Home Improvement → Dual Element Water Heater - Hot water doesn't last

I have an AO Smith 40 gallon dual element water heater(DEN 40)in my condo. I don't get enough hot water for 3 people to shower, 2 can do it by limiting their water use. The hot water will run out after about 20 minutes of use. Increasing the thermostat temperature increases the water temperature but doesn't make it last longer. My neighbor who has the same unit had an electrician change the wiring so that the heating elements act at the same time (simultaneous) rather than separately (dual). He now says that he enjoys enough hot water for 4 people to shower. I have tried to find information about this method , but so far I'm not convinced this is a good idea, as it may just suck a lot more electricity, or even be dangerous in terms of electrical load. Any comments?

The other option I'm thinking of is to turn down the top thermostat to 20 degrees lower than the bottom one (now they are set the same). The idea is that since the top thermostat trips the bottom one to operate that I will get the replacement cold water flowing into the tank to heat up sooner, and then provide more hot water faster. Is this a good idea? Would it even help?

When was the last time that the Water Heater was 'Flushed' Out?

Dirt/Sediment can build up inside the water heater, reducing it's efficiency.

There should be a "Hose Bib" valve down near the bottom of the unit... Connect a Garden Hose to the Bib, and run it outside (or into a Laundry Sink/Drain), and slowly open the valve.

Let the water run until it's reasonably clear, then shut off the valve, and see if your Hot Water capacity has improved...

HTH,

-Tursiops_G.

The water heater is brand new. The water in my area is as soft as soft can be. I'm trying to test all possibilities before calling an electrician to find out if there is an electrical problem.

I find it hard to believe any license electrician would be stupid enough to do that. He'd be setting himself up for a big liability suit. Both elements on draw more than the breaker so he'd have to change from the box to the heater.

If it's brand new you might check is the in and out are connected properly or you could have a bad element or stat. A 40 gal is a little small for an electric.

BTW - I think heating problems caused by sediment is more for gas heaters since they heat from the bottom.

Ummm... where do you think the LOWER element, (the one that does most of the heating), on a dual element electric is???

I agree with SparkChaser .

If an electrician rewire the heater he voided the warranty for sure. He had to have run a new wire and put in a larger breaker thus violating code too.

I have a condo in Florida we go to every couple of months. When we're not there the 30 gal electric water heater is shut off. When I turn it on 2 people can shower in about 40 minutes.

Also as SparkChaser said I would have the units' heating elements and thermostats checked. Just because it's new doesn't mean it's working OK.

Don't forget about all the stuff that can come in directly from the Water Main...

I can't tell you how many times I've turned on a faucet, only to find the Water running *BROWN* due to Water Main Repair or Cleaning in my area...

I make it a point to 'Flush' my (Indirect-Fired) Water Heater out each Spring... You wouldn't believe how much Crap comes out of it just in the first minute of flushing...

-Tursiops_G.

Doesn't void warranty.

Exactly jkmlr. The rewiring operation is diagrammed in the manual. The only catch is the electrical load on your panel, not to exceed 40 amps. I don't know what I draw.

Here is the exact manual: »www.hotwater.com/lit/im/ ··· -003.pdf

Not to get too far OT since the OP has a new heater. The lower element is, ummm, "lower" not on the "bottom" On my heater, I'd have to have about 1.5 cu ft of sediment to reach the lower element. Also the element is immersed in the fluid not being heated through a layer of sediment.

BOTTOM line , I'm just saying the sediment is much more of a factor on gas tank heaters.

New information, I never saw one of those, nice heater.

You have to check what elements you have. Standard for other heaters is the 4500 watt. Two of those would be about 37.5 amps. I'd still look for something wrong with the heater before I did the simultaneous thing.

Here's a good picture of the inside of an actual electric water heater that shows several of the problem areas (sediment, broken dip tube). I was surprised too that the lower element is as low as it was. I figured it was higher then what it is.

That one is low. Mine is higher, I measured it before I made the last post about 7 in above the drain.

EDIT: I was curious, since I haven't ever cleaned my heater (8+ years). Al I got was about a pint of brown water. It was all clear after that. Unless it's clinging to the sides somewhere and my 50 gal is 40 gal I must have clean water.

Pull the Dip Tube and most likely it is too short. Talking to my HVAC guy the past week, he even stated that AO Smith is one of those companies that are using Dip Tubes that are too short, which does not allow for enough Hot Water.

Also, the amount of Hot Water avail. for Demand is under 50%.

Interesting. I didn't know that. I wonder if all manufactures allow this?

Yes and yes. The top element should be set to a lower temperature than the bottom element.

let's see, 2.5 gallons a minute for 20 mins for 2 showers means you use 50 gallons in 20 minutes. sounds like 10 ghallons more than the heater can HOLD. as stated above, a WH hold more than it can deliver, since the incoming cold water cools some of the held water down. so realistically you should be getting probably 30 gallons of hot from it before it has to heat an entire tank full back to set temp.

look at the first hour recovery rate of your WH. that is how many gallons you can expect to be usable inthe first hour.

another option is to set the temps as high as they go and then install a whole house tempering valve that will only pass it at 125 or less. this means you will use less hot for the same temp shower.

BTW, we have a 40 gallon tank at our house. i wait at least 30 minutes after my wife takes her shower each morning and i still usually run out about the time i am getting the shampoo out my hair. of course, this is never an issue unless I get my shower first!

That always sounds like a good idea until you read the manual. I had mine set differently until I saw where is says set them to the same temperature.

The manual only states not to turn the top thermostat higher than the bottom one.

Last night I turned it down to 150, the lower element is set to 170. After letting my wife take the first shower, I went in and let the water run without interruption (usually I would turn it on and off several times). The result was no sudden loss of hot water. The temperature declined slowly, but noticeably. By the time I was done taking the luxuriously long shower, the water was still satisfactorily warm.

I was even able to shave with a hot sink of water right after.

Looking good, and hopefully no need to double the electricity consumption by rewiring it to simultaneous mode.

The thermostats are not precision instruments. You should keep them at least 10 degrees apart.

170 is incredibly hot. You'll be increasing corrosion, shortening the life of the water heater and increasing the risk of scalding accidents. You shouldn't need to set it above 135.

I have a ele wtr htr and have noticed the same thing the hot water not lasting as long as it did. I have turned my temps up and it seemed to help a little bit. I was actually giving a thought to going with a instant ele wtr htr. Not sure if they offer any benefits over a tank in the ele side.

A neighbor just replaced his upper element a while back and that seemed to fix his lack of hot water problem.

Maybe one of the elements is bad unlikely since new but maybe worth a shot.

I've turned it down to 130 and 150. Let's see what happens...

Hopefully you have anti-scald fixtures as 170 is really hot.

Time to produce 2nd/3rd degree burns at 150F = 1.5 seconds at 160F less then 1/2 second (my cheat sheet does not go above 160 degrees.

Besides scald danger standby losses will be a lot higher increasing power consumption.

Our local power utility forbids simultaneous operation and limits maximum element wattage to 5,500 watts.

/tom

I know I'll probably get my head bit of, but, a 40 gal. electric water heater functioning properly will not run for more than two people in a row without the use of flow reduction of some sort or self restriction of usage. 40 gallons of water only goes so far and the unit is not designed to heat the water as fast as it comes into it. If it was designed to keep up with that kind of usage it would not meet the energy ratings required today. If you want nothing but hot water without these restrictions you need a much larger water heater (if you don't care about the utility bill) or a demand water heater (costly unit).

PeeWee, you are right. I don't expect it to produce scalding hot water for ever. I do expect it to produce a supply of water that gradually tapers of to luke warm. It used to run hot until, in less that 10 seconds, it would be ice cold tap water.

I'm trying to maximize the effectiveness of the dual elements to create a water supply that does not suddenly switch from hot to cold but instead creates a gradual and bearable decline in temperature. So far... success.

A couple of things to check... Make sure the cold and hotwater pipes are connected properly, and not reversed. You'd be surprised how often this happens. Also, maybe the unit has a broken dip tube? You said it's brand new, but it's possible it came broken. It's brand new so it's not from the 93-97 defective years, but still, worth checking....

Here's a link about broken dip tubes, if you're interested...

»www.rd.com/19441/article ··· 441.html