Brain Teaser

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Jerry KES

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Bloomington, In.
2 years ago I was hired to rewire an old house. Before we started the homeowner walked me through a few of the problems he was having. One of the problems was: Everytime he flushed the toliet, the kitchen lights would go out until the tank would fill up and the lights would come back on. The toliet was feed w/ hot water. I saw this for myself, but since we rewired the house, I never spent the time to troubleshoot and find out the problem. I have an idea, but I would like to hear what you guys think.
 
they fed the toilet with hot water? was the water heater electric? i wonder if somehow when the water heater turned on it caused the lights in the house to some how go out maybe do to a loose connection in the panel?

whats the answer
 
There was a well pump connected to the kitchen wiring circuit. When the toilet flushed,the pressure drop kicked on the well pump, causing the lights to go out.
Or something similar.
 
The toliet was feed w/ hot water. I never found out for sure what the problem was, thats why it has bothered me for the last 2 yrs. It had to have something to do w/ the water heater. It was in the city so there was no well pump.
 
I would have wanted to know if any other water-related action caused the same problem. For example, did the kitchen lights go out while the washing machine was drawing water, and did it happen only when the washer was using a hot water cycle?

I don't think the water heater doing its thing of making cold water become hot water can be related to this symptom. There is always a time delay before the water heater starts heating, and it takes time for it to finish its heating cycle. The toilet flush takes far less time to complete its cycle.

You say you observed this? Just once, or did you test it several times? Was it consistent? Did the kitchen lights come on the moment the tank was full, or was there a time delay? Was it all the lights in the kitchen, or just one? How did you observe this (i.e., were you standing in the kitchen and were you close enough to the bathroom to hear the flush cycle)?
 
We did it a couple of times because I could not believe what I just saw. The renters that lived there just delt with it for some time. From what I remember there were 2 surface mounted lights in the kitchen and when we would flush the toliet the lights would totally go out. Not just dim. When the water quit running to the tank the lights would come back on. The house was in the city and I assumed they were on city water, but after I got a response inquiring about a well pump I checked with an older builder in town today and he said some of those old houses still have an active well. That makes sense.
 
Good questions charlie. I pondered an instant water heater on the kitchen circuit.

Also: Are there any leaks? Like for a nail through the drain through a wire type scenario?

I tried to picture a short to the plumbing pipe that was jostled by the running water but I would expect more of a flicker than a dim with a delayed return once the tank was filled.

Is there a heater in the toilet tank, electric seat, etc?

All the good guesses are being shot down by the data.
 
mivey said:
Good questions charlie. I pondered an instant water heater on the kitchen circuit.

Also: Are there any leaks? Like for a nail through the drain through a wire type scenario?

I tried to picture a short to the plumbing pipe that was jostled by the running water but I would expect more of a flicker than a dim with a delayed return once the tank was filled.

Is there a heater in the toilet tank, electric seat, etc?

All the good guesses are being shot down by the data.
Click to expand...

How about the lights were not loosing power, but the return back to the panel. I have seen alot of grounds used as neutrals in old houses.
 
I think the hot water aspect has lead to a red herring by making everyone think about the water supply, but forget about the water drain.

My guess is that somehow the water in the drain could be shorting out the supply circuit before it gets to the kitchen, resulting in the lights not getting sufficient voltage to light.

There could be countless specifics though. One thought is that the hot is shorted to a metal drain line, but that section of the line is isolated with rubber couplings. When water is present, it completes a circuit across the rubber, thereby grounding the normally isolated section.

Another, slightly more probable situation is that the wire is actually running through the water, either right in the pipe, or in a pool caused by a leak.
 
Is it possible the problem is related to the weight of the tank instead of water flow?

After the tank has filled and the lights come on again, what happens if you reach in the tank and push the float down to force the water on? If the lights stay on, then it's probably a weight problem. If they go out, then a water flow problem.

Also, if it is a weight problem, trying to lift the tank by hand should dowse the lights.

If it is a water flow problem, does it have to do with the water supply or drain?

Rick Christopherson said:
My guess is that somehow the water in the drain could be shorting out the supply circuit before it gets to the kitchen, resulting in the lights not getting sufficient voltage to light.
Click to expand...

If the water is shorting out the lights to the point where they go completely off, then wouldn't the breaker trip?
 
The funny thing is I just talked to a guy about a week ago that had this problem and he said it was a wire that had a drywall screw threw a romex into a water drain. It was a "I had this problem", but we never got to how he figured it out...

Try testing other outlets or lights on the circuit while you flush the toilet.
 
Sounds like a handymans nightmare.

How about if during one of these remodels someone actually hooked up the hot water line to the toilet?

Now that know we have such qualified professionals on the job I am sure that finding a black and white in the pressure switch sure would make the lights work while it was open and go off when closed.
 
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