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dcmalj · Nov 13, 2008, 11:22 AM

What would cause a gas water heater to suddenly put out lukewarm water? The pilot light is on, the burner (or whatever it's called) comes on when we turn the knob to increase the temperature, and we can raise the temperature a bit by turning the temp setting higher, but it never gets really hot.

The heater is, I think, 10+ years old but worked perfectly until two days ago. Any thoughts?

massplumber2008 · Nov 13, 2008, 05:07 PM

Hey Dcmalj...

I 'm going to bet that the DIP TUBE has gone defective... see picture below.

Here, if the dip tube has fractured or clear broken off then cold water would not flow into the bottom of the heater as it usually does (via the dip tube) and rise to top as it becomes heated. Instead, cold water would flow into the hot water so when hot water is called for you get a mix of hot AND cold... leaving you with a warm water instead of hot water.

Anyway, to check this, begin by turning the gas valve to pilot setting.

Second, shut the cold water shutoff into the water heater. Then open the hot water only to all two-handle faucets in the house (do not open valves with single handles) and drain the water heater enough to get water below the inlet/outlet of heater.

Then you will need to cut the cold water inlet pipe to heater or disconnect union fitting if present and then you will need to remove the water heater COLD NIPPLE. After this nipple is removed you will need to look inside the tapping of the water heater to see if you can see the tube down inside the tapping. If so, then grab the dip tube with a pair of needlenose pliers and check condition.

Dip tube should be at least 1/2 as long as the tank is tall... hopefully, dip tube is even longer... ;) Check for cracks as well.

If dip tube is defective then you should just need to go to a home supply store or a local plumbing supply store and ask for a replacement dip tube. You will also want to get a roll of 1/2" teflon tape, 1-3/4" dielectric nipple, and a 1/2" or 3/4" sharkbite type coupling (to join copper where you cut it).

To replace, you just drop dip tube and washer (if included) into tapping... it shouldn't fall in... and then wrap nipple 6-7 times with teflon (clockwise), install nipple, re-install copper pipe and then use the sharkbite coupling to join the cut copper (if cut).

Fill the water heater with water, purge water/air from faucets, turn the pilot control to on and you should be back in business.

If not the dip tube then it could also be the gas valve.. but I'm betting it's the dip tube... ;)

If heater is on its last leg then you may consider just replacing the heater... you will know best here.

Let me know what you think...

MARK

mygirlsdad77 · Nov 13, 2008, 05:14 PM

Very good advice you got from mass. Detailed description of replacement of dip tube, and a 99.9 percent chance that this will cure your problem.

afaroo · Nov 13, 2008, 10:25 PM

Hey Dcmalj,

I agree with Mark and I am adding the following link to show you how the Dip Tube works, Thanks.

John

How a water heater dip tube works and what it looks like.

Milo Dolezal · Nov 13, 2008, 10:28 PM

It may also be faulty thermostat and / or crossed pipes. Any plumbing work done in your house recently ?

mygirlsdad77 · Nov 14, 2008, 05:39 PM

Originally Posted by Milo Dolezal

It may also be faulty thermostat and / or crossed pipes. Any plumbing work done in your house recently ?

On a gas unit, the thermostat is a probe attached to the gas valve, therefore the gas valve would have to be replaced(parts on gas valves are not replaceable(as far as I know)) As far as crossed piping(cold water supply going into the hot water outlet of the water heater, and hot water supply coming out of the cold inlet of water heater) milo is dead on. This would cause shortage of hot water. But you should still get a couple of minutes worth of hot water before it becomes lukewarm.

afaroo · Nov 14, 2008, 06:44 PM

Attach are the pictures of a thrmcouple and the gas heater gas valve,Thanks.

Regards,
John

mygirlsdad77 · Nov 14, 2008, 06:56 PM

Good visual. But doesn't show the temp sensing probe(themostat) that comes out of the back of the gas valve and into the water heater. This part is not replacable(as the thermocouple is). You would have to replace whole gas valve. But I still believe it is most likely a defective dip tube. Cheap easy fix, compared to gas valve replacement. On a water heater this old, if the dip tube doesn't fix your problem, I would seriously look into replaceing the water heater. Going to hurt if you start dumping money into a ten + year old water heater, just to have the tank start leaking a week later. No fix for a leaking tank.

afaroo · Nov 14, 2008, 08:03 PM

Mark and myself have said it from the beginning that it will be the drip tube, the rest is just and info, see the images below will show you the compnents for the water heater, Thanks.

John

Milo Dolezal · Nov 14, 2008, 10:05 PM

Originally Posted by mygirlsdad77

On a gas unit, the thermostat is a probe attached to the gas valve, therefore the gas valve would have to be replaced(parts on gas valves are not replaceable(as far as i know)) As far as crossed piping(cold water supply going into the hot water outlet of the water heater, and hot water supply coming out of the cold inlet of water heater) milo is dead on. this would cause shortage of hot water. but you should still get a couple of minutes worth of hot water before it becomes lukewarm.

I was recently asked to trouble-shoot plumbing problem in apt. building owned by my friend. Problem: hot water is suddenly warm, not hot, and temperature widely fluctuates from warm to cold. What I found out was following: She had a handy man remodeling one of her apartments. He replaced shower valve with new, Delta, single handle unit. This faucet comes assembled with dummy cartridge. Actual cartridge is in separate box and is to be installed after all soldering have been completed. Well, handy man just left the dummy cartridge in and planned to install real cartridge when entire project is finished. Since the cartridge was dummy, it had no interior passages and simply opened hot water to cold and vice-versa. Took 5 minuter to slip-in real cartridge - and problem was gone. Warm hand-shake followed...

afaroo · Nov 15, 2008, 07:14 AM

Hi Milo,

I agree with you in your case there was something done to cause the problem, but dcmalj has said nothing that he have replaced that's why I would think of the drip tube may be my guess is wrong it will be something else let see what will be the out come, Thanks.

Best Regards,

John

mygirlsdad77 · Nov 15, 2008, 04:46 PM

Originally Posted by afaroo

Mark and my self have said it from the begining that it will be the drip tube, the rest is just and info, see the images below will show you the compnents for the water heater, Thanks.

John

Sorry, I knew that you two had originally advised checking dip tube. I was just trying to let the asker know that your advice was correct. ( I should have said... check the dip tube as mark and afaroo suggested) but I got ahead of myself. I enjoy the extra info that everyone gives, gives me a chance to learn.

afaroo · Nov 15, 2008, 06:48 PM

Mygirldad,

Its all right the more info the better we all learn something new every day keep up the good job you are doing excellent, good luck.

Best Regards,
Jon

dcmalj · Nov 17, 2008, 11:52 AM

Thanks so much to everyone who took time to answer! We have temporarily mitigated the problem by just turning the heater all the way up and have been so busy with other things that I didn't get back right away to check for replies. We'll take a look at the dip tube and I'll let you know what the outcome is.

Thanks again!