via a rural district and high in chlorine. Temp. Is set to low side of Hot. Relief/temp valve is free. Vent is clear. Flame licks are blue and about 2 1/2”
My analysis, the only thing I can imagine is that cold incoming water hits the bottom plate and it contracts, making the noise. Unfortunately the dip tube is welded in place or I would shorten it a bit to confirm my suspicion. I’m probably wrong anyway as it’s seams they would all do this.
Anyone have an idea of what’s going on? Home is on the market.
Thanks in advance.
Jim

 

[voletl]

Is it a large bang that happens once or is it multiple little pops and bangs that happen periodically throughout the heater Heating

 

[Copymutt]

A series of loud pops for sure, and only if burner on and a hot tap open.
Thank you for the reply. Notice your from NY, I’m originally from finger lakes, now Co.
Jim

 

[voletl]

The only thing that I could think of is a lot of times when there is sediment on the bottom of the tank it restricts the water from actually touching the bottom of the tank so that when the water does seep through and it touches the hot metal it instantly vaporizes to steam and you hear a pinging and pop sounds even though you said that there was no sediment when when you flushed it I still suspect that there may be a layer or two on there

 

[Copymutt]

Thanks, I’ll ck again. I’ve experienced that in the past w/ other heaters, but the noise was present any time it was actively heating. Might get up there this weekend.

 

[voletl]

Maybe a deffective tank metal bending

 

[Copymutt]

Maybe, I spoke w/ the manufacturer and they had no clue. When I inspect this weekend I’ll try to mechanically tap the base from the inside to confirm it’s actually metal and not a firmly consolidated deposit.
Jim

 

[Riickk]

IIRC the only difference between a propane & natural gas heater is the size of the nozzle opening.

Since you're selling the property, guessing you're concerned with building inspection. With all the testing, inspecting, etc., just replace it; they're not as cheap as they were, but about $350 will cover it.

You can be sure a competent building inspector will point out to your buyers that water heater is old and liable to fail. Buyers will think that $1,200 or higher.
Replacement is a good investment.

 

[Copymutt]

Rick,
What brands are you seeing for that price?
Thx. Jim

 

[voletl]

Let me know where I can get a gas water heater for $350 also $1,200 is around where I am what it costs to replace a water heater

 

[Jeff Handy]

As mentioned, there is probably a rock hard mineral layer covering the tank bottom.

18 years is about 6 to 8 years past time to replace.

As mentioned, have it replaced now, or buyers will want a big chunk to do it themselves after closing.

 

[MASTRPLUMB]

The calcium is built up around the flue pipe,
when it starts to heat up steam builds up in the little pockets and then explode off, that is the popping
noise !

 

[Riickk]

Mea Culpa, have not kept track of huge rise in price.

Lowes:
Gas $389 40 gal
Propane. $569. 40 gal

 

[Copymutt]

The calcium is built up around the flue pipe,
when it starts to heat up steam builds up in the little pockets and then explode off, that is the popping
noise !

Sure fits the symptoms. I don’t see verification w/o destroying the tank. Bottom line, as Jeff mentioned, even w/o issues it still will attract an inspectors comment to a buyer due to age. Rick, I’ll be ck’ing out that Lowe’s deal. Thx.
Jim

 

[TomFOhio]

I always asked the customer if it sounds like pop corn popping. Uses more gas because it is trying to heat the calcium
and the water. In your case I would replace it .