Should I replace water heater thermostat

[Weedguy]

Have a 6 YO 50-gal, dual element electric water heater, and the water temperature has slowly declined to the point where you can almost shower on 100% hot water.

When it was new (and or previous 10 YO water heater), 100% hot at the faucet was almost dangerous! Run the shower on 100% hot and you could get lost in the fog :-) . Not anymore....100% hot on the faucet = a nice warm bath. (P.S. the water temp is the same around the house- so it's not the bathtub faucet).

The themostats are set on the highest setting, I have checked the reset button- and it did not seem to be tripped.

I "turned the thermostats back and forth" and things got a little better, but not a big change.

The heater seems to "work well". Sure you can do a load of laundry on hot AND fill the bathtub on 100% hot at the same time and that will exhaust it; however 30 min later, the water has returned to the "hot but not as hot as we'd like" level same as when it's rested for hours.

Also, two folks can take relatively long showers at the same time and we never seem to exhaust it.

So, I conclude that the elements are working fine- it's just that the thermostats have somehow "changed" and shut it off before it gets "hot hot".

I've got a few key questions:

Do thermostats normally "loose it" or change over the years?

Is installing new thermostats a 95% guaranteed fix for my problems?

OR ARE MY THERMOSTATS LIKELY OK BUT there's likely some affect of precipitates forming on the elements or tank that "trick" the thermostats?

I'm concerned that the thermostats are basically an "external" item and am scared that it's likely that slapping on new thermostats won't fix anything????

Advice from anyone with experience?

Thanx!

[Hube]

one item to check out is the "DIP TUBE".This "dip tube" allows entry of cold water to go to the tanks bottom and allows the already heated hot water to go out.
But if this dip tube is shortened/broken, it lets any cold incoming water to mix with hot near the top of the tank.
The result; cool (not hot) water goes out, instead of hot.

[HayZee518]

Water Heater

Borrowing one of lazypup's diagrams here's an idea of what's inside one of those heaters. The thermostats are not in direct contact with the water but are surface contact with the tank body. They slip into a clamp that is welded to the tank proper. The elements either bolt into or screw into a bung hole at the top and bottom of the tank.

[Weedguy]

Ok, this thread is taking a direction that I don't know what a dip tube is...I do!

But, why would a dip tube cause a GRADUAL decline in temperature over a number of years? This is a 6 yr old heater, I imagine the dip tube is plastic, so I don't see it gradually eroding away, and the heater worked great when we got it, so I doubt it's damaged or defective.

I'd really like an answer to my questions:

Do thermostats normally "loose it" or change over the years?

Is installing new thermostats a 95% guaranteed fix for my problems?

OR ARE MY THERMOSTATS LIKELY OK BUT there's likely some affect of precipitates forming on the elements or tank that "trick" the thermostats?

I'm concerned that the thermostats are basically an "external" item and am scared that it's likely that slapping on new thermostats won't fix anything????


If the answer is "Thermostats are pretty darn reliable and dip tubes cause a ton of problems, and you didn't list a leaky dip tube as a possible cause" then Ok, thanks for the advice...

Sorry to be ungrateful, but, "This diagram explains why a leaky dip tube is one possiblity" doesn't help.

Thanks.

[Hube]

Ungrateful,but sorry.

Your statement...."sorry to be ungrateful" says it all.
you are ungrateful, but so sorry.
Good luck

[HayZee518]

Ok, this thread is taking a direction that I don't know what a dip tube is...I do!

But, why would a dip tube cause a GRADUAL decline in temperature over a number of years? This is a 6 yr old heater, I imagine the dip tube is plastic, so I don't see it gradually eroding away, and the heater worked great when we got it, so I doubt it's damaged or defective.

Anything manufactured is prone to failure the tube is plastic or teflon

I'd really like an answer to my questions:

Do thermostats normally "loose it" or change over the years?

Thermostats are a bi-metallic element that bend when heated in one direction then relax back to their original flatness when cool. They have a contact welded on their surface. I had a heat problem on my heater when I moved in here 6 years ago. I replaced my lower "stat" and haven't had a problem since.

Is installing new thermostats a 95% guaranteed fix for my problems?

OR ARE MY THERMOSTATS LIKELY OK BUT there's likely some affect of precipitates forming on the elements or tank that "trick" the thermostats?

If you are in an area known for high liming or sulfur deposits then I would suspect a coating on the heater elements. The scale insulates the elements against effective heat transfer. They won't "fool" the thermostat because the "stat" is monitoring the overall tank temperature at that level it is mounted to. Hot water stratifies to the top of the tank because heat rises.

I'm concerned that the thermostats are basically an "external" item and am scared that it's likely that slapping on new thermostats won't fix anything????


If the answer is "Thermostats are pretty darn reliable and dip tubes cause a ton of problems, and you didn't list a leaky dip tube as a possible cause"

Hube did!

then Ok, thanks for the advice...

Sorry to be ungrateful, but, "This diagram explains why a leaky dip tube is one possiblity" doesn't help.

Thanks.

My response to your questions are posted above in the quote

[Weedguy]

I had a heat problem on my heater when I moved in here 6 years ago. I replaced my lower "stat" and haven't had a problem since.

Thank you....I think I'll commit my $20 I spent on thermostats yesterday and install them.

Yep, while our water has some calcium, it's not a huge problem in this area, and the heater seems to exhaust itself normally (gradually cools to cold when you fill two bathtubs at once with just hot water turned on) and then recovers in 15 to 30 min, so the elements seem to be doing their job.

And I really don't think it's the dip tube as the water is never HOT. If it was the dip tube, I'd expect at least a short period of scalding water.

[Weedguy]

Ooops...double post

[LazyPup]

I have rerviewed the original question in detail and come to the conclusion that i doubt this problem is related to the water heater at all.

Weedguy has stated that this is a 50gal water heater from which they are able to take two simultaneous showers or simultaneously fill two bathtubs. That in itself it quite remarkable when one considers that the anticipated first hour deliver rate for an electric water heater is 65% of the total tank volume at a temperature 10degF below the thermostat calling temperature. This means that if the thermostats are set at the code maximum of 125 we could expect to get 32.5 gal. at 115degF.

I would be more inclined to believe the problems that he is noting are not in the water heater but are related to external conditions.

We must understand that our water supply line is only required to be buried 6" below the average frost depth for any given area. In summer our incoming cold water will normally be equal to the average geothermal surface temperature of the soil which is about 50 to 55degF. In mid winter as frost enters the surface the incoming water temps often drop to 34 to 40degF. As the temperature of the cold water drops obviously it would require longer time for a water heater to recover between uses.

We must also consider that as we draw water from a water heater and equal amount of cold water is being drawn in, and that cold water will have the effect of dilluting the stored hot water in the tank, thus the colder the incoming water the greater the rate of dilution leading us to believe the water heater is not heating the water as fast as normal.

[Weedguy]

I have rerviewed the original question in detail and come to the conclusion that i doubt this problem is related to the water heater at all....

NO WAY LazyPup

1) When the water heater is "rested" overnight, with the thermostats set to high (ABOVE 125), and you initially turn the water on, it is not nearly as hot now as when the heater was new....Through the whole run, the temperature is cooler.

All of that talk about two showers was to show evidence that I think the elements are working quite well.

Number two is that I have discovered some improvement since I took my screwdriver and rotated the thermostats back and forth...telling me that the problem is the thermostat as I originally suspected.

Funny forum here- no one has ever answered my question: "Think it's a good idea to replace the thermostats?"

I mostly get alternative explantions that I failed to list in my initial post.

[JCA1]

I think it's a mineral deposit problem. Properly flush the tank and try it then, if no improvement replace the upper t-stat first and try it.

[LazyPup]

I am not in the habit of changing out any component unless I am certain that it is defective..but if you have your heart set on replacing the t/stats have at it. You can't hurt anything in the process and you will only be out about $30.