Water heater running out of hot water

[JLH911]

My home's water heater is running out of hot water in about 10-15 minutes.

I've googled things to look at, but was hoping someone here can give me some ideas as to what it can be.

It sits outside and it's set pretty warm, not HOT but warm and I haven't changed the setting on the thermostat so it's where it's been for the past 6+ years.

The unit itself is probably about 10 years old. It's not leaking anywhere and I drained a little of the water out of it to see if there was any sediment in there but I saw miniscule traces of any type of any.

Whadya guys think?

 

[Capt. Jim]

Gas-fired or electric?

 

[-Spike-]

I'm gonna guess electric, 'cause gas heaters rarely have heating issues.

Check the thermostats. When you run some hot water out, the bottom thermostat should kick on, heating the bottom of the tank. As more hot water leaves and the top of the tank gets cooler, the top thermostat will kick on, shutting the bottom one off. It should stay that way until the top of the tank gets up to temp, then the bottom thermostat will kick back on until the bottom of the tank is up to temp. Check for 220 volts at the elements. An easy way to do this is to turn up each thermostat in turn, it should kick on.

Check the elements. Shut off the breaker, disconnect the wires from the elements, and put an ohm meter across the terminals. You should get something between 10-15 ohms typically, but anything other than zero or infinity should be good.

 

[JLH911]

Doh, Gas.....minor detail.

 

[-Spike-]

Has the water coming into the tank gotten any colder recently? Have you changed any faucets or shower heads? Are you sure there's been a change in the first place? How big is it, and how many people are in the house?

 

[pb4ugo]

It could be a burner or Tstat. Is the water hot when you 1st turn it on? It's probably the dip tube or what ever its called broke. The outlet has a tube going down to the bottom of the tank to supply hot water. Basically, as you use hot water, cold is supplied to the top of the tank, & hot is forced up the tube. If that tube breaks you will get cold water sooner. It's usually is replaceble, if you can get it out. It is getting pretty old.

 

[JLH911]

Has the water coming into the tank gotten any colder recently? Have you changed any faucets or shower heads? Are you sure there's been a change in the first place? How big is it, and how many people are in the house?

Same cold water as always. New Shower head, but it's supposed to use less than the last one but we've been noticing the hot water running out for a month or so now. There's only three of us, six if you count the pups.

It could be a burner or Tstat. Is the water hot when you 1st turn it on? It's probably the dip tube or what ever its called broke. The outlet has a tube going down to the bottom of the tank to supply hot water. Basically, as you use hot water, cold is supplied to the top of the tank, & hot is forced up the tube. If that tube breaks you will get cold water sooner. It's usually is replaceble, if you can get it out. It is getting pretty old.

That tube you mention is what I thought might be the culprit.

Could also be the thermostat, but I'd like to know how to check it first before buying a new one.

 

[PAToyota]

I'm gonna guess electric, 'cause gas heaters rarely have heating issues.

If you don't drain off the sediment regularly (I do mine annually), it will cake up at the bottom of the tank and "insulate" it - making the burner less effective. This tends to be a slow process, though. Not a hot water one week and cooler water the next...

It's probably the dip tube or what ever its called broke.

They had a problem in the mid-90s when the largest manufacturer of dip tubes changed their plastic formula. The dip tubes failed pretty rapidly and in the late 90s there was a class action lawsuit about it. Just because they fixed the formula, dip tubes can still fail over time.

My annual maintenance is to check the anode rod and drain the sediment. A few minutes a year saves on some expensive replacement work. I actually just did my maintenance this week. Here is the picture of the new anode rod (left) and the one it is replacing (right). That is about seven or eight years on the anode and the second one I've put into the water heater. Depending on your water quality, I know people who have to replace their anode as often as every two years and some who get ten years out of them. Best to check them every year to keep the threads free, though. If you let it sit for more than a few years, chances are you'll never be able to get it out of the water heater without damaging something.

 

[-Spike-]

The dip tube is in the cold inlet, sending the cold water to the bottom of the tank. Definitely a possibility. How big is the tank?

 

[JLH911]

So if the dip tube is short(or getting shorter) cold water would be mixing with whatever hot water I'd have towards the top, hence the hot water would seem to run out quick, but in reality cold water is mixing at a level where it should NOT be mixing with the hot water?

 

[JLH911]

I'll check the anode rod.

I just looked up the function of the anode rod. The Anode rod is a sacrificial piece of metal rod that is there to react chemically with whatever type of water(like hard water) is supplying the heater.

If the anode rod is deteriorated or gone altogether, the inside metal lining of the water heater would start to rust up and you'd have all sorts of problems.

I'll check my water heaters anode rod soon.

How do I rule out the thermostat or thermocouple? Would these cause the problem I have?

 

[pb4ugo]

If you allow the water in the heater to come up to normal temp(don't use hot for a while), is the water just as hot as it was b4 the problem? If it is, then I would think the Tstat is working.

 

[JLH911]

If you allow the water in the heater to come up to normal temp(don't use hot for a while), is the water just as hot as it was b4 the problem? If it is, then I would think the Tstat is working.

Good point...yes, just as hot, just doesn't last as long.

 

[PAToyota]

For a gas or oil fired water heater, you want the cold water to go the whole way to the bottom where it can be heated by the burner - and hot water rises naturally, so that works too. Without a dip tube, the cold water comes in at the top and is immediately drawn off to go out to the hot water pipes.

Sort of think of a sprayer in reverse. The sprayer has a "dip tube" connected to the outlet so that you draw from the bottom of the tank. Without it, the fluid level drops and you just spray out the accumulated air. Think of the incoming cold water in the water heater as that air in the sprayer.

Although thermostats can have their temperature setting "drift," it is much more likely for it to stop functioning altogether if it fails. Easy way to check is just to move the adjustment dial. Turn it up - does it turn on? Turn it off - does it turn off? If so, it is likely working close enough to parameters.

The anode isn't going to affect water temperature at all, but - as you found - maintaining it does give the water heater a much longer life than if you ignore it. I've had a number of people tell me a water heater doesn't last longer than four to eight years anyway, so why do maintenance? Well, an anode lasts about four to eight years and if you don't replace it then the tank is next and then - no - your water heater isn't going to last much longer than that. Sort of like saying a car will only last 40K to 60K miles, so why bother changing the oil or doing any service? Actually had someone tell me that... Well, if you don't maintain the car, it is sort of a self-fulfilling prophecy...

 

[Toyo FJ40]

For a gas or oil fired water heater, you want the cold water to go the whole way to the bottom where it can be heated by the burner - and hot water rises naturally, so that works too. Without a dip tube, the cold water comes in at the top and is immediately drawn off to go out to the hot water pipes.

Sort of think of a sprayer in reverse. The sprayer has a "dip tube" connected to the outlet so that you draw from the bottom of the tank. Without it, the fluid level drops and you just spray out the accumulated air. Think of the incoming cold water in the water heater as that air in the sprayer.

Although thermostats can have their temperature setting "drift," it is much more likely for it to stop functioning altogether if it fails. Easy way to check is just to move the adjustment dial. Turn it up - does it turn on? Turn it off - does it turn off? If so, it is likely working close enough to parameters.

The anode isn't going to affect water temperature at all, but - as you found - maintaining it does give the water heater a much longer life than if you ignore it. I've had a number of people tell me a water heater doesn't last longer than four to eight years anyway, so why do maintenance? Well, an anode lasts about four to eight years and if you don't replace it then the tank is next and then - no - your water heater isn't going to last much longer than that. Sort of like saying a car will only last 40K to 60K miles, so why bother changing the oil or doing any service? Actually had someone tell me that... Well, if you don't maintain the car, it is sort of a self-fulfilling prophecy...

What he said, Dip tube. There was a bad batch of dip tubes about 8 years ago that would slowly disolve in water. The were in AO Smith, Rheem and Bradford White. If you flushed the drain you would see small peices of pink plastic.

 

[PAToyota]

There was a bad batch of dip tubes about 8 years ago that would slowly disolve in water.

Actually, it was more like 15 years ago. The last of them were in '97 and you had to have your information in for the class action lawsuit sometime in 2000.

 

[JLH911]

Well....our Heater is an AO Smith, but from around 2003.

I took some pics of the connection on the top and correct me if I'm wrong, but isn't that valve on the top supposed to be on the side where it's labeled Relief Valve?

The port on the side(not pictured) labeled Relief Valve, is plugged shut.

Maybe I'm wrong....

 

[-Spike-]

No, the T&P valve can go in either of those ports. Technically, it should be plumbed outside, or at least to within 6 inches of the ground. That won't affect performance in any way though.

 

[JLH911]

No, the T&P valve can go in either of those ports. Technically, it should be plumbed outside, or at least to within 6 inches of the ground. That won't affect performance in any way though.

But I can move it to the side port, right?

I'm planning on taking out the Anode rod and the dip tube to see what condition they're in this week.

 

[FJ60Seth]

I'll check the anode rod.

How do I rule out the thermostat or thermocouple? Would these cause the problem I have?

if the thermocouple is bad the gas valve won't open. It's a safety switch to keep the gas off if the pilot isn't lit it's not your problem.