Strange hot water problem! Help a newbie!

Hi all,

We just moved into the top two floors of a brownstone in Harlem. Exciting stuff, however, I am starting to realize what life without a super is really like. I'm a novice when it comes to plumbing and here is our first problem! Any feedback would be really appreciated.

When we run the hot water in the bathroom it runs boiling hot for about a minute and then cools right down to luke warm temp. Turning off the tap, waiting a minute, then turning it back on results in the same thing. Runs really hot for 30 seconds or so, then goes warm. It does this over and over again!

I got a handyman/plumber guy in to take a look and he couldn't really tell if there was a problem with the water heater or boiler. He said the water in the heater seemed to be really hot. The thermostat on the heater wasn't quite at the max, so he turned that up all the way and said it might help, but again he didn't really give a definitive answer as to what was causing this to happen. He also added that replacing the thermostat might help.

Any ideas folks? I know absolutely nothing about plumbing and would be so grateful for a bit of advice.

It is a 40 gallon gas heater (in the basement, we are on the 2nd & 3rd floor).

Cheers all

Does it only happen at one fixture? What brand of fixture? Almost sounds like your cold is mixing with the hot in the valve, I've heard of shower valves doing that.

Cranking up the heater usually isn't the answer and can be a bad idea in itself. Get a plumber, not a handyman.

kissiffer4 said:

When we run the hot water in the bathroom it runs boiling hot for about a minute and then cools right down to luke warm temp.

Turning off the tap, waiting a minute, then turning it back on results in the same thing. Runs really hot for 30 seconds or so, then goes warm.

It does this over and over again!

It is a 40 gallon gas heater (in the basement, we are on the 2nd & 3rd floor).

Click to expand...

Your vertical pipe only contains a 1/4 gallon or so of water, so I don't think this is it.

Since the whole cycle doesn't take long, have an assistant feel the hot water pipe at the WH in the basement while you have it go through several hot/cold cycles.
Collect the hot water in a container so you know what volume you are dealing with.

If the pipe at the heater stays constantly hot you need an Exorcist or some valve is mixing hot and cold.

The time it takes for it to go hot to cold at whatever flow rate you're using may be a clue as to how far from your tap the problem is occurring.

Does it get hot again if you leave the water running?

Is it a single handle faucet?

fregzius said:

Hi this is Fregzius.
I shall be thankful of yours if you will guide me that I have just renovated my bath and now I am having problem with getting the hot water as I have removed the connection from there and I have made it myself. So please any body knows the exact connection of that.
Thanks and regards.

Click to expand...

You would be better off to start a new thread with your problem and with better details of your issue. Pictures can also help.

This is going to sound rediculous and you pros out there are going to laugh me off the website, but I saw this problem once before. The water heater was hooked up backwards! The hot water was being tapped from the cold side of the water heater which has a tube going to the bottom of the tank so that the cold water refill doesn't splash on top of the hot. The water was hot for a few seconds and then the cold refill water was directed into the hot water pipe. Instead of taking the hot water off of the top of the tank the user got the cold water, mixed somewhat with the hot water in the tank as it settled to the bottom.

No T Cox,
I wouldn't laugh at that it happens...
Been in the trade long enough to know anything is possible...

I would recommend getting the handyman out of the equation though...
Turning up the t-stat is always their answer even though it is the worst answer...

Could also be a bad dip tube or, tempering valve a plumber on-site should be able to figure it out...

Since you admit you are a novice, perhaps a short water heater primer is in order. Cold water enters the tank at the top, but it is heated at the bottom. In order for this to happen, directly below the intake at the time there is a tube called a dip tube that conducts the cold water to the tank bottom. Hot water rises and therefore is at the top of the tank. When you open a hot water faucet, it is the entering cold water at the bottom that forces the hot water out of the top of the tank. If the dip tube is broken or the cold and hot lines are reversed, the water will be hot at the top but will not last long. It should be easy to see if the lines are reversed, the intake and outlets are marked on the tank Hot and Cold. It is not likely that the dip tube is broken, there was a period of time several years ago that there were problems, but that was taken care of. As others have said, use a licensed plumber instead of a handyman. Handymen are noted for having very limited knowledge. Don't hesitate to use this forum for assistance on DIY jobs, we also will advise you when we feel you may be attempting something beyond your skill/experience level and suggest you hire are plumber.

Gary,

Good description, but it is probably best to clarify that heating of the water occurs on the bottom head of the tank and through the central chimney. The twisted baffle in the chimney keeps the hot gas swirling against the walls of the chimney until it exits. (Without the baffle a thick cool boundary layer would slowly move up the wall while a hot central plume would shoot up the chimney with considerably less heat exchange. I've seen this sort of problem in process designs, particularly double pipe gas preheaters.)

As you say, most of the heating will occur in the bottom third of the tank. The final 2/3 is there to improve the efficiency/drop the flue gas temperature. This is most apparent with a fully cold tank. The flue gas is cooled so much that condensation occurs, drips back onto the burner and causes a yellow flame for a few minutes. If the system was set up to remove the condensate to a drain (rather than drip onto the burner pan) so that the flame remained blue and the condensate wasn't eventually re-vaporized and sent out the stack, the efficiency of the tank would be considerably improved. Of course then various components would have to be able to handle the acidic condensate...

hot water

You either get a handyman, or you get a plumber. There is no such thing as a handyman/plumber, and in this case you had a handyman. A plumber would have checked your recirculating system, since I am sure that building has one, and might have found either a dead pump, or a bad check valve, or both. When the water is shut off the circulation system brings hot water to your faucet. But when you open the faucet, the dynamics are such that it is easier for cold water to flow directly to the faucet through the malfunctioning return line, than to flow the normal way and push hot water ahead of it, so you faucet water turns cold almost immediately.