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Tanklets > Temperature Fluctuations

Deadband Problem

Q: If no laundry is done in the p.m. (8 hours or less before first shower the next day) the water that comes out of the shower is luke warm. You can hear the water heater kick on while taking the shower, but that first shower is quite uncomfortable. The second shower has warmer water. HELP! Gas water heater, approx. 8 years old.

A: It sounds like you have a deadband problem. That means there is a variation in the function of the thermostat. Sometimes it will think 110 degrees is OK, sometimes 130. That's just an example. It might be any range. The manufacturers do not consider this a defect. You've got a couple of choices. You could buy a new tank, but you'd run the risk of getting another heater with the same problem. The other thing is to run enough hot water in the morning, maybe 10 minutes before you shower, to make the heater fire up. If it's any consolation, my tank does this, too. I just live with it.... -- Randy (12/08/04)

Deadband or Cross Connection

Q: Our hot water heater seems to do a bang-up job of heating the water... except for first thing in the morning. Whoever takes the first shower can't get more than lukewarm water. This was always a problem with our water heater (we bought the house five years ago), but has become much worse (i.e. more consistent and water colder) this summer. I've read a bunch of the posts about cross connections, but I'm not clear about how exactly that happens. Could that be our problem? Occasionally the cold water is kinda warm, but I'd always thought that was just from standing in the line (though it sometimes takes a LONG time to get cold -- longer than I'll wait, often).

A: Yes, a cross connection is always a possibility. There is quite a bit about those under a post by JKV a few down from this one. Another is that you have a deadband problem, where there is considerable leeway in the control. So the control lets the tank cool off more than it ought to before firing to bring the temperature back up to what the thermostat has been set at. I have that myself. Sometimes the water is very hot and sometimes lukewarm. The only fix is a new control or new water heater, however I find that if I run, say, a sinkful of hot water ten minutes before I take my shower, it will "wake up" the water heater and make it fire and the water at shower time will be properly hot. -- Randy (8/22/05)

Q1: I'm still a little confused about what a cross connection is, exactly. The phrase makes it sound like a problem caused by poor plumbing (I think this was JKV's assumption in the post you referenced...), but from the comments to that post, it sounds like it can be caused by a problem at one faucet, as a part wears out. Could someone point me to a reference that describes this problem in more detail? I think I'm going to just go ahead and call a plumber, but I'd like to know what I'm talking about (at least a little) before I do that...

A1: A cross connection means that somehow, hot water is able to enter the cold plumbing or vice versa. Bad plumbing can do it, but so can washing machines, dishwashers and the aforementioned Moen faucets. If you're wondering why I didn't explain all this to JKV, it was because he seemed less interested in solving his problem and more interested in gabbing and we tend to be too busy for that. He might have been a plumber testing us. That happens sometimes. I suggest that instead of calling a plumber, you go back to JKV and do the test described there. It is dirt simple and will eliminate one possibility. Besides, I am almost certain that your problem is the control and the only thing the plumber can do there is replace it or the water heater. -- Randy (8/21/05)

Cross Connection

Q: My gas water heater has previously been diagnosed by The Tank with "deadband" (i.e. bad thermostat). See March 4 posting. However, I am trying to rule out all other variables before replacing an otherwise working water heater. I tried your suggestion of running the water for 10 minutes before showering and have noticed that the water from the bathroom sink is hot. Why would the sink faucet water be hot when the shower water is lukewarm to cold? If bad thermostat then both should be lukewarm/cold right? I then tried flushing the water heater. No visible sign of sediment coming out of the water from the tank, so sediment does not appear to be a problem. I checked the TPR valve. Pressure release worked but now I have constant dripping of hot water from the tank. Any suggestions? Or should I just bite the bullet and buy new?

A: You've done your fact finding. If ANY tap is producing hot water (assuming it all comes from the same heater) the heater is not at fault. It's time you had a look at the shower valve. It is likely a single lever type, probably pressure balanced or thermostatically controlled. You should find the instructions for it and try adjusting to see if the problem can be fixed there. There may be a phone number to call for technical help as well. Your heater should get a new T&P and possibly anode, but otherwise is OK. Let us know how it goes! -- Larry (4/06/05)


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